Download Greenhouse Production of Bedding Plant Snapdragons

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A u b u r n
U n i v e r s i t i e s
Greenhouse Production
of Bedding Plant
Snapdragons
S
napdragons (Antirrhinum majus) are enchanting
and delightful flowers that have been enjoyed for
centuries. These Mediterranean natives have many
pleasing attributes, from their delectable fragrance to
their full range of heights and colors. They are popular
as bedding and container plants and as cut flowers. The
upright flower shoots are covered with buds that open from
bottom to top, providing brilliant color for an extended
period of time. Snapdragons perform best in the landscape
in cool weather, and most cultivars can even tolerate a
light frost. They tend to suffer in the summer heat of the
southeastern United States, and, therefore, are typically
used as fall or early spring annuals. Snapdragons flower the
best in full sun and well-drained soil enriched with organic
matter. They range in size from 4 inches to 2 to 3 feet tall,
depending on the cultivar. Flower colors range from white
and yellow to orange, red, and purple to almost black. The
only color missing is true blue.
Cultivars
Snapdragons are classified by height into three
categories: dwarf, medium, and tall. Dwarf plants grow to
be 6 to 12 inches tall in a dense, bushy habitat and produce
abundant flower shoots. These cultivars commonly are used
in the landscape for border edging or in mixed containers.
In greenhouse production, they are grown in 36-cell market
packs or 4-inch pots. The medium-sized plants grow to be
12 to 24 inches tall and often are used as border fillers or as
cut flowers. In greenhouse production, they are grown in
36-cell market packs or 4-inch or larger pots. Tall cultivars
have a dominant, single flower shoot, grow to be 24 to 48
inches tall, and mostly are used as cut flowers, but also may
be used in the back of a border. These are not often grown
for bedding application.
There also are trailing types of snapdragons often
used in containers and hanging baskets. Some of the
best trailing snaps are the Luminaire series. An unusual
butterfly-type flower can be found in the Bell and La Bella
series in which the conventional floral tube is flared at the
end, giving the flower a more open appearance. Because
of the more recent introduction of dwarf and mediumsized plants, snapdragons have become more popular as
bedding and edging plants than their more traditional roles
of background and cut-flower plants. This publication will
focus on snapdragons commonly grown for greenhouse
production in either market flats or containers and used
primarily as bedding or flowering potted plants. Series and
cultivars of snapdragons for bedding plant and pot culture
are in Table 1.
Seed Propagation
Stage 1
Snapdragon seeds are very small but readily germinate
under proper conditions. Seeds should be sown in 406cell plug flats containing sterile germination media with
medium moisture content and a pH between 5.5 and 5.8.
A higher pH can cause iron deficiency in snapdragons.
The substrate temperature should be kept between 64
and 68 degrees F; temperatures higher than 75 degrees F
can delay germination. Because snapdragon seedlings are
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very sensitive to high soluble salts, electrical conductivity
(EC) should be less than 0.75 millimhos per centimeter
(2:1 extraction method), and ammonium levels should be
kept at less than 5 parts per million. Light is necessary for
germination of some cultivars; contact the seed supplier
for specific cultivar recommendations. Seeds of non-lightsensitive cultivars can be covered with a light layer of fine
vermiculite to maintain adequate moisture levels next to
the seed. Radicle emergence can be expected within 4 to
8 days after sowing; when they begin to emerge, reduce
moisture levels to encourage roots to penetrate the media,
which should be moist but not saturated.
Stage 2
After radicles emerge, remove flats from the seed
germination chamber, if used, and then reduce substrate
moisture level. Light levels should increase to 450 to
1,500 footcandles. Once a week, apply 50 to 75 parts per
million nitrogen using a 15-0-15 fertilizer or other low
ammonium fertilizer formulation. If possible, alternate
fertilizer with clear water. Maintain substrate temperatures
between 65 and 70 degrees F, and dry the foliage before
nightfall to prevent disease. Maintain water alkalinity at 60
to100 parts per million and ammonium levels at less than
10 parts per million. This stage requires 7 to 14 days.
Stage 3
Lower soil temperatures to 62 to 65 degrees F by night,
and raise light levels to 1,000 to 2,500 footcandles. Allow
flats to dry between irrigations, but avoid wilting. Increase
fertilizer to 100 to150 parts per million nitrogen weekly,
alternating between 20-10-20 and 14-0-14 formulations.
However, avoid ammonium-based fertilizer if growing
below 65 degrees F. During this stage, supplement fertility
with magnesium sulfate once or twice and occasionally
leach them with clear water to reduce EC. If stretching
might be a problem, apply A-Rest 3 to 4 weeks after sowing
at a rate of 10 parts per million. Fungicides can be applied
at the lowest recommended rate to control Pythium,
Rhizoctonia, and Thieleviopsis. This stage requires 14 to
21 days.
