Download Gerbera Growing Manual - Rise n` Shine Biotech

GERBERA MANNUAL
Complied By
Rise n` Shine Biotech Pvt. Ltd
Corporate Office :301,Metro House, Mangaldas Road, Pune: 411001, Maharashtra, India.
Tel: +91-20-26165268, Telefax: +91-20-266809800
E-mail: [email protected]
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Tel: +91-20-66785700, Telefax: +91-20-66785700
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INDEX
i.
ORIGIN AND CHARACTERISTICS
ii.
SOIL ASPECTS
iii.
CULTIVATION
iv.
CLIMATE
v.
HARVESTING & PACKING
vi.
PEST CONTRIL & DISEASE
vii.
PREVENTION
Edition: 2010
RISE n’ SHINE BIOTECH PVT. LTD.
GERBERA GROWING GUIDE
1. ORIGIN AND CHARACTERISTICS
Edition: 2010
RISE n’ SHINE BIOTECH PVT. LTD.
2. SOIL ASPECTS
Airiness
The percentage of oxygen in the soil is very important to the gerbera. It needs to be
relatively high, as it is necessary for the aeration of the roots. The roots are sensitive to an
environment lacking enough oxygen. In the summer especially, the plant needs higher
doses of oxygen because of increased respiration.
It is important to have good soil texture during cultivation, which means approximately 1/3
medium, 1/3 air, and 1/3 moisture.
Soil layers and structure
Gerbera roots can grow extremely deep into the ground. The deeper soil layers, therefore,
need to be without a hard pan.
Every type of soil (clay, sand, etc.) has its own structure. To improve airiness, (aged) organic
material such as tree bark, straw, peat, perlite or (cooked) rice hulls, can be mixed in the
top layer that is approximately 30 cm deep. In addition to increased airiness, it also
improves the moisture in the soil.
Ground water level
A temporary high level of ground water often results in rotting of the roots, which causes
the plants to die. Tests to check the water level need to be done to find out the exact level.
It might be necessary to develop a closed-drainage system at 70-80 cm deep.
2.2 Water and Soil analysis
Before planting or even preparing the beds, a soil sample needs to be taken to obtain
information about the condition and profile of the soil. It is important to look at the pH level
(acid level), EC level (salt) and the amounts of macro- and microelements.
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The target values for a soil sample are as follows:
Range gerbera cultivation in soil Macro elements
(1:2 volume-extract, elements in milimol/liter)
Value
pH
EC
N
P
K
Mg
Ca
S
Na
CI
Target
6
1.0mS/cm
4
0.2
1.5
1.2
2.0
1.5
<2.0
<2.0
Low
5
<0.5
2
0.1
1
0.7
1.0
0.7
0
0
High
7
>2.0
>8.0
>0.4
>2.5
>2.0
>4.0
>4.0
>4.0
>4.0
Range gerbera cultivation in soil Microelements
(1:2 Volume-extract, elements in micromole/liter)
Value
Fe
Target
12
Mn
1.5
Zn
B
2
Cu
12
1
Nutrients
The plant is able to absorb all the elements at a level between 5.5 and 6.0. A high pH level
will cause problems with absorption of some elements (Mg and Fe), which will result in
deficiency symptoms (like yellowing of the leaves), while there are enough of these
elements available in the soil. A low pH level mainly causes a change in structure. To
increase the pH level calcium can be used. To decrease it, Alkali products can be used
(HNO3, NH2NO3, H3PO4) or the soil can be mixed with Alkali peat products.
The salt concentration in the soil needs to be low enough. It might be necessary to flush
the soil with clean water before planting. Take a second sample after doing this to obtain
new information about the condition of the soil.
With a low EC or a shortage of a certain element, the best solution will be to use
fertilization. Before planting, a basic fertilization schedule can be applied. For this, organic
material or fertilizers (or a combination) can be used. When using organic material use the
proper organic material, such as tree bark, hay or manure. Don’t use chicken manure
because it contains urea, which is very aggressive for the plants. Always apply organic
fertilizer before disinfecting the soil.
Water quality
Even more important than the quality of the soil, is the availability of high quality water.
Rain, city, or well water can be used for watering gerberas. The gerbera crop is very
sensitive to salt; the lower the level of salt, the better.
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Ranges (target numbers) water gerbera macro elements (milimol/liter)
Value
PH
EC
N
P
K
Mg
Ca
S
Na
CI
Low
6.5
0.2
0.1
0
0.1
0.2
0.5
0.1
0
0
High
7.5
0.7
0.2
0.1
0.5
0.5
2.0
1.0
2.0
2.0
Ranges water gerbera microelements (micromole/liter)
Value
Fe
Mn
Zn
B
Cu
Low
High
1
25
1
2
1
2
1
5
0.1
0.5
The water needs to have a pH of 5.5 – 6.0. Sometimes the water needs to be preheated
when the temperature is lower than 15C. Purifying or “de-salting” by using filters, reverse
osmosis, disinfecting, or “de-ionizing” can improve the water quality1.
Have sufficient water available; the maximum need can increase up to 3-liters/m2/per day
or 30m3/ha/day for cultivating the gerbera crop in soil.
2.3 Soil sterilization
It is of crucial importance to always disinfect the soil before planting your gerbera crop.
Fungus and Nematodes in particular can cause serious problems when skipping this step.
Soil can be disinfected several ways.
Methyl bromide
This method is effective and relatively cheap. However, in many countries (in particular the
ones were the soil water level is low) the use of methyl bromide is not allowed because of
its dangerous effects on the drinking water.
Steaming
Very important is that the soil needs to be dry before steaming. With the use of heavy
plastic covers or drainpipes, the soil will be heated for 6-8 hours by blowing steam
underneath the covers. When using drainpipes, the results are better because the pipes
are placed deeper in the soil.
There are many other ways to sterilize the soil (Vapam, Chloorbromide, Basamide, Rizolex)
that often don’t have the same results as steaming or using methyl bromide.
1
Try to avoid using 100% osmosis water, a combination of reverse osmosis with normal water (e.g. rain water)
will result in a more stable water quality.
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3. CULTIVATION
3.1 Planting time
Time of planting depends on your specific situation (soil type, planning, supply and
demand) and climate, in particular temperature and light intensity. How long you would
like to keep the crop also is something to keep in mind. In principle it will be possible to
plant a new crop year round. However, depending on the continent, certain periods are
more preferable. It is recommended not to plant during very warm weather with a low
humidity.
The economical cultivation time of the gerbera is two years. In the second year, the
regularity of the production and quality of the flowers decline. Under the right
circumstances, it is possible to cultivate the gerbera plants for several years but because
of the economical time span the standard is to replace the crop after the second year.
3.2 Planting methods
It is most common to plant on elevated beds with two rows of plants per bed. This way the
drainage is better, heating can be achieved faster, and the foliage is able to open up more,
thus creating more light in the center of the plant. In addition, it is easier to work with the
