Hot New Cuts for a Cool Greenhouse

August 8, 2003 - 07:59

North Carolina State University research identifies cut flowers that grow better in a cool greenhouse.

In our never-ending search for new cuts, we have been working
with three species that have great potential for cool temperature greenhouses.
Linaria Lace produces tall open spikes of small rose, violet, white or yellow
snapdragon-like flowers. Lupine 'Sunrise' has spikes of mildly fragrant, blue
flowers with some yellow and white. Poppy 'Meadow Pastels' and 'Temptress'
produces 2- to 6-inch wide flowers in a broad range of knock-your-socks-off
colors including white, orange, yellow, salmon, rose and pink. Compared with
Meadow Pastels, Temptress has longer, thicker stems, longer postharvest life
and slightly stronger colors. However, Meadow Pastels is generally much easier
to germinate and has a higher germination percentage than Temptress. Some
growers have had few problems germinating Temptress while many others have had
little success. In fact, germination problems led us to use Meadow Pastels for
the production studies instead of Temptress.

Our goal for the production experiments was to develop
economical production protocols, examining production temperature, transplant
age and supplemental lighting of the plugs. The postharvest work determined
ethylene sensitivity, optimum cold storage duration, pretreatments and pulses,
vase solutions and substrates, and commercial preservatives for linaria and


Linaria 'Lace Violet', lupine Sunrise and poppy Meadow
Pastels seeds were directly sown into 105 plug flats using a peat-based
commercial media and germinated at 60° F. One half of the plants received
ambient light plus eight-hours of HID supplemental lighting, and the other half
of the plants were placed under ambient light. Average light levels were 2,145
foot-candles for ambient light and 2,700 foot-candles for HID supplemental
lighting, measured daily at noon. Seedlings were transplanted at the appearance
of 2-3, 5-6 or 8-9 true leaves. Linaria and poppy seedlings were placed at 41,
50 or 59° F night temperatures in the North Carolina State University
Phytotron, and lupine seedlings were placed at 59, 64 or 69° F night
temperatures in a polyethylene covered-greenhouse. Day temperatures were
10-17° F higher than night temperatures. Linaria seedlings were
transplanted into 4-inch pots spaced pot to pot, and lupine and poppy seedlings
were transplanted into 6-inch pots spaced pot to pot initially. The poppies
were later spaced to 9-inch centers. We used pots for the experiments because
we had to move the plants. However, all three species can be easily grown in
beds. Plants were irrigated with 150 ppm nitrogen from a premixed commercial
20-10-20 fertilizer during the week and with clear water on the weekends.

Data collected at harvest time includes stem length, stem
diameter (measured 2 inches from the base) and harvest date. We also estimated
profit/loss for each treatment, which factored in the amount of time in the
flat, time in the production area and sales price per stem. Linaria and lupine
flowers were harvested when 1/4-1/3 of the florets had reflexed petals. Poppy
flowers were harvested when the calyx cracked and petal color was visible.

Linaria. Linaria
proved to be an excellent flower producer, with each plant producing from
4.2-10.0 cut stems. Optimum production temperature was 50° F. Flowers
produced in 59° F were unmarketable, while 41° F production
temperatures produced longer and thicker stems, though production time was
greatly increased. Do not grow this plant warm or the stems will be thin, short
and completely unusable. In our work, the first plants to flower were growing
at 59° F, and we thought we had a dud on our hands. However, we completely
changed our minds when the plants in the 50 and 41° F treatments flowered.
The stems were tall, over 3 feet in some cases, thick and beautifully colored.

At 50° F, seedlings should be transplanted at the 2-3
leaf stage to maximize stem number, length and profitability, which was
estimated at $4.74 per plant. The close spacing allows for many harvestable
stems to be produced in a small area. Problems included thrips and root rot on
a few plants. Note that when transplanting, the seedlings form branches very
low on the plant, which can appear to be separate seedlings.

Lupine. The optimum
temperature was 59° F, which resulted in the shortest crop time, longest
stems and highest profitability of $0.76-0.88 per plant. Lower production
temperatures should be tried, as the optimum production temperature may
actually be lower than 59° F. Warm production temperatures above 64° F
should be avoided, as some of the florets aborted. Seedlings should be
transplanted at the 2-3 leaf stage under 59° F to obtain the longest,
thickest stems; however, profitability was higher for plants transplanted at
the 8-9 leaf stage due to longer time in the plug flat. Supplemental HID
lighting is not recommended, as it delayed flowering and did not increase
profitability. While thrips were a problem, lupine had few other insects or
disease problems.

Poppy. Poppy was
also an excellent flower producer, with each plant producing from 3.1-6.6 cut
stems in the experiment and up to 12 stems per plant in later work. The
59º F temperature was optimal, as it produced the longest stems in the
shortest time. At that temperature, plants should be transplanted at the 2-3
leaf stage. Supplemental HID lighting had a negligible effect and did not
influence profitability, which averaged $0.99 per plant.