Trailing Cultivars
Trailing snapdragons, such as the Luminaire and
Playful series, are propagated vegetatively. The best trailing
cultivars are patented; therefore, propagation by unlicensed
propagators is illegal. Also, stock plants can carry a
number of latent diseases and should be virus-indexed
and maintained in a clean stock system. For these reasons,
growers should buy unrooted cuttings or rooted liners.
If unrooted cuttings cannot be planted immediately,
store them for no longer than 24 hours at 50 to 60 degrees
F. Stick cuttings in Oasis wedges or in a sterile medium
with a pH of 5.6 to 5.8. Media temperatures should be
maintained at 68 to 72 degrees F with an air temperature of
75 to 80 degrees F during the day and 68 to 70 degrees F
during the night. Light levels should be maintained at 500
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to 1,000 footcandles. Removable shade is an easy method
for adjusting light levels as cuttings mature. Use intermittent
mist to maintain humidity around cuttings; the frequency
should be adjusted based on light levels and temperatures.
Calluses should form in 5 to 7 days after sowing. Apply
a foliar fertilization of 50 to 75 parts per million nitrogen
using a 15-0-15 or similar fertilizer formulation as needed.
Cuttings are ready for root development once a
callus has formed and 50 percent of the cuttings have
differentiating root initials. Substrate and air temperatures
need to be maintained, and light levels should be increased
to 1,000 to 2,000 footcandles. Fertilizer also can be
increased to 100 to 150 parts per million nitrogen weekly
by alternating 20-10-20 with 15-0-15. Reduce the mist as
roots form; roots should develop 7 to 14 days after sowing.
Harden cuttings for 7 days before transplant or sale by
decreasing air temperatures to 75 to 80 F degrees during
the day and 62 to 28 degrees F at night, and increase
fertilization to twice weekly.
Growing On
The key to producing appealing, sturdy snapdragons
is cool temperatures. Plants may be exposed to light frost
if heat is unavailable, but the most economical crops are
produced at cool temperatures. Full sun and sufficient
ventilation will help keep stems strong, and plant height in
market packs can be controlled if water and fertilizer are
applied somewhat conservatively.
Transplant the seedlings when roots easily hold the
plug mass together and have two to three sets of true
leaves; do this in a timely manner to avoid stunting growth.
Bedding snapdragons perform best if transplanted to 18- or
36-cell flats and also do well in 4-inch pots or in groups of
three to five plants in a 1-gallon container. Trailing snaps
should be planted in 4-inch pots or in pairs in 6-inch pots.
Four to five cuttings can be planted in a 10-inch
hanging basket.
Choose a sterile media with a moderate initial fertilizer
rate and a pH of 5.5 to 6.2. Maintain high light levels
at 5,000 to 6,000 footcandles because low light causes
stretching, reduces flowering, and increases crop time.
Temperatures should be 72 to 75 degrees F during the
day and 62 to 65 degrees F at night. You may reduce night
temperatures to 45 to 50 degrees F once plants establish to
promote flowering. Once flowering begins, maintain night
temperatures below 60 degrees F.
Apply fertilizer twice weekly at 150 to 200 parts per
million nitrogen alternating between 20-10-20 and 15-0-15
formulations. Reduce this rate when flower shoots begin to
elongate to increase postharvest life. For trailing snaps, it
is important to maintain fertilizer levels because low levels
hinder plant branching.
Pinch trailing snaps once the roots reach the edge of
the container. Throughout the rest of production, shear
plants to maintain shape. Four-inch pots require one pinch;
6-inch pots, two pinches; and 10-inch hanging baskets, two
to three pinches. Also, pinch taller bedding snapdragons
planted in larger pots to promote branching and multiple
flower shoots.
Height control can be a problem in bedding plant
snapdragons grown from seed. When grown under
recommended cool temperatures and high light, growth
retardants should not be necessary. If needed, apply A-Rest
as a 10 to 26 parts per million spray or B-Nine as a 2,500
parts per million spray on snapdragon seedlings. Some
growers tank mix B-Nine and Cycocel with 800 to 1,000 of
each after transplanting. You also may use Bonzi as a 60 to
90 parts per million spray or Sumagic as a 25 to 50 parts per
million spray to control the height of snapdragons, but they
may delay flowering and can cause less uniform flowering.
Scheduling
Crop production time varies depending on cultivar.
In general, plug crop time from seed to transplant is 5 to
6 weeks. Dwarf types take 4 to 5 weeks from transplant
to finish in market packs and 5 to 6 weeks in 4-inch pots.
Medium-sized types take 10 to 12 weeks from transplant to
finish in 4-inch pots and 12 to 13 weeks in 6-inch pots.
Troubleshooting
High pH can cause stunted or uneven seedling growth
or poor root development. Also, very high pH can cause
boron deficiency. A high pH or a cool, wet substrate may
cause interveinal chlorosis of immature leaves, resulting
in reduced iron uptake. If the problem is high pH, spray
the plants with iron sulfate at 33 ounces per 100 gallons of
water. If the deficiency is caused by the cool, wet medium,
dry the substrate and increase the temperature. Symptoms
should diminish within 3 to 4 days.