crop. After sterilizing and drying of the soil, the elevated beds can be created by hand or
with special equipment.
The width of the bed is approximately 60 centimeters (depending on a 4,5 or 6 row
system), which includes the sloped side. The elevation difference between the paths and
beds is approximately 30 to 40 centimeters. The distance between the plant row is 30-40
centimeters.
The plants are grown 25-30 cm apart (triangle). This results in 6.5 to 7.5 plants per m2.
This number of 6.5-7.5 plants per m2 includes all walkways and paths in the greenhouse.
Planting
It is best to plant Gerberas in moist beds. It is recommended to immerse the plants in a
container with water (possibly with fungicides) to soak up some water. The best time for
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planting is during the cooler periods, early morning or night. Don’t plant too deep. The
centre of the plant has to stay approximately 3 centimeters above the soil level. During the
growing process, the heart of the plant will be pulled slightly into the soil. Pay extra
attention to your crop when the first flowers appear.
Planting
jiffy
2 – 3 cm
Immediately after planting, water the plants over the top. This will result in a high relative
humidity around the plant, which is necessary during this first growing phase. Keep the
soil moist until the plants have developed enough foliage and can build up its humidity. It
is recommended to protect the young plants against too high temperatures or light
intensity (>500 watt/m2 or 45,000 lux) by shading. Optimum temperatures during this
phase are 20-22 ºC soil temperature and 20-22/20-25 Night/Day temperatures in the
greenhouse. The temperature shouldn’t drop below 15ºC during the first month. After 4
weeks, when the first flowers will show, the climate and watering changes.
3.3 Irrigation
After the first few weeks (1-4 weeks depending on the starting material and growth speed)
of watering overhead, the watering system changes to watering from underneath the crop.
This normally starts when the plants have 5 to 6 full grown leaves.
Watering underneath the crop can be done with drippers and polyethylene or regular pipes
that are located on the ground. Watering is kept to a minimum in controlled doses per
plant. As a result, the crop remains drier.
Watering systems
When developing a watering system, several factors need to be kept in mind. First the
location of the main pipe (cool, flat, underground). Second, usage of filters to prevent
blockage. Third de-ionizing the water. Fourth, the length of the pipes (maximum 30-40
meters). Fifth, leveling the area. And sixth, the capacity of the pumps, taps, and the area
that every facet needs to cover. The main line is usually installed above or below ground
along the perimeter of the greenhouse. From there the drip lines can be attached. The drip
line is located in the middle of the bed between the two rows with drippers for each plant.
In most cases, watering will be dosed at 2 liters per hour per point at a pressure of ½ bar.
The pipes and drippers have to be cleaned regularly to prevent blockage. Make sure you
use filters at the point of entry. Filling them for 24 hours with a 3% CI and/or 3% No3
solution can do this. After doing this, it will be necessary to flush thoroughly with water.
There are several substances on the market that can be given in small doses with the
regular dripping-program during cultivation. Severely blocked drippers and pipes need to
be replaced. Check the amount of water and difference per dripper on a regular basis.
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Watering
Due to the differences of watering systems and the needs of the plants, it is difficult to
indicate exactly how much water the crop needs. In addition to the watering system, factors
such as climate, soil type, cultivars, and growing phase, play an important role. Check the
moisture level in the soil regularly. It is important to check especially at a deeper level. Use
a soil augur or dig a hole in the bed and feel if the soil is slightly moist. The frequency of
dripping varies. A frequently used irrigation scheme on heavy soil is to water once or twice
a week in two times during the morning hours. On lighter soil two to three times a week
once a day. It is recommended to start watering early in the day, approximately 1 hour after
sunrise. If necessary, additional water can be given up to 3 to 4 hours before sunset. A
rough estimate is to give an average of 550 to 650 liter per m2 per year. Less water is
given in the winter periods (months with less light). Usually nutrients and chemicals for
disease control are mixed with the water. It might be necessary to flush the soil during
cultivation when the EC of the soil is too high. This can be done by giving about 2-3 hours
of clean water (water with low EC).
Water temperature
It is recommended to keep the water temperature the same as the daily temperature. The
minimum temperature should be 15ºC. Temperatures that are lower could cause root
diseases. When water temperatures are higher than 30ºC, the oxygen level will decrease
too much. This can partially be prevented by keeping the water moving in the tanks or by
adding air to it. Heating the water occurs in outside tanks (by the sun) or you may also
install heating tubes in the tank. Avoid large variances in water temperature.
3.4 Fertilization
Fertilization is needed during cultivation to maintain growth and production. As a base for
your fertilizer program, regular (preferably once a month) soil sample analysis is used. The
values mentioned in chapter 2.2.2 can be used as your goals during growing.
The most used fertilizer system is the system using a separate A and B tank in which the
miscellaneous concentrations of fertilizers are being dissolved. Based on both the soil and
water analysis it can be calculated how much fertilization needs to be given at certain
times. The reason for using two separate tanks is that some elements in a concentrated
form can cause a precipitation (i.e. Calcium and Sulfate). By using an automatic dosing
system2 (i.e. an injection system with pH and EC control) both solutions will be mixed with
water and given to the plant.
2
If an automatic dosing system is not available, one time give the A-solution and the next time the B-solution.
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Basic Fertilizers used with an A and B tank system
Tank A
Tank B
Main Elements
Calcium Nitrate (CaNO3)
Main Elements
Potassium Nitrate (KNO3)
Mono Potassium Phosphate
(KH2PO4)
Potassium Nitrate (KNO3)
Ammonium Nitrate
(NH4NO3)
Magnesium Sulphate (MgSO4)
Potassium Sulphate (KH2SO4)
Trace Elements
Trace Elements3
Iron Chelates 6-10%
Manganese Sulphate (MnSO4.H2O)
Zinc Sulphate (ZnSO4.7H2O)
Borax (Na2B4O7.10H2O)
Copper Sulphate (CuSO4.5H2O)
Sodium Molybdate (Na2MoO4.2H2O)
Instead of using an A and B tank system, a simpler (but less accurate) way is to create a
large reservoir with an unconcentrated solution. The most simple (but least accurate) way
of giving fertilizer is the use of the formulated (NPK) fertilizers. Generally speaking a
