John B. Young and Jeff S. Kuehny

Specialty cut flowers, or nontraditional cut flowers, have become increasingly important in agriculture. Typically, specialty cut flower growers are owners of small acreages that have the basic equipment for producing a horticultural crop. These growers enter the market on a small scale, usually selling their cut flowers at a farmers market, to an independent grocer or directly to a wholesale or retail florist. Maintaining a diverse product mix and a quality cut flower is vital to the growth of the specialty cut flower industry.

Growing specialty cut flowers is also dependent on a combination of climatic factors that affect flower quality and yield. The U.S. Gulf Coast has a mild winter climate that provides an earlier growing season than other parts of the country and a hot humid summer climate. The effect of climate can have both a positive and negative impact on production. To study how these factors affect production in Louisiana, four species of cut flowers were selected – gladiolus, celosia, sunflower and zinnia.

These species were planted to determine the number of days from planting to bud and the number of days from bud to harvest for four scheduled plantings of each species. The objective of this research was to determine pro-duction times so that a production schedule can be set for continuous production of product for the market. All crops were grown in an open field at Burden Center in Baton Rouge.

Plants were grown on 285-foot rows, 4 feet wide by 12 inches high in an Olivier silt loam soil. Soil tests were taken, and the pH was adjusted using limestone. Granular 13-13-13 fertilizer was incorporated, and further fertiliza-tion was applied through drip irrigation using a 20-10-20 liquid fertilizer. Solar radiation, air and soil temperatures were recorded over the growing period.

The average number of days to emergence (2001 and 2002) for gladio-lus was 28 days for the earlier plantings (plantings 1 and 2 in February and March) and 15 days for the later plant-ings (plantings 3 and 4 in March and April). Therefore, the number of days to emergence was significantly affected by planting date by approximately two weeks.

The average number of days from emergence to bud was 57 days for the earlier plantings, and 53 days for the later plantings. The average number of days from bud to harvest was 7 days for the earlier plantings and 9 days for the later the plantings. The time from emer-gence to bud and bud to flower was not affected by planting date.

The days to emergence is the most significant factor affecting the number of days from planting to harvest. This did not affect days from planting to harvest in 2002, as days from emergence to bud increased by planting date. This increase could not be attributed to dif-ferences in air or soil temperature, or solar radiation. Table 1 indicates the average number of days for each stage of development, the average number of days from planting to harvest and the average stem length over the 2001 and 2002 growing season.

These results suggest that later planting dates may result in fewer days to harvest because of fewer days to emergence. The average days from emergence to bud, however, may negate this effect where the average days from plant to harvest may be similar.

Celosia is classified as a quanti-tative short day plant, which means it must have short days to flower. How-ever, the number of days to harvest was slightly greater under short daylengths and cool temperatures. The average number of days (2001 and 2002) to bloom for the earlier plantings in March and April was 43 days; for the later plantings in April, May and June, it was 39 days. The number of days from bloom to harvest for the earlier plantings was 35 days, and for the later planting date, it took 27 days. See Table 2.

Scheduling celosia at two-week intervals beginning in early March, then at three-week intervals for plantings beginning in May should provide a consistent supply, although stem length may be shorter for later plantings.

Sunflower

The number of days from planting to bud is the most signif-icant developmental stage when scheduling sunflower because it takes the longest. It took an average of 39 days to bud for both years for the earlier plantings in March and April (1 and 2) as well as for the later plant-ings in April, May and June (3 and 4). The number of days from bud to harvest took an average of 17 days for the earlier plantings and 21 days for the later planting dates. Sunflower was harvest-ed an average of 57 days after planting from March to July, but was delayed by an average of 26 days for the third planting in 2001.

Although the number of days to bud can vary over time, it is recommended that sunflower be scheduled at two-week intervals throughout the growing season for optimal production. See Table 3.

Zinnia

The average number of days from planting to bud over both years for earlier plantings in March and April (1 and 2) was 34 days, while the later plantings in April, May and June (3 and 4) took an average of 35 days. The average number of days from bud to harvest was 17 days for the earlier plantings, but for the later plantings, it was 13 days.

Since zinnia is a fast-growing plant that may produce numerous stems over several months, it can be scheduled at three-week intervals to provide high yields throughout the growing season.

Postharvest of Sunflower

It is a common belief that pollen-less varieties of sunflower have a greater postharvest life than pollen-producing cultivars. This may be due to pollen-less cultivars generally producing little or no pollen allowing for no pollenization and therefore more energy to prolong vase life. Postharvest longevity studies were conducted under simulated interior conditions at 75 degrees F and florescent light levels at 60 footcandles to deter-mine differences in longevity of pollen-less (PL) and pollen-producing (PP) varieties. Although some pollen-less varieties, Full Sun and Sunbright, demonstrated greater longevity than pollen-producing cultivars, Valentine (PP) had greater longevity than Claret (PL) and Joker (PL).

Guidelines for Growers

These results provide guidelines for the spring growing season along the Gulf Coast. These guidelines can be used to assist growers in planning market dates through crop scheduling. Climatic changes caused by fluctuations in temperatures, rainfall and solar radia-tion, however, may affect stages of development and thus total days to harvest.

Acknowledgments

The Ione Burden Memorial Assistantship in Horticulture, Scotts Company, The Fred C. Gloeckner Company, Pan American Seed and Patricia C. Branch, research associate in horticulture, for her assistance on this project.

John B. Young, former Graduate Student, and Jeff S. Kuehny, Associate Professor, department of Horticulture, LSU AgCenter, Baton Rouge La.

(This article was published in the spring 2005 issue of Louisiana Agriculture.)