 ‘Vivas Salmon Pink,’ ‘Katz Cherry Blossom’ and ‘Cheerful Yellow’ |
Stock (Matthiola incana) is a little appreciated workhorse of the cut flower industry. It offers wonderful fragrance and a broad range of colors.
Production, shipping limitations
Stock production in the United States is done primarily outdoors and is limited to areas with temperatures low enough to provide flower initiation and high-quality stems. These are areas where the temperatures are not so low as to damage plants, which usually means only light to moderate freezes.
Most commercial production has been in coastal California with flowers shipped nationwide. However, growers in parts of the Southeast can also produce high-quality stock during winter, and growers in the North can do the same in spring and early summer. Smaller amounts of stock are grown in spring across the United States and Canada.
The increased use of greenhouses and hoop houses for season extension of cut flower production presents another opportunity to grow stock for local markets.
While stock can handle cold storage well, its leaves are somewhat brittle and tend to crack when packed and shipped in boxes. The foliage also tends to yellow fairly quickly, especially when stored and shipped.
Production options
For many years, growers had two options regarding stock cultivars: traditional types and minimal-cold-requirement types.
Traditional types are tall, up to 3 feet, but require a cold treatment of 50°F-55°F for at least 10 days for early-flowering cultivars and three weeks for late-flowering cultivars. Many colors are available.
The cultivars in the traditional group can be divided into selectable and non-selectable plants. While double-flowered stock are more valuable commercially, no series available produces 100 percent double flowers. Most stock cultivars produce 50-60 percent doubles and 40-50 percent singles.
Seedlings of selectable types can be sorted into doubles and singles with some practice and the right environmental conditions. Selectable series include Glory and Goldcut. Non-selectable cultivars are a mixture of singles and doubles and include 'American Beauty,' 'Lilac Lavender,' 'Miracle Rose Pink' and 'Pacific Blue.'
Minimal-cold-requirement types are white or cream-colored cultivars that flower with little or no cold treatment and a short crop time, 10-14 weeks from sowing to flower. These cultivars are almost all doubles (about 90 percent) and better adapted to greenhouse or hoop house production. Cultivars include 'Cheerful White,' 'Cheerful Yellow' and 'Regal White.'
Minimal cold requirements
Both Sakata Ornamentals' Vivas series and PanAmerican Seed's Katz series require little or no cold treatment. These series can initiate flowers at relatively mild temperatures (55°F-60°F), eliminating the cold treatments necessary for most cultivars. This feature makes them suitable for greenhouse and season-extending hoop house production. Hoop houses can be used to protect plants from the worst cold weather that can cause damage.
Plant quality is best at low production temperatures (50°F-55°F), but plants can grow well under higher temperatures (up to the low 80s during the day). They are available in more colors, including various shades of rose, pink and purple. Unfortunately, they only produce 60 percent doubles. Plants are not as tall (about 2½ feet) as traditional column types and as with all stock cultivars, they don't like high temperatures (above 62°F at night or above 85°F during the day) during production.
The Katz series was initially sold as Mambo, but was changed to honor deceased PanAmerican Seed breeder and cut flower specialist Philip Katz.
Stock production
'Vivas Blue' plants were grown from 392 plugs in a greenhouse at North Carolina State University. Large plastic flats (20¾ by 15 inches, 4½ inches deep) were filled with a commercial peat-based medium. Plugs were planted in a 4-by-6 pattern, 3 inches-by-3 inches apart, resulting in 24 plants per tray. Bulb crates would work equally well. For part of the crop, standard shallow bedding plant flats (10½ by 21 inches, 2½ inches deep) were used. They worked well, but the growing medium dried out faster due to having less volume in the flat.
Plants were grown at minimum temperatures of 55°F night and 65°F day, although many nights and days were warmer. Plants were irrigated with 150 parts per million nitrogen from either a 20-10-20 or 13-2-13 fertilizer, as needed. While the stems are quite stocky (no pun intended), one or two layers of support netting should be used in the greenhouse to hold up the heavy inflorescences.
Timing of the crop varied with the planting date. Plugs were planted on three dates: Jan. 13, Jan. 20 and Feb. 10. The finished crops started flowering March 14, March 22 and April 3, respectively. The crop schedule was 7½ to nine weeks from plugs.
Postharvest handling
Stems were harvested into water in the greenhouse when at least one floret per stem was open. The stems were sorted according to number of open flowers and stem caliper, recut to 18 inches, and placed in the appropriate treatments. Unless otherwise indicated, the floral solution used in all experiments was 72°F deionized water (similar to distilled water). After treatment, stems were placed (one per vase) at 72°F under approximately 100 footcandles for 12 hours per day at 40-60 percent relative humidity.
Vase life was considered finished when open flowers were more than one-third dead or two-thirds wilted. There were usually a significant number of wilted flowers along with the minimum one-third dead flowers.
Postharvest results
Vase life of 'Vivas Blue' stems averaged 11-12 days without any treatments, and the cultivars had rather simple needs in terms of postharvest. Floral holding and hydrating solutions and sugar pulses had little effect. Interestingly, while stock is often thought to be sensitive to ethylene, exogenous ethylene had no effect and neither did either of the anti-ethylene agents, STS and 1-MCP.
'Vivas Blue' not only tolerated cold storage well, but storing stems dry at 36°F for one or two weeks actually increased vase life by one to three days. This trend showed up in two experiments and is quite surprising, considering how poorly most cut flower species handle storage.
Another interesting finding was the effect of floral foam on cut stock stems. Many cut flower species are negatively affected by floral foam, which is why we include it in routine testing procedures.
Vase life of 'Vivas Blue' was increased by up to several days when floral foam was used. One reason could be that the foam reduced the pH of the vase solution. Another reason could be that the foam increased the soluble salt content of the water. However, in another trial comparing deionized and tap water, which had a higher soluble salt content, no differences occurred.
Using either 2 or 4 percent sucrose in the vase water caused the flowers to turn much darker purple. The longest vase life occurred when we used 2 percent sucrose with floral foam. No commercial floral preservatives were trialed with foam, but they are likely to have a similar effect.
Erin Regan is a former graduate research assistant and John Dole is a professor, North Carolina State University, Department of Horticultural Science, (919) 515-3537; john_dole@ncsu.edu.
The authors thank Ingram McCall, Diane Mays, Emma Locke, Erin Possiel and Eric Olson for assisting in the production and harvest, and Roland Leatherwood for assisting in ethylene studies. We are very much appreciative of American Floral Endowment for funding the work and Sakata Seed America for providing the stock plugs.
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