formulation of NPK 20-20-20 until flowering can be used and NPKCaMg of 15-10-30-102 during flowering.
3.5 Nutrient characteristics
Magnesium:
Magnesium is very important for chlorophyll. Lack of Magnesium can have different
effects. Yellowing of leaf tips, while veins remain green. The leave feels thicker and crisper
and the young leaves show signs of necrotic spots.
Iron:
Lack of Iron leads to young leaves turning yellow, but veins remain green. In severe cases,
a white/yellowish color occurs between the veins. Lack of Iron uptake of the plant often
coincides with high pH levels around the roots.
3
In soil culture Micro elements can also be given with a regular foliar spray.
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Phosphate:
Is important for the root development. Deficiency symptoms are, old leaves turn a
purple/red color, often concentrated at certain spots and signs of poor root development.
Nitrogen:
Has its effect on the foliage growth. Deficiency symptoms are overall yellow coloring and
decrease in foliage growth. Too much Nitrogen gives low flower production and a lot of
leaves.
Potassium:
Is important for the stem length. Deficiency symptoms are discoloring of the foliage starting
at the tips and earlier loss of foliage. Leaves and flowers are short and wilting.
Chloride, Sulphur and Ammonium
Chloride is important for the generative growth and quality of the flowers, Sulphur gives
defensibility against mildew and Ammonium is a pH regulator.
3.5 Crop Maintenance
Maintenance of the crop is very important, especially in crops older than a year.
Maintenance starts in the very first period of cultivation by taking out the first buds from
the new plants. The first flowers are usually of poor quality. Taking these first buds out will
quicken the vegetative start of the plant. This way the new bud will have enough support
of the plant to produce a good quality flower. Normally you take out the new buds until the
plant has 12 leaves.
After the first period, maintenance consists of removing old leaves and opening up the
center. When removing old leaves make sure that you only remove the dead leaves and
that you don’t take out new leaves4. Opening up the center is done by bending the leaves
from the heart of the plant.
On average these two activities need to be done once every month.5
4 CLIMATE
4.1 General
During cultivation light, temperature, humidity and the level of Carbon Dioxide determine
the growth of the Gerbera plant. In general you can divide climate into Micro and
Macroclimates. In which the microclimate stands for the climate in and surrounding the
plant. Macroclimate stands for the climate in the controlled Greenhouse.
4
5
On certain varieties good leaves need to be removed to maintain a 3.5 Leaf Area Index (LAI)
If time is a limiting factor an alternative is to use a hedge trimmer to cut off the old leaves.
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An important aspect is that the Microclimate around the plant is affected by the
Macroclimate in the Greenhouse but normally is not equal to the Macroclimate in the
Greenhouse.
4.2 Light
Light gives the plant energy that is necessary to create sugars for growth from C02 and
water.
The light aspect of growing can be divided in two parts; light intensity and day length. The
gerbera is a so-called quantitative short day plant, meaning that during a short day most
buds are being formed.
In regards to light intensity the following rules apply. High light intensity with higher
temperatures result in faster growth. Too high light intensities or sudden changes in light
intensity however can lead to burning of foliage or wilting symptoms (plant temperature
increases too fast and the plant is unable to absorb enough water for respiration).
Higher light intensity also results in a more compact growth, shorter stems, and often a
more intense flower color. Shading or putting white wash on the roof can prevent these
effects of high light intensities. Shading is recommended when light intensities are
approximately 650 watt/m2 or 60.000 lux. During the darker periods, take as much
advantage of the light as you possibly can to increase your production. In this period 1%
more light will result in 1% more production. A clean roof, a lighter greenhouse, and no
shade cloth will all contribute to a higher light intensity.
In The Netherlands where light intensities are low during the winter, assimilation lights are
used to get higher production and better quality. Although the lighting results in higher
production and better quality because of the high cost of putting assimilation lights it is
not yet proven to be profitable.
Light is measured in different units, most common are Klux and W/m2, both measure
different aspects of light (Klux the visible light and W/m2 light used for photosynthesis).
The following table can be used to compare the two units.
Source
1 Klux = ….. W/m2
Daylight on dark day (25 W/m2)
24
Daylight on lighter day (300 W/m2)
14
Daylight on light day (600 W/m2)
11
Daylight on sunny day (1000 W/m2)
10
Light bulb (150 W)
4.2
The other unit being used is J/cm2.hour, which corresponds with 2.778 W/m2.
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4.3
Temperature
Air temperature
The optimal growing temperature depends on the light intensity and time of year. For the
different seasons the following optimum temperatures can be recommended.
Season
Av. Day temp
Av. Night Temp
ºC
ºC
Summer
24-26
18-20
Fall
21-24
16-18
Winter
19-22
14-16
Spring
21-24
16-18
The different seasons coincide with periods with different light intensities (winter season
with the lowest light intensity and summer with the highest light intensity).
The gerbera plant is a sturdy plant, which can stand a wide range of temperatures. For
commercial growing there are however certain important temperatures. The minimum
average daily temperature for maintaining sufficient production is 16ºC. The minimum
temperature for having production is 7ºC. Temperatures below 7ºC stops the formation of
buds and the chances of root diseases increase. Freezing temperatures (below 0ºC) will
cause the plants to die due to frost.
Temperatures higher than 30ºC will also slow down the formation of buds. The absolute
temperature is 42ºC, above this plant loss will occur due to destruction of plant proteins.
Root temperature
Besides the air temperature the root temperature is at least as important. A sufficient high
root temperature keeps the roots active and stimulates absorption of water and elements.
When the root temperature is low compared to the air temperature, the plant is unable to
absorb enough water for evaporation. A higher root temperature is also important for a
healthy root system and the development of new roots. When it is too high, however, there
may be problems because the plant is unable to evaporate enough.
Optimum root temperature is around 21ºC. Be careful not to get temperatures lower than
10 ºC or higher than 30ºC.
When working with a climate computer in the greenhouse the so-called dead band (the
difference between heating and cooling set points) needs to be between the 0.5 and 3ºC.
