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Cut Roses
Horticulture 429
Floriculture Crop Production
Dr. Terri Starman
Introduction
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Rosa L. hybrids
100 genera
2000 species
Rosa genera are woody
Production has shifted to areas near the
equator
• High light and cool temperatures
Rose Morphology
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Woody
Thorns
Upright, trailing, or climbing
5 petals
Fruit is called a hip
Flowers are white, pink, yellow, orange or
red and blends
• Powdery mildew, blackspot and Botrytis
Rose Propagation
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Seed for breeding
Bud grafting for cut flowers
R. X noisettiana is used for rootstock
Stenting is a form of grafting that is
replacing bud grafting
Stenting
• Seedlings rootstocks of R. chinensis
• Single leaf bud scion is placed into a
downward cut
• Held with a small clothspin
• Union occurs within 3 weeks
• Under fog, mist or in high humidity
• 750F (240C)
Flowering Control and Dormancy
• Day neutral
• Flowering is recurrent, year-round
• Flower initiation is not dependent on
environment
• Floral differentiation occurs shortly after axillary
buds are released from apical dominance
• Transition from vegetative to reproductive occurs
in 4 to 21 days, when axillary shoots are 1.25 to
1.50 inches long
Flowering, cont.
• Axillary buds from the upper nodes form
flower buds sooner and with fewer leaves
than lower nodes
• The speed and quality of a subsequent cut
flower crop are dependent on the nodes
remaining after the flower is harvested
• Irradiance, temperature and available CO2
influence growth and development of
roses in greenhouses
Temperature
• Development increases as temperature
increases including the rate of axillary bud
break, shoot development, leaf unfolding,
& flowering
• Excessively high or low temperatures
increase number of blind shoots
• 60-620F night, 64-720F cloudy day, 750F
sunny day
Light and Water
• Light is very important and supplemental
light is used in northern latitudes
• 8 to 24 hours/day
• 300 – 1000 fc
• Good quality water
• Perimeter bench watering
• Constant flow tray systems grown in rock
wool blocks or coir dust, water is
recirculated
Nutrition
• 1500 ppm CO2
• Routine media and tissue testing are
necessary
• Organics used in traditional beds
• Liquid application
• 150-200 ppm N
• Nitrate: Ammonium is 5:1 in summer and
10:1 in winter
Media, Spacing and Support
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Soil, amended and mulched
pH 5.5 to 6.0
Newer production systems are hydroponic
1 to 1.4 ft2 / plant
Three rows across a bed
Three layers of wire with openings 6 X 6
inch or 6 X 8 inch
Pinching and Pruning
1. To remove broken roots or shoots and reduce
cane height at planting. Prior to planting,
broken roots and shoots are removed and
cane height reduced leaving 3-4 dormant
axillary buds.
2. Once planted and new shoots begin to
elongate, flower buds are removed at either
one of two stages of growth. If a soft pinch
then 2X.
a. Soft pinch- flower buds smaller than a pea
b. Hard pinch- flower buds larger than a pea
Pinching and Pruning
3. To harvest flowers – leave 1, 2, or 3
nodes or cut below the “knuckle” i.e.
junction of axillary shoot and stem from
which it is growing. Below the knuckle is
used if height reduction is desired. Above
the knuckle is used to control the rate
and number of return shoots. Leaving
less nodes = slower growth, longer
stems, and more leaves.
Pinching and Pruning
4. Five to 8 weeks prior to a major holiday,
depending on cv., to ensure a large
number of flowers available for a holiday,
sacrifice flowering shoots by pinching to
produce more flowers at the same time.
5. After Mother’s Day into late June plants
are severely cut back to a height of 2-3
feet to rejuvenate old plants.
Scheduling and Timing
• Traditional method
– peak production for major holiday
– dependent on temperature, light & last pinch
and position of last cut
– 6-8 weeks
• Bending or Arching method
A visit to Rose Gene
Technology
Watsonville, CA
Formed in 1998 to focus on breeding
and production of roses for cut flowers.
They produce mini plants and one-year
old plants
Bending or Arching
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Production continues uninterrupted
Higher quality due to light penetration
Longer stems are produced
Increase stem thickness
Uniformity of stem length
Easier to harvest
Eliminates support wires
Harder to control spider mites
Insects and Diseases and
Physiological Disorders
• Spider mites, thrips, aphids, whiteflies,
caterpillars, shore flies, and fungus gnats
• Biological control of thrips and mites is
possible
• Mildew (Sphaerotheca) and Botrytis
• Environmental control of diseases
• Bullhead flowers i.e. flowers are not
tapered at the apex caused by too low
temp. or thrips and cultivar susceptibility
Diseases
Water condensation occurs when
temperatures fall below the dew point.
Guttation of water along the edges of
leaves also occurs. Drying must occur to
prevent disease establishment. Increase
the temperature 1.5 to 30F when the
relative humidity reaches 85-87% and
open the vents slightly. This will help
control mildew and Botrytis.