Postharvest of Specialty Cut Flowers – North Carolina State Report
Second part of article originally published in Volume 17, Number 1, January 2005
This project was supported by the American Floral Endowment, the Association of Specialty Cut Flower Growers, and numerous suppliers. The authors would like to thank Ingram McCall, Diane Mays, Aliya Donnell, and Leslie Tichner for growing the cut flowers and for assisting with the postharvest studies.
Working with new cut flowers is fun. We get to see and enjoy the latest species available. During the summer our coolers are filled with an ever-changing display of colors and species. It is a great business to be in. This year was no different as we had many new cultivars to work with and a number of them had long postharvest lives. The NSCU postharvest research process consists of two stages. Stage I. Each year an initial postharvest screening is conducted on the most promising species/cultivars from the seed, perennial, and woody trials. This year we screened 21 new cut flower species/cultivars. Those with the longest vase life included Adenophora ‘Amethyst’, Ammi ‘Casablanca’, Campanula ‘Heavenly Blue’, Dianthus ‘Sweet Coral’ and ‘Sweet Red’, Eustoma ‘Twinkle Blue Blush’ and ‘Twinkle Pink’, Matricaria ‘Magic Lime Green’, Helleborus hybrids, Persicaria ‘Silver Dragon’ and Zinnia ‘Oklahoma Carmine’ and ‘Yellow’. Stage II. In this stage four cultivars were produced in large quantities and subjected to extensive postharvest testing exam-ining ethylene sensitivity, anti-ethylene agents, op-timum cold storage duration, pretreatments and pulses, vase solutions and substrates, and commercial preservatives. This year we studied Lupinus ‘Sunrise’, Trachelium ‘Jemmy Royal Purple’, Zinnia ‘Benary’s Scarlet Giant’, and Zinnia ‘Sungold’. Photos are on page 33.
Lupine ‘Sunrise’ – Stage 2
One new cut flower, Lupinus hartwegii ssp. cruikshankii ‘Sunrise’ (Photo 1), produces tall, mildly fragrant spikes with pea-shaped florets that are blue with a touch of white and yellow. The deep green foliage, typical of lupines, and the long, strong stems add substance to this cut flower. The optimum growing temperature for this cool-season plant is 59oF.
Greenhouse-grown lupine ‘Sunrise’ cut stems were harvested when 1 to 4 florets were fully opened. After treatment, stems were placed at 68+4oF under approximately 200 ftc light for 12 hrs/day. Flowers were monitored daily to determine the end of the consumer vase life which occurred when a stem collapsed or more than 50% of florets were discolored, shriveled or dropped.
Commercial pretreatments and 24 hr 10 or 20% sucrose pulse had no effect. Vase life of the control treatment averaged 9 days.
Cold storage at 34oF for up to two weeks in a high quality water resulted in a 9 day vase life. As with many spike-type flowers, the stems curved after being removed from storage (Photo 2).
The lupine stems were ethylene sensitive. When exposed to either 0.1 or 1.0 ppm ethylene, the florets and buds abscised and buds failed to open. The stems pretreated with STS had a vase life of 10 days at the 0.1 ethylene concentration and a 6.3 day vase life at the 1.0 concentration (Graph 1).
Graph 1. Effect of exogenous ethylene (0 or 1.0 ppm) and anti-ethylene agents on lupine ‘Sunrise’.
The use of commercial holding solutions (Chrysal Professional 2 Processing Solution and Floralife Professional) either increased vase life an average of 2 days or did not have an effect (Graph 2). The use of floral foam had no effect on vase life.
Graph 2. Effect of Chrysal Professional 2 Processing Solution (CP2), Floralife Professional (FLP), or water on lupine ‘Sunrise’.