The most important source of energy for heating the greenhouse is the sun. In areas
and/or periods when this is not sufficient, there are several options to heat the
greenhouse. Several fuels can be used, such as gas, oil, coals and woods. Heating can be
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split into three main areas: (1) ground heating, (2) crop heating and (3) air heating. Ground
heating stimulates the roots. Crop heating will contribute to a good evaporation and
microclimate. Heating of the upper part of the greenhouse will help with transport of
moisture and creates a good macroclimate. Heating pipes with warm water are used for
ground, crop and air heating. Air heating can also been done by hot air canons, fires etc.
Another option for obtaining higher temperatures in the greenhouse is energy cloth. A
“double room” effect is created and because of the isolation the temperature in the
greenhouse rises. It also decreases the amount of light (lower production), which is the
reason why most energy cloths are not used during the day.
Cooling
Ventilation is necessary when the temperature rises too much. Ventilation is done mainly
by top venting and/or side venting. Best result can be obtained with the so-called “chimney
effect”. Open large top windows and smaller side windows. This can also be obtained by
using fans. Shading will help to maintain the temperature stability, because the plant
temperature will increase less quickly due to the blocked light intensity.
The volume of the greenhouse is also important. The larger the volume, the smaller the
changes and the easier it is to control the climate. The best option is high and open spaces.
In tropical climates, other cooling methods are used, varying from the pad and vent system
to high-tech air conditioning systems.
4.4 Carbon Dioxide
The plant uses CO2 together with water and light energy to generate its “basic sugars”.
These sugars are partially used for the growing process. When light intensities are high
and water is sufficiently available CO2 can be the limiting factor for growth. High light
intensity often goes together with high temperatures and thus increased airing. This
causes the CO2 to escape the greenhouse, rather than providing it to the plant. In these
cases CO2 enrichment will enhance production and quality.
The CO2 level is increased by using perforated pipes to transport the gas or the “waste
material” after burning oil/gas. There are also special “CO2 cannons” on the market. When
using organic material (i.e. manure), CO2 will come free automatically. The optimal level
of CO2 averages between 600 and 800 PPM. The maximum level is approximately 900
PPM, but some cultivars already show negative side effects at 500 PPM. Some negative
side effects are curling of the leaves and flowers and yellow coloring of the young leaves.
Be careful for the production of CO and ethylene with incomplete burning. By using a CO2
measuring device in the main pipe, the CO2 levels can be monitored. At levels lower than
340 PPM, the growth of the crop will slow down.
4.5 Humidity
The relative humidity (RV) determines how much a plant can evaporate. The optimal
humidity is somewhere between 70 and 85%. With a higher humidity, fungus problems
arise such as Botrytis and Sclerotinia. A high humidity level can be prevented by ventilation
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and heating to transport the moisture. Vents can be used to improve air circulation and
create a better microclimate. With a low humidity level, the temperature can be lowered,
ventilation reduced or moisture can be created by misting. A symptom of too low humidity
might be burning effects, because the plant can’t absorb enough water. Try to keep the
relative humidity above 50%.
4.6 Shading/White wash
When shading use shade cloth with a 40% blocking percentage. Retractable shade cloth
is needed to be able to use all the available light on darker days.
White washing the roof is another option. Whitewashing is especially recommended in
periods of warm weather. White wash will contribute to a more moderate climate in the
Greenhouse. The disadvantage with white washing is that you won’t be able to use all the
available light on darker days. Both shading and white wash contribute to longer
stemlength, which in certain circumstances can be more important than production
numbers.
There are several different options for shade cloth. Black shade cloth, white shade cloth
or a combination of energy and shade cloth. Important characteristics are to have
approximately 40% blockin percentage and to use a system that can be retractable. A
retractable system has the benefit that all the available light can be used on darker days.
5. HARVESTING AND PACKAGING
Correct picking of the flowers is very important for the vase life of the picked flowers.
Flowers that are harvested too soon or too late will have a shorter vase life. The optimum
picking stage is when the flower has developed two or three rings of mature stamens. For
semi and double varieties these two rings can’t always be seen. In this case you should
check the position of the flower head (horizontal) and the stability of the stem underneath
the flower head.
5.1 Picking
Picking is done by pulling or bending the stem to the side. It is important to find the natural
breaking point at the base of the plant. When done correctly the entire stems are pulled or
bent out of the base of the plant. Especially with younger plants and certain cultivars, it is
necessary to do this carefully to prevent pulling the shoots from the plant. After “picking”
the flowers are put in bunches (10, 12 or 20 stems) and taken to the main path. Be careful
not to handle to many flowers at once since the petals are vulnerable. Then the flowers
need to be put in water (with some bleach) as soon as possible. Before putting them in
water, cut the heel of the stems so the absorption of water is easier. Approximately 1 inch
of the bottom part of the heel of the stem (usually hairy and reddish).
5.2 Internal Transportation
It is Important to work with clean materials in a clean environment. Bacteria growth has a
very big influence on the vase life. Chlorine will prevent the bacteria growth on the stem.
Put the right amount of chlorine (too much will lead to bleach problems on the stem, too
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little bleach won’t have an effect on the bacteria growth). It is not necessary to add a food
solution (sugars) to the water.
Time Period
7% CI
10% CI
15% CI
Buckets/Cars 100 PPM
< 4 hours
1.4 mI/I
1.0 mI/I
0.7 mI/I
Transportation 25 PPM
> 4 hours
0.36 mI/I
0.25 mI/I
0.17 mI/I
Dose chlorine solution in water with different % of chlorine
Important tips:
Clean the buckets and carts at least once a week thoroughly. The amount of water in the
buckets should be relatively low. It is sufficient when approximately 10 cm of the bottom
part of the stems stand or hang in the water.
5.3 Grading and Packing
After picking, the flowers are graded according to quality, stage of maturity, flower diameter
and stem length. There are several different methods to pack the Gerberas. The most
