UF/IFAS - Vegetarian Newsletter

Consumers continue to be fascinated with new types of fresh produce, and with this fascination edible flowers are making inroads into all kinds of recipes. I recently did web search and came up with over 300,000 sites having to do with them! Sites like http://starchefs.com/ and http://whatscookingamerica.net describe culinary uses and tips for literally dozens of flowers from allium to yucca, while the Cornell Book of Fresh Herbs and Edible Flowers serves as an excellent desktop reference. The creative uses for flowers are truly amazing, ranging from raw garnishes, to stuffed and baked dishes, to infusion in sauces or seasoned oils, to infusion with sugar solutions for desserts (Figure 1). They not only make dishes more attractive, but can also be selected for their unique flavors.

As with all fresh produce, food safety is important, and edible flowers are no exception. First of all, know that all flowers are not edible, so check to be sure on this point. Secondly, knowledge of the production history is important to avoid purchasing flowers that have been treated with pesticides not labeled for fresh produce. This includes flowers grown as ornamentals rather than as edibles. Only registered pesticides should be used when growing edible flowers and re-entry times and preharvest intervals should be strictly followed.

As demand for edible flowers increases, commercial shippers need handling and shipping information for these delicate products. Very little postharvest information has been published for edible flowers. Recommendations were developed for four common edible flowers (Table 1).

Table 1. Recommended storage temperatures and expected storage life of selected edible flowers. (from Kelley et al., 2002)
Flower Species	Storage Temperature	Expected Storage Life
Pansy (V. x wittrockiana L)	-2.5 to 2.5 °C (27 to 36 ^oF) >2.5	14 days 7 days
Nasturtium (Tropaeolum majus L)
Viola (Viola tricolor L)
Scarlet runner bean blossoms (Phaseolus coccineus L)	0 to 10 °C	7 days

Yellow summer squash flowers. For many years, numerous specialty vegetables have been grown and evaluated under protected culture by the University of Florida/IFAS at two locations in north Florida, the North Florida Research & Education Center-Suwannee Valley in Live Oak and the Horticulture Research Unit (HRU) in northwest Gainesville. Research at the HRU facility was discontinued last fall and moved to new facilities at the Plant Science Research & Education Unit in Citra, where Dr. Dan Cantliffe and his team continue their studies on several crops, including melons, squashes, color pepper, Beit Alpha cucumber and strawberry. Competition from imported, greenhouse-grown vegetables may encourage expansion of specialty vegetables grown under protected culture in Florida (Cantliffe and Vansickle, 2001).

Yellow summer squash, in particular, produces large male and female blossoms up to 7.5 cm (3 inches). The flowers open in early morning and remain open only for that day, making them highly perishable. Male squash blossoms are borne on long stems, whereas female flowers consist of a short stem, the growing fruit and the bloom. An abscission zone forms at the base of the blossom, allowing the baby squash to be detached for sale as a separate product (Figure 2). There is potential to increase production of squash flowers in Florida, where each flower may fetch as much as $1.00.

In 2003, we obtained yellow summer squash blossoms (‘Dixie’) from the trials at the HRU and conducted experiments designed to determine basic postharvest information that would be useful to commercial shippers. These results were reported at the 2004 International Symposium on Protected Culture in a Mild-Winter Climate held in March in Orlando (Villalta et al, 2004).

Male and female flowers (closed at harvest) were clipped and placed into hinged, 2-liter polystyrene (clamshell) containers, three blossoms per container. The immature fruits were detached from the flowers since our previous tests showed that the flowers stored longer with the fruits removed. The containers were immediately transported to the Postharvest Horticulture Laboratory at the Horticultural Sciences Department in Gainesville. Female blossoms weighed 8 to 10 g, while diameter (at widest girth) was 17 to 25 mm (3/4 to 1 inch) and length ranged from 55 to 60 mm (2 to 2.5 inches). Male and female blossoms were stored in the same container at 2.5 or 5.0 °C (36 or 41 ^oF, respectively). Flowers were considered unmarketable when they showed petal necrosis, water-soaking, mycelial growth or wilting.

The blossoms remained marketable for 7 days at both temperatures; water loss was 2.0 to 2.5% and appearance was good (Figure 3). However, after 14 days of storage they were unmarketable due to desiccation, development of decay, petal necrosis and collapsed tissue.


Figure 3. Appearance remained good for male blossoms (left) and female blossoms with fruits detached prior to storage (right) after 7 days at 2.5 ^oC and 5 ^oC (not shown). (Photo courtesy: Alfredo Villalta)

In a separate test, the respiration rate was determined on female squash blossoms (‘Dixie’) stored at 5 and 10 °C (41 and 50 °F, respectively). The respiration rate of blossoms stored at 5 °C remained constant and extremely high during storage, averaging 76 mg-kg^-1-hr^-1. Blossoms stored at 10 °C produced almost twice the CO₂ (195 mg-kg^-1-hr^-1) as those stored at the lower temperature after 1 day. During the first 4 days of storage, the respiration rate of the blossoms at 10 °C decreased by about one third and then remained constant for 2 more days. However, blossoms stored at 10 °C were unmarketable after only 2 days. In contrast, summer squash fruit is reported to respire at moderate rates, about 30 mg-kg^-1-hr^-1 at 5 ^oC and about 65 mg-kg^-1-hr^-1 at 10 ^oC (McCollum, 2004).

Recommendations. Summer squash fruit harvested at normal size is chilling sensitive and will develop chilling injury within several days of storage at 5 to 10 ^oC. Squash blossoms in these tests, however, were more resistant and were successfully stored for 7 days at 2.5 ^oC. Rigid, vented containers, such as clamshells, are recommended for these delicate flowers during handling and shipping because they:

Further tests will be conducted to evaluate other methods to further extend the postharvest quality of squash blossoms.

Cantliffe, D.J. and J.J. Vansickle. 2001. Competitiveness of the Spanish and Dutch greenhouse industries with the Florida fresh vegetable industry. Proc. Fla. State Hort. Soc. 114: 283-287.

Kelley, M.K., Cameron, C.A., Biernbaum, A.J., and Poff, L. 2003. Effects of Storage Temperature on the Quality of Edible Flowers. Postharvest Biol. and Technol. 27:341-344.

Lauderdale, Cyndi. 1999. Edible Flowers. Department of Horticultural Science, College of Agriculture & Life Sciences. North Carolina State University. Publ. HIL8513. http://www.ces.ncsu.edu/depts/hort/hil/hil-8513.html

Mackin, Jeanne. 1993. Cornell Book of Herbs and Edible Flowers. Cornell Cooperative Extension. 132 pages.

McCollum, T.G. 2004. Squash. The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks. Agriculture Handbook 66. USDA/ARS. Revised edition. http://www.ba.ars.usda.gov/hb66/129squash.pdf

Villalta, A.M., M. Ergun, A.D. Berry, N. Shaw and S.A. Sargent. 2004. Quality Changes of Yellow Summer Squash Blossoms (Cucurbita pepo) During Storage. Proc. 2004 International Symposium on Protected Culture in a Mild-Winter Climate. Intl. Soc. For Hort. Sci. (In press).