Lupine ‘Sunrise’ is a good cut flower with a consumer vase life of 9 to 11 days. ‘Sunrise’ has a high degree of commercial potential due to its spike inflorescence, long strong stem, and unusual foliage. The mild, pleasant fragrance along with the unique tri-color florets makes this cut flower highly useful for bouquets or single species bunches. The stems also add dimension to arrangements with no detrimental effects when used with floral foam. This lupine is suitable for local and wholesale marketing.
The optimum handling procedures for cut lupine ‘Sunrise’ are to:
1. pretreat with STS or 1-MCP,
2. place in commercial holding solutions,
3. cold store at 34 oF for two weeks or less.
Trachelium – Stage 2
One cut flower new for the United States, trachelium (Photo 3), produces tall slender stems topped by masses of tiny star-shaped florets that form a flattened head ranging from 3 to 6 inches in diameter. The purple, rose or white flowers fill out bouquets or arrangements, blending softly with about any color.
Greenhouse-grown trachelium ‘Jemmy Royal Purple’ stems were harvested when 25% of the florets in a head were open. After treatment, stems were placed at 68+4oF under approximately 200 ftc light for 12 hrs/day. Flowers were monitored daily to determine the end of wholesale/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. This occurred when the florets were no longer uniform in appearance. The consumer vase life was designated as the day a typical consumer would have disposed of the stem. This occurred when the undersides of the florets turned brown or when the florets closed and/or did not continue to open.
Pulsing with 10% or 20% sucrose reduced the vase life.
Trachelium were sensitive to ethylene. At 0.1 or 1.0 ppm the florets either closed entirely or did not continue to open (Photo 4). The application of 1-MCP or STS prevented the open florets from closing and encouraged opening of some new florets.
Pretreatments/Simulated Shipping and Storage
Stems were pretreated with STS, 1-MCP, or water and stored at 41oF for four days dry or wet in holding preservative or high quality water. Stems tolerated 4 days of storage well regardless of pretreatment resulting in a vase life of 9 to 13 days. However, fewer of the florets opened on the stems that were stored than on unstored stems. A subsequent test was conducted with stems harvested when 75% of the florets were open and stored at 34oF, 41oF or 68oF for three days in water. The wholesale/retail vase life for the stems stored at 34oF and 41oF was 4 days and the consumer vase life was 9 days. Those stored at 68oF had a 2 and 6 day wholesale/retail and consumer vase life, respectively.
In a longer term storage study, the 14 day consumer vase life of unstored flowers was reduced to 9 days and 5-7 days after 1 and 2 weeks, respectively, at 34 oF (Graph 3).
Graph 3. Effect of wet or dry cold storage on vase life of trachelium ‘Jemmy Royal Purple’.
Stems held in 2 or 4% sucrose had a longer wholesale/retail and consumer vase life compared with water only (Graph 4). The use of floral foam was not detrimental when used with sucrose solutions. However, floral foam without sucrose reduced the consumer vase life.
Graph 4. Effect of floral foam and sucrose in the vase solution on trachelium ‘Jemmy Royal Purple’.
The use of commercial holding solutions produced varied results based on the product. The stems held in Chrysal Professional 2 Processing Solution had a wholesale/retail vase life of 10 days and a consumer vase life of 18 days compared with 9 days wholesale/retail vase life and 15 days consumer vase life for the controls in water. The stems held in Floralife Professional had a wholesale/retail vase life of 8 days and a consumer vase life of 11 days. Combining the commercial hydrators with holding solutions produced a wholesale/retail vase life of 8 to 9 days and a consumer vase life of 11 days for both products.
Trachelium ‘Jemmy Royal Purple’ is a showy filler flower with a consumer vase life averaging 15 days that can be increased to 18 days with 2% sucrose in the vase solution. Stems may be included in floral foam arrangements for a consumer vase life of 10 days that can increased to 21 days with a 2% sucrose holding solution. When cold storing, the stems should be cut at the desired stage of openness as the florets do not open well after storage. However, consumer vase life was unaffected by cold storage. Trachelium is sensitive to ethylene and anti-ethylene agents should be used. With proper handling trachelium is suitable for both local and wholesale marketing.