important thing with packing is that the sensitive and vulnerable flower head is protected
during transport. The flowers damage easily, which is visible to the customer. Different
ways of packing are: Carton boxes, plastic cups, plastic netting or plastic covers. There are
several new methods in the market, which are combinations of the above. One of them is
the Gerbera Flower racket, which can be bought exclusively with Terra Nigra. Try to keep
the transport time to the customer as short as possible. When necessary, the flowers can
be stored in a cooling room. The optimum temperature is 8ºC. With lower temperatures
the color and quality of the flowers are decreased. Botrytis might occur with a high humidity
in the cooler or with large variances in temperature.
5.4 Handling by the Consumer
When the product arrives at the consumer it should be removed from the packing, ½” –
1” of the stem should be cut and be put in clean water with some bleach (1tbsp/gal water).
Change the water every 2 to 3 days and cut the bottom part of the flowers again. Avoid
direct sunlight, extreme temperatures and draft. Gerberas have many eye-catching colors
and as a result can be mixed in many bouquets.
6. PEST CONTROL AND DISEASE PREVENTION
6.1 General
Protection of the crop is of major importance when growing gerbera plants. First, focus on
prevention so disease, insects, and weeds don’t have the chance to develop. Hygiene in
your company should be your top priority as well as a requirement. The use of chemicals
should be your last resort. Many solutions are extremely poisonous and should be handled
with care. In addition, each treatment with such solutions will have a negative effect on
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the growth and production of the plants. Try to keep the usage of chemicals at a minimum.
Always rotate different products to prevent resistance. Depending on the cultivars, some
solutions will damage the flower or crop. When in doubt, always experiment with a smaller
area first. Integrated Pest Management control in Gerbera is feasible. The combination of
biological products, natural predators and insect growth regulator (IGR chemicals) has had
a lot of success in the last years.
Because legalities differ per country, no details will be given regarding the available and
allowable brands. However, a short description of the diseases and pests will be given in
the following section.
6.2 Insects
Leaf miners (Liriomyza)
First signs of leaf miners are little white spots on the leaves that develop into tunnels at a
later stage. The larvae are light yellow. The mature flies are easily recognizable because of
a yellow mark on top of their head. There are several natural enemies commercially
available of which Diglyphus isaea has been very successful.
White fly (Trialeurodus)
White fly pollute the crop and flower with their secretions. Because of their secretions of
the sweet substance honeydew, a fungus develops on the leaves that slows down
assimilation. The flies are white and usually clearly visible underneath the leaves. That’s
the place where you also can find the larvae and eggs. Because of its fast cycle with high
temperature, fast action should be taken. Different parasitic wasps and predatory bugs
are commercially available. In the IPM programs white fly is the most difficult pest to
control.
Thrips (Trips, Franklieniella)
Many different type of thrips exist. Visible damage done to the ray flowers are small brown
and white stripes and malformed flowers. With serious problems, shiny silver colored spots
can be found on the leaves. Thrips usually live in the flowers and are very small. Shaking
the flower head will cause the thrips to come out. They are carriers of viruses. Predatory
mites and bugs are commercially available.
Aphids (Aphidoidea)
Miscellaneous types of aphids exist. They pollute the crop and cause malformation.
Parasitic wasps and other natural enemies are commercially available.
Mites (Phytonemus, Throphagus)
Many types of mites can cause damage to your crop. Often, the flower heads are
malformed partially and the foliage is smaller, shiny and curly. Flowers also have a different
color. Before choosing the chemical, find out which type of mite is attacking your crop.
Mites can’t be seen with the naked eye. Well-known mites are cyclamen mite, Luis mite
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and Brevipalups. Natural enemies are not commercially available. Mites like these often
form a negative side effect of an IPM program.
Spider Mite
White and dull spots on the leaves, with more serious problems webs will be visible. The
little spiders are located underneath the leaves and suck on them. Spiders thrive in a warm
and dry environment. Predatory mites are commercially available of which Phytoseiulus
persimilis has been very successful.
Caterpillars (o.a. Spodopter)
Caterpillar damage to the crop can accelerate quickly. They will eat holes in the leaves and
sometimes leave the epidermis intact. In addition, the flowers are eaten in the heart of
leaves. The Florida moth (Spodoptera) is the most feared. The moth is gray/brown and the
caterpillar is green with a yellow stripe. The miscellaneous types of caterpillars and moths
are difficult to distinguish. The moths should be caught with lamps and “stick paper”. In
an IPM program the Bacclious thuringiensis (all types) are used very successfully.
Snails (Mollusca)
Small snails attack not only the young leaves but also the buds in the heart of the plant.
Often slime traces are visible on the leaves. Snails’ grains are usually an effective manner
to solve the problem.
Mice
The flower buds are partially or totally eaten. Often you can find some traces around the
plants. A mice plague can eat your entire production. Hygiene in and around the
greenhouse is of major importance. In addition, you can use traps, cats or poison.
Nematodes (Melidogyne)
The plants often show a slow down in growth at certain spots. The roots have small, glazed
lumps in which the nematodes are located. In a later stage, the roots will show signs of
rotting. Before planting a new crop. It is very important to sterilize and prepare the soil
thoroughly and buy quality plant material. Treatment of certain spots is possible with
miscellaneous chemicals.
6.3 Diseases
Plants become diseased when attacked by certain fungi, bacteria, viruses or nematodes,
when environmental conditions are favorable for disease development, and when the
plant is susceptible due to age or genetic make-up. Most microorganisms don not cause
plant diseases, but are in fact beneficial because they recycle nutrients by breaking down
dead organic matter to increase its availability to plants. An integrated disease control
strategy focuses on preventing the introduction of disease causing microorganisms
(pathogens), managing the environment to promote healthy plant growth, using resistant
cultivars, monitoring for early signs of disease, practicing good sanitation and early
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correctly identifying problems. The following table gives a simple key to diagnosis of a
disease.
Table 6.1 General key to disease diagnosis:
Overall