Botrytis infection or chronically wet substrate can cause
the plant to collapse. High nitrogen concentration, applying
too much fertilizer under low light conditions, or low light
and overwatering can cause excessive foliage growth.
Foliage necrosis can be caused by high EC or by the plant
drying out between irrigations. Trailing snapdragons that do
not branch properly may not be receiving enough light or
were not properly fertilized during early growth stages.
Pests and Diseases
Snapdragons have fewer problems than many other
bedding plant crops. Fungus gnats and shore fly larvae are
the most common insects on seedlings. Aphids, mites, and
thrips may injure mature plants. Be careful when applying
pesticides to snapdragons because some are known to
cause damage to flowers; carefully read the label to
avoid problems.
Downy mildew, powdery mildew, Pythium, botrytis,
rust, Phyllosticta blight, and Anthracnose are common
fungal diseases on snapdragons. Tomato spotted wilt virus
and impatiens necrotic spot virus also can be problems
on vegetatively propagated snapdragons. To help control
foliar diseases, avoid wetting foliage. If overhead irrigation
must be used, water early in the day to allow foliage to dry
before nightfall.
Greenhouse Production of Bedding Plant Snapdragons
Table 1. Series and Cultivars of Snapdragons for Bedding Plant and Pot Culture in Greenhouse Production1
Series / cultivar2
Company source
Garden
height
(inches)
Comments
Bells Series
Goldsmith Seeds
8 to 10
9 colors; butterfly-type flower; flowers
longer in garden; strong, well-branched
plants
Chimes Series
Goldsmith Seeds
6 to 8
10 colors; full, bushy plants loaded with
fragrant, colorful shoots
Coronette Series
S&G Flowers
20 to 24
9 colors; filler in garden or cut flower;
withstand wind and rain
Crown Series
S&G Flowers
16 to 18
14 colors; fast branching; strong garden
performance; mid‑height color in the
landscape
‘Floral Carpet Mix’
Benary Seeds
8
16 inches wide; very uniform; free
flowering; ideal for group plantings
‘Floral Showers Mix’
Benary Seeds
6
Wide, flat cushions; extremely early for
flowering sales
‘Frosted Flames Mix’
Harris Seeds
12
Open pollinated mix; bright, rich colors;
unusual white variegated leaves
Freesong Series
Bodger Seeds
14 to 18
12 colors; recommended for garden
beds, cut flowers, and 4-inch pot
production
Kim Series
Floranova
10 to 12
11 colors; branching habit; side shoots
and flower with central shoot; for pots
and landscape
La Bella Series
Goldsmith Seeds
18 to 22
6 colors; open butterfly-type flowers on
strong, well-branched plants
Liberty Classic Series
S&G Flowers
20 to 24
8 colors; sturdy flower shoots and
uniform habit
Luminaire Series
(cutting)
Ball FloraPlant
trailing
6 colors; free‑flowering, trailing plants
for containers and baskets
‘Magic Carpet Mix’
Bodger Seeds
6 to 8
Compact non‑hybrid mixture
Montego Series
S&G FLowers
8 to 10
14 colors; early flowering dwarf; strong
basal branching for a robust-like plant
Alabama Cooperative Extension System
1
2
Palette Series
American Takii
6 to 8
11 colors; uniform; early flower; wellbranched
Playful Series
(cutting)
Ball FloraPlant
6 to 8
6 colors; well‑suited to pot‑tight 4‑inch
programs
‘Princess White with
Purple Eye’
American Takii
10 to 12
Striking bicolor flower; uniform
flowering
Snappy Series
Hemgenetics
6 to 8
6 colors; very uniform flower time across
color range
Snapshot Series
Ball Seed Co.
6 to 10
11 colors; bushy, compact plants with
closely spaced flower on shoots
Solstice Series
Ball Seed Co.
16 to 20
9 colors; quick-finish; flowers 30 to 60
days earlier under short days than other
intermediate size, winter-flowering
cultivars
Sonnet Series
Sakata Seeds
12
10 colors; strong root system; sturdy
branches; can take high winds without
lodging
Tahiti Series
S&G Flowers
8 to 10
14 colors; dwarf plant habit; flats and
pots
This table is not exhaustive but includes series and cultivars widely available on the U.S. market.
Names enclosed in single quotes are single cultivars. Names without quotes are series of cultivars.
Table 2. Recommendations for Tissue Analysis Nutrient Levels in Snapdragon
Percent
N
P
K
Ca
Mg
S
3.80
0.30 to 0.50
2.00 to 3.00
1.00 to 1.50
0.84
0.46
Parts per million
Fe
Mn
75
139
Adapted from Mills and Jones, 1996.
Zn
Cu
Mo
B
56
9
0.85
30
Rachel Creel, Graduate Associate, and J. Raymond Kessler, Assistant Professor, both at
Auburn University
For more information, call your county Extension office. Look in your telephone directory under
your county’s name to find the number.
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