The optimum handling procedures for cut trachelium ‘Jemmy Royal Purple’ are to:
1. cut into clean high quality water,
2. place in 2% sucrose solution, especially if using
3. cold store at 34 oF for one week or less.
Zinnias – Stage 2
Zinnias continue to be popular with cut flower buyers and breeders alike. Two cultivars, ‘Benary’s Giant Scarlet’ (Photo 5) and ‘Sun Gold’ (Photo 6) were tested to determine the optimum handling procedures to extend postharvest life. Prior testing has shown that zinnia cultivars may respond differently to postharvest techniques than many other cut flowers.
Zinnia ‘Benary’s Giant Scarlet’ and ‘Sun Gold’ cut stems were harvested when two to several rows of petals were expanded. After treatment, stems were placed at 68+4oF under approximately 200 ftc light for 12 hrs/day. Flowers were monitored daily to determine the end of consumer vase life which was designated as the day a typical consumer would have disposed of the stem. This occurred when the petals curled and began to turn brown at the tips or when the stem collapsed.
Stems could not be cold stored for one week at 34oF. Both cultivars wilted and exhibited cold damage regardless of being stored dry or wet. Cold storing ‘Sun Gold’ flowers resulted in flower petal browning and stem collapse, while ‘Benary’s Giant Scarlet’ showed yellow patches on the red petals (Photo 7) and stem collapse. The yellow patches on the petals of ‘Benary’s Giant Scarlet’ were observed a day or two after cold storage. Treating the stems with either 0.1 or 1.0 ppm ethylene, 1-MCP, or STS had no effect on consumer vase life, indicating that zinnias are not ethylene sensitive flowers.
Pretreatments/Simulated Shipping and Storage
Stems were pretreated with STS or 1-MCP and stored at 41oF for four days dry or wet in holding preservative and a high quality water. The stems with no pretreatment but stored in a holding preservative had a consumer vase life of 14 to 16 days, an increase of 2 to 4 days compared with no preservative. The stems stored dry (Photo 8) regained turgidity and averaged a vase life of 14 days; however, the petals remained slightly twisted and curled after being in the vase for several days.
Both zinnia cultivars had a 19 to 20 day vase life in clean, high quality water. The use of hydration or holding solutions resulted in a similar vase life of 19 to 20 days or decreased vase life slightly to 16 to 17 days.
Sucrose and Floral Foam
A 24-hr 10 or 20 % sucrose pulse decreased the vase life of both cultivars. The 10% sucrose pulse decreased the consumer vase life of ‘Benary’s Giant Scarlet’ to 14 days and ‘Sun Gold’ to 11 days. The 20% pulse decreased the vase life of both cultivars to 10 days. Stems held in floral foam had a vase life of 9 -10 days compared to 12-15 days in water only (Graph 5). Adding 2% sucrose to the vase when using foam increased the vase life of ‘Benary’s Giant Scarlet’ by 2 to 3 days, while it had no effect on ‘Sun Gold’.
Graph 5. Effect of floral foam on vase life of zinnia ‘Benary’s Giant Scarlet’ and ‘Sun Gold’.
Zinnia ‘Benary’s Giant Scarlet’ had a large red flower while ‘Sun Gold’ was a brilliant yellow gold with a slightly smaller flower (Photos 5 and 6). Both cultivars had a long vase life of 19 to 20 days when held in water only with no commercial hydration or holding preservative. Both cultivars exhibited cold storage damage at 34oF; however, 41oF storage worked well. Stems stored at 41oF with commercial holding preservative resulted in a vase life of 14 to 16 days. Both zinnia cultivars are suitable for the local or regional retail market.
The optimum handling procedures for cut zinnias are to:
1.cut into clean high quality water,
2. store in a holding preservative or 2% sucrose solution, especially if using floral foam,
3.cold store at a minimum of 41 oF for four days or less.