Damping-off
Stunting of plants:







Pythium, Phytophtora, Rhizoctonia or
Thielaviopsis root rot
over or under watering
bacterial soft rot
insects feeding on roots
low fertility
nematodes
high salts and/or improper pH
Wilting, dieback





poor root growth, root rot (Pythium,
Phytophtora, Rhizoctonia)
Xanthomonas blight
Verticilium
Fusarium
Tomato spotted wilt virus (TSWV) or
impatiens necrotic spot virus (INSV))
StemsStem rot



Sclerotinia
Botrytis
TSWV
Black areas


TSWV
Chlorine damage
Girdling of stem at crown

Rhizoctonia
Leaves/Flowers
Chlorosis
 Poor root growth (check for root rot)
 Low pH; nutrient deficiency
Leaf reddening
 Poor root growth
 Low nutrition levels
 Cold temperatures
Red blotches
 Downy mildew
Raised corky spots
 Oedema caused by a saturated media and high
relative humidity
Leaf spots
 Botrytis, Alternaia, Xanthomonas or Pseudomonas.
 TSWV
 Miscellaneous fungi and protists
White, powdery growth
 powdery mildew (do not confuse with spray residues
or white ash)
Small spots on petals
 Botrytis, miscellaneous fungal blights
6.4 Parasites
Botrytis
On dead and wet leaves, a gray-brown fungus will develop. Infection usually occurs on
wounds. Because the flowers are so vulnerable they can be attacked without having any
wounds. This is called spotting. The disk florets show small gray/brown strips that will start
rotting. Botrytis occurs only with high humidity (N93%). Preventive measure can be taken
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by lowering the RV (ventilate, heat, and air circulation) and gradually increase when heating
the greenhouse (a maximum of 1 ºC per hour). Hygiene is also important.
Powdery Mildew (Oidium)
White, powdery spots occur on the upper side of the leaves. It is easy to rub the spots of
the leaves. These spots can turn brown or yellow in a later stage. Usually this fungus occurs
with a high humidity or draft. However, it is also possible for this fungus to thrive in a drier
environment. Use sulfur as a preventive method against this problem.
Sclerotinia Dusting Sulfur (Sclerotinia)
White, hairy fungus will develop. In this white and black material sclerotinia will form. These
are round, similar to rat droppings, funguses which can be found in the heart of the plant.
The parts of the plant above the attacked spots will wilt and rot. Preventive measures that
can be taken are thorough soil sterilization, good plant material and avoidance of a too
high humidity.
Phythium
The roots color brown, the top layer of the roots will loosen, and the plants start wilting.
Phythium is a clear “weakening parasite”. Good sterilization and plant material, control
large variances in temperature, control of irrigation/drainage and healthy plants are
preventive measures that can be taken. Take plants with phythium out of the soil and treat
the spots several times with chemicals.
Phytophtora
Signs are difficult to differ from Phythium. Plants are wilting fast and the base is rotting
while the roots can look healthy longer. Phytophtora is very aggressive and also attacks
healthy plants. For preventive measures, see Phythium.
Fusarium
Often, the shoots and plants die from the base of the plant. Sometimes, red spores are
visible. The vascular bundles usually rot from within.
6.5 Other disorders
Viruses
The most known is the Tomato Mosaic virus. Often the leaves show yellow, concentrated
circles that become necrotic. Another symptom is the necroses starting in the veins. The
veins usually grow crooked and the leaves are malformed. The flowers also change color
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and are malformed. There are no treatments against viruses. Take attacked plants out
immediately and treat for hosts of the virus. (i.e. Thrips).
Winter flowers
Flowers grow crooked and have poor developed central flowers. The flowers grow and
develop more slowly and sometimes are aborted. Winter flowers develop during periods
with a lower light intensity. Because of the lack of light (often combined with higher
temperatures), not enough assimilation occurs for the growth and development of the
buds.
Sugar rot
This mainly happens when growing in substrate and is not yet seen when growing in soil.
The symptoms are “fermenting heads” in the center of the plant that causes a typical
sweet/sour smell. Geotrichum and bacteria cause a yeasting of sugars. Often red fruit flies
can be seen. The heart of the plant can rot entirely. It is still not known if or which bacteria
causes sugar rot or which treatments can be applied. Keeping the plants healthy, control
of irrigation/drainage and temperature seems to prevent it from occurring in the crop. Use
treatment against the fruit flies and use fungicides.
Stem breakage
The stems of the flowers are very hard and show crack. Sometimes the flower head breaks
off when touching it. Because of too much root pressure and/or too little evaporation, the
tension in the cells increases too much and causes breakage. Preventive measures that
can be taken are: lower the RV, lower the root temperature, or change the fertilizing
schedule (EC of certain elements).
Wilting stems
The stems are often very long, stretched and wilted. This can be caused by many factors.
It can be too dark or the flowers can’t absorb enough water. Often wrong fertilization is the
cause. In the winter it might be caused by a deficiency of Ca (in the cell wall). A lack of K
(potassium) might be another factor resulting in too low pressure in the cell.
HYDROPONICS
1. General
Growing in hydroponic systems is getting more popular. The reason being that many soils
today do not match the two most important demands for growing medium: the percentage
of oxygen around the roots (optimum is 30%) and a good vertical drainage. Because the
inputs are better controlled the results of the culture (production and quality) can also be
improved when growing on hydroponics. However hydroponic culture is not an automatic
guarantee of better results. It requires more attention and know how from the grower and
more advanced technical installations. The water supply is very important; a substrate unit
with pH and EC control is needed to regulate the amount of water and the nutrition solution
