Hot New Cuts for a Cool Greenhouse By John M. Dole, Frankie Fanelli, Beth Harden, Sylvia Blankenship, Bill Fonteno and Lane Greer

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 workingwith three species that have great potential for cool temperature greenhouses.Linaria Lace produces tall open spikes of small rose, violet, white or yellowsnapdragon-like flowers. Lupine ‘Sunrise’ has spikes of mildly fragrant, blueflowers 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-offcolors including white, orange, yellow, salmon, rose and pink. Compared withMeadow Pastels, Temptress has longer, thicker stems, longer postharvest lifeand slightly stronger colors. However, Meadow Pastels is generally much easierto germinate and has a higher germination percentage than Temptress. Somegrowers have had few problems germinating Temptress while many others have hadlittle success. In fact, germination problems led us to use Meadow Pastels forthe production studies instead of Temptress.

Our goal for the production experiments was to developeconomical production protocols, examining production temperature, transplantage and supplemental lighting of the plugs. The postharvest work determinedethylene sensitivity, optimum cold storage duration, pretreatments and pulses,vase solutions and substrates, and commercial preservatives for linaria andpoppy.


Linaria ‘Lace Violet’, lupine Sunrise and poppy MeadowPastels seeds were directly sown into 105 plug flats using a peat-basedcommercial media and germinated at 60° F. One half of the plants receivedambient light plus eight-hours of HID supplemental lighting, and the other halfof the plants were placed under ambient light. Average light levels were 2,145foot-candles for ambient light and 2,700 foot-candles for HID supplementallighting, measured daily at noon. Seedlings were transplanted at the appearanceof 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 UniversityPhytotron, and lupine seedlings were placed at 59, 64 or 69° F nighttemperatures in a polyethylene covered-greenhouse. Day temperatures were10-17° F higher than night temperatures. Linaria seedlings weretransplanted into 4-inch pots spaced pot to pot, and lupine and poppy seedlingswere transplanted into 6-inch pots spaced pot to pot initially. The poppieswere later spaced to 9-inch centers. We used pots for the experiments becausewe had to move the plants. However, all three species can be easily grown inbeds. Plants were irrigated with 150 ppm nitrogen from a premixed commercial20-10-20 fertilizer during the week and with clear water on the weekends.

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

Linaria. Linariaproved to be an excellent flower producer, with each plant producing from4.2-10.0 cut stems. Optimum production temperature was 50° F. Flowersproduced in 59° F were unmarketable, while 41° F productiontemperatures produced longer and thicker stems, though production time wasgreatly increased. Do not grow this plant warm or the stems will be thin, shortand completely unusable. In our work, the first plants to flower were growingat 59° F, and we thought we had a dud on our hands. However, we completelychanged 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 2-3leaf stage to maximize stem number, length and profitability, which wasestimated at $4.74 per plant. The close spacing allows for many harvestablestems to be produced in a small area. Problems included thrips and root rot ona few plants. Note that when transplanting, the seedlings form branches verylow on the plant, which can appear to be separate seedlings.

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

Poppy. Poppy wasalso an excellent flower producer, with each plant producing from 3.1-6.6 cutstems in the experiment and up to 12 stems per plant in later work. The59º F temperature was optimal, as it produced the longest stems in theshortest time. At that temperature, plants should be transplanted at the 2-3leaf stage. Supplemental HID lighting had a negligible effect and did notinfluence profitability, which averaged $0.99 per plant.

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


Linaria Lace and poppy Temptress cut stems were subjected toa variety of tests to determine ethylene sensitivity, optimum cold storageduration, pretreatments and pulses, vase solutions and substrates, andcommercial preservatives. After treatment, stems were placed at 68° F under330-500 foot-candles for 12 hours per day to simulate a retail or consumerenvironment.

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

Linaria. Lace Violetis an excellent filler flower with a consumer vase life of 5-7 days that couldbe increased to 10-19 days with various treatments, including commercialholding solutions such as Floralife Professional and Chrysal Professional 2Processing Solution, 2 or 4 percent sucrose in the vase solution, and citricacid plus 8-HQS. Stems were harvested when five florets were open. Treatinglinaria with either 0.1 or 1.0 ppm ethylene, 1-MCP (Ethylbloc) or STS (AVB) hadno effect on retail or consumer vase life, indicating that poppies are notethylene-sensitive flowers. Stems should not be cold-stored for very long butcan be used in floral foam with only a Á slight decrease in vase life.With proper handling, linaria is suitable for both retail and wholesalemarketing.

Lupine. While we didnot conduct postharvest evaluations on lupine Sunrise, the cut stems lasted 6-8days. Growers recommend using a floral holding solution with Sunrise. Otherlupines are sensitive to ethylene, indicating that they should be treated withan anti-ethylene agent such as STS or 1-MCP to delay petal drop. Stems wereharvested when 4-5 of the lower florets were open.

Poppy. Temptress isa spectacular flower with a relatively short vase life of six days whenharvested fully open, which could be increased to 7.6-7.9 days by usingcommercial holding solutions such as Floralife Professional and ChrysalProfessional 2 Processing Solution. Interestingly, the 10 percent sucrosepulse, commercial hydration solutions, and 2 or 4 percent sucrose vasesolutions 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 effecton retail or consumer vase life, indicating that poppies are not ethylenesensitive flowers. Stems can be readily stored for one week at 36° F. Incontrast to many cut flowers, poppies can be used in floral foam with nonegative effects. Without proper treatment, poppy is best suited to retailsales; however, because flowers tolerate cold storage very well, poppies aresuitable for wholesale marketing with proper handling. Poppies can be harvestedin 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 fullyopen. 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, butmany buyers are concerned they won’t last long. Be sure to tell them that theyhave a six-day vase life that goes up to over seven days when place in floralpreservative and that the flowers can be used in floral foam.

This research was supported by the American Floral Endowmentand 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 collectionand to Judith Thomas and the North Carolina State University Phytotron stafffor technical support. Thanks also to Sarah Levitt and Michael Turner for providingmarketing and pricing information.

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John M. Dole, Frankie Fanelli, Beth Harden, Sylvia Blankenship, Bill Fonteno and Lane Greer

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 [email protected]

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