Poppies suffered from powdery mildew, which not only
attacked the foliage but also the flower stems. By the end of the season, the
plants were large with many leaves, which made thorough spraying difficult and
the disease problem worse. Experiment with trying to rejuvenate plants near the
end of the season by removing some of the older foliage to increase air
circulation and allow more light to penetrate to the crown. We also had
problems with thrips, whiteflies and Botrytis.


Linaria Lace and poppy Temptress cut stems were subjected to
a variety of tests to determine ethylene sensitivity, optimum cold storage
duration, pretreatments and pulses, vase solutions and substrates, and
commercial preservatives. After treatment, stems were placed at 68° F under
330-500 foot-candles for 12 hours per day to simulate a retail or consumer

Two points are critical in the marketing of a cut flower:
When it is no longer marketable and when the consumer would typically dispose
of the flower. Flowers were monitored daily to determine the end of retail vase
life, which was designated as the first day a change was noticed in the flower
or inflorescence that would typically prevent the flower from being sold by a
wholesaler or retailer. The consumer vase life was designated as the day a
typical consumer would have disposed of the stem. For poppies, the end of a
retail vase life was noted when flowers no longer had a cup shape, and the end
of consumer vase life occurred when a petal abscissed or became crinkled,
discolored or the stem collapsed. For linaria, the end of retail vase life
occurred when immature florets opened pale or when more than 50 percent of the
spike was open, and the end of consumer vase life occurred when the stem
collapsed or more than 75 percent of florets were discolored or shriveled.

Linaria. Lace Violet
is an excellent filler flower with a consumer vase life of 5-7 days that could
be increased to 10-19 days with various treatments, including commercial
holding solutions such as Floralife Professional and Chrysal Professional 2
Processing Solution, 2 or 4 percent sucrose in the vase solution, and citric
acid plus 8-HQS. Stems were harvested when five florets were open. Treating
linaria with either 0.1 or 1.0 ppm ethylene, 1-MCP (Ethylbloc) or STS (AVB) had
no effect on retail or consumer vase life, indicating that poppies are not
ethylene-sensitive flowers. Stems should not be cold-stored for very long but
can be used in floral foam with only a Á slight decrease in vase life.
With proper handling, linaria is suitable for both retail and wholesale

Lupine. While we did
not conduct postharvest evaluations on lupine Sunrise, the cut stems lasted 6-8
days. Growers recommend using a floral holding solution with Sunrise. Other
lupines are sensitive to ethylene, indicating that they should be treated with
an anti-ethylene agent such as STS or 1-MCP to delay petal drop. Stems were
harvested when 4-5 of the lower florets were open.

Poppy. Temptress is
a spectacular flower with a relatively short vase life of six days when
harvested fully open, which could be increased to 7.6-7.9 days by using
commercial holding solutions such as Floralife Professional and Chrysal
Professional 2 Processing Solution. Interestingly, the 10 percent sucrose
pulse, commercial hydration solutions, and 2 or 4 percent sucrose vase
solutions increased retail vase life but had no effect on consumer vase life.
Treating poppy with either 0.1 or 1.0 ppm ethylene, 1-MCP or STS had no effect
on retail or consumer vase life, indicating that poppies are not ethylene
sensitive flowers. Stems can be readily stored for one week at 36° F. In
contrast to many cut flowers, poppies can be used in floral foam with no
negative effects. Without proper treatment, poppy is best suited to retail
sales; however, because flowers tolerate cold storage very well, poppies are
suitable for wholesale marketing with proper handling. Poppies can be harvested
in the cracked bud stage for easy shipping. Be sure to look for petal color.
However, a percentage of the buds, approximately 10 percent, will never fully
open. For bucket sales, harvest fully open; vase life will still be six days.

Linaria and lupine may be new to most of your customers,
which will necessitate some education. Poppies always attract attention, but
many buyers are concerned they won't last long. Be sure to tell them that they
have a six-day vase life that goes up to over seven days when place in floral
preservative and that the flowers can be used in floral foam.

This research was supported by the American Floral Endowment
and by Hill Foundation of the International Cut Flower Growers Association.
Linaria seed was provided by American Takii and poppy plugs by Peregrine Farm.
Appreciation is expressed to Ingram McCall and Diane Mays for data collection
and to Judith Thomas and the North Carolina State University Phytotron staff
for technical support. Thanks also to Sarah Levitt and Michael Turner for providing
marketing and pricing information.

About The Author

John Dole, Sylvia Blankenship and Bill Fonteno are professors; Frankie Fanelli and Lane Greer are graduate research assistants and Beth Harden is a research technician at North Carolina State University's Department of Horticultural Science. They can be reached by phone at (919) 515-3537 or E-mail at

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