given.
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2. Substrates
Hydroponic culture takes place in different systems with different kinds of substrates all
over the world. Mixtures of different materials are mostly used, many of which can be found
locally.
There are many different substrates. Some of the substrates used today are described
below.
Peat
Peat is the most commonly used substrate. There are many different types of peat,
depending on the particular history of the area and the age of the peat. Many times the
young, blond, fibrous peat is used, as it has better characteristics than the old, black, fine
peat, which often stays too wet. Also a combination of different types of peat is used,
eventually mixed with materials like perlite or rice chaff. Before culture, the peat-mixtures
are often amended with fertilizers like Dolokal or NPK-mixes, depending on the results of
the analysis.
Cocopeat
During the last years this substrate has become more important, mainly in cultures like
Roses and Carnations, but also in Gerberas. There are two types of Cocopeat: dust, bits
and fiber of which dust is still the most common. It is very important to know the origin of
the Cocopeat. There are many different qualities on the market; never use Cocopeat that
is found close to the sea as the EC is much too high. Cocopeat retains a lot of water but
still contains a good amount of air. But it can also remain too wet during culture; you can
control this by giving only a few but longer water-turns per day. Often Cocopeat is mixed
with other materials like Perlite to improve the airiness. In general the crop has a more
vegetative growth compared with the culture in soil or organic substrates. Because
Cocopeat binds a lot of Calcium it is very important to add extra Calcium in the beginning
of the culture.
Perlite
This material can be used as a 100% substrate or mixed with other materials to increase
the air-ratio. In the South of Europe the culture in only Perlite is common. Perlite can also
be disinfected after culture and used again, but due to the existence of dirt absorption the
water and fertilizer will increase. By nature, perlite has a high pH; during culture you can
give water with a relatively low pH-level. The ratio of air in this substrate is very high; perlite
is inert, lightweight and has almost no buffer. There exist different sizes of the perlite-grain;
mostly used is the bigger size of 3-6 mm.
Clay grains
The bigger clay-grains (0.5-1 cm) are mostly used when growing in pots, to create a layer
of drainage at the bottom of the pot. Before planting they put about 4 cm of clay-grains
inside the pot and then fill it up with the rest of the substrate. In this way the excess water
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will always be able to leave the pot, even after a long culture when the substrate is
becoming more compact.
Rice-chaff
This material is used a lot to improve the structure of the substrate. It is mixed with peat
or Cocopeat to keep the air-ratio high enough. The percentage used is depending on the
existing structure of the substrate and lies between 20 and 50%. Be sure to use the cooked
rice-chaff that is completely sterilized and free of strong chemicals, which are sometimes
used in the culture of rice.
Bark
Bark of different types of trees is also used sometimes as a substrate or part of a mixture.
Mostly the softwood is used, which has already been composted for some years. If you use
bark of different types of pines, take note that many times there is resin inside which might
have effect on the culture. Hard bark of strong trees is sometimes used as the lowest layer
of the substrate to have a good and free drainage.
Pine-needles
The well-composted needles of different types of pines or conifers are used on occasion.
Many times the pH of this material is very low and after a while in the culture, it loses its
structure. However it is sometimes mixed with other substrates.
Lava-stones
The rough lava material can be broken and filtered and after some preparations be used
as a substrate. It will always keep the same structure and to a low degree it also absorbs
some elements when fertilizing. It is also used to improve the structure of soil or in the mix
of different materials. The disadvantage is that the Gerbera roots cannot freely develop
when there are hard stones, which might cause problems in culture.
Sand
Pure sand is a perfect growing medium for Gerbera when growing in soil. When you grow
in pots, bags or containers (low volumes) it is less useful as a sole substrate. Because pure
sand has water drainage of almost 100%, it is difficult to use. It is sometimes used in a
mixture.
Clay
Clay is mixed sometimes in small percentages (5-10%) to improve the chemical buffer of
the substrate. As clay is absorbing and releasing water and nutrients, it gives more buffer
to the substrate. On the other hand it makes it more difficult to control the culture. Do not
use too much clay because the mixture becomes too wet, which might cause problems.
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Rockwool
Rockwool is used a lot as a growing medium in Northern Europe. This fiber product arises
from stones that have been melted at a high temperature. When cooling the fiber structure,
it can be made into slabs, blocks or granulate. Rockwool is inert and has almost no buffer.
This makes it easy to control the culture, but on the other hand, makes it more
complicated. It requires the perfect technical installations and irrigation system. Mostly
Gerberas are grown on the rockwool mats, on which the blocks with the plant are planted.
For the culture in pots or containers, a new type of rockwool is developed: the cubes. This
is a granulate with cubes of rockwool with the size of approximately 1 cm x 1 cm. This
granulate in culture contains even more air than the slabs of rockwool. On the other hand
you have to give water more precisely and frequently. Not very often is rockwool used in a
substrate mixture.
To compose the substrate that is best suitable for your situation you can keep the following
points in mind:

The optimum air:water:substrate rates for the medium is 1:1:1;

The substrate must be well-aired as well in the beginning as during the whole culture;
the structure must remain the same during a minimum of 2 years;

The substrate must absorb and release water easily;

There must be free vertical drainage

In case you use organic material use only composed material;

The substrate must hold the plants securely;

The substrate must be completely sterile

It is recommended to make a chemical analysis of your substrate before planting to
calculate the exact amounts of fertilizers that are needed during growing
3. Drain water Analysis
For Hydroponic cultures the following target figures apply:
Ranges drain water gerbera macro elements (milimol/liter)
Value
PH
EC
N
P
K
Mg
Ca
S
Na
CI
Low
5.0
1.5
0.1
0.7
5
1.0
4.0
1.5
0
0
High
6.0
3.0
0.5
1.3
9
3.0
7.5
3.5
LOW
LOW
Target
5.2
2.2
<0.5
1.0
6
2.0
5.0
2.5
LOW
LOW
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Ranges drain water gerbera microelements (micromol/liter)
Value
Fe
Mn
Zn
B
Cu
Mo
Low
30
1
3
35
0.5
0.2
High
60
4
7
60
2.5
2.0
Target
40
3
5
40
1.0
0.5
Based on your water and substrate analysis Terra Nigra can provide you with a special
recipe to reach the target values.
4. Planting methods
The most used system at the moment is a pot system were the pots are placed in a two row hanging
system with free flowing drainage. For free flowing drainage it is important to have no contact
between pot and gutter/table and that the pot has sufficient holes. The pots are 19 cm high (3.6
liters) and filled with one of the above-mentioned mixes. Irrigation is done with one spaghetti
dripper per plant and the pH and EC are computer regulated. Recirculation using the drain water
is possible.
Planting
Before planting, it is necessary to fill the pots with the substrate and approximately 5-cm
of material to improve drainage of the bucket. Start by putting the material such as clay
petals or pebbles on the bottom of the bucket (approximately 750-ml). Then fill the pot
with the substrate mixture. Because the substrate will compress, it is recommended to fill
the pots with an extra cap of approximately 2-cm. Insert one dripper per bucket and start
watering a few days before planting to flush the growing medium (25% drain).
When planting the jiffy in the bucket, leave the top part of the jiffy (approximately 1-cm)
above the growing medium, because the plant will be pulled down during growing. Place
the dripper against the jiffy immediately after planting.
Planting systems
When planting in pots there are several ways of making a construction to get the specifics
mentioned above. The following diagram gives you an idea of the dimensions that can be
used.
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Hydroponics pot system:
You can use wooden frames, rebar etc. or buy the whole system ready made. Your set up
has to be in such a way that you will get about 6.5 plants per m2.
Irrigation
During the first few weeks it is best to water carefully: the drain percentage should be 0 to
10%. Measure the drain of approximately 5 plants daily to check the percentage. If the
percentage is too high, decrease the cc per irrigation time. Give approximately 5 irrigation
periods of 50 cc with a pH of 5.5 and an EC of 1.5 to 2.0.
After two weeks, when the plants have developed new roots, the drain should be about
10%. At this moment the dripper has to be moved towards the edge of the pot (in between
the jiffy and the side of the bucket). After about four weeks, when the plants have
developed a good root system, the drain percentage can be increased to 15%. When the
first flowers show, this can again be increased to 25%. This increase can be accomplished
by increasing the cc to 100cc per watering period. If this does not create a sufficient
increase, it might be necessary to increase the number of irrigation periods. Check the
drainage daily and adjust it when necessary. Start your first water cycle early in the morning
(about 1 hour after sunrise) and your last cycle about 5 hours before sunset. This to let the
substrate dry of at the end of the day so the first cycle doesn’t give any drain. Leave about
60-90 minutes in between cycles. Your daily drain should be around 25%.
There are some characteristic differences between the different substrates. In general
rockwool substrates need more irrigation periods (50% more). Coco substrates need
longer periods (up to 150 cc) but lesser periods a day. It is recommended to stop 6 hours
before sunset.
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During cultivation it is important to keep the pH of your irrigation water at 5.5 and your EC
between 1.5 and 2.0. It is recommended to flush your substrate (by giving about 1000 cc
clean water with low EC (0 preferably) to prevent building up of salts. This has to be done
at least ones every two months.
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