Postharvest Treatment of Gardenia

Please find images and charts here.

Gardenia, also known as cape-jasmine, is a common evergreen woody species, widely grown in the United States in the South and on the West Coast. It has become a popular cut flower for its lush, fragrant, white or creamy flowers, which are available from late spring to midsummer. Once cut, the flowers may last for 1-3 days under most circumstances; however, their vase life can be doubled if properly handled.

For extended longevity, stems should be harvested by cutting with sharp cutters. Avoid pulling stems as the uneven wounding can shorten the vase life. Harvest buds in the morning and open flowers in the afternoon. Studies conducted at North Carolina State University (NCSU) have shown that for proper bud opening and longer vase life, stems should be harvested when petals have started to unfold (see photo below) as many stems harvested at bud stage failed to open further in vases. On the other hand, harvesting too late, when flowers are fully open, should also be avoided as the petals bruise easily and turn brown during handling.

Limited information is available on gardenia postharvest handling. Therefore, experiments were conducted at NCSU to determine ethylene sensitivity, and effect of anti-ethylene agents (STS and 1-MCP), and find the best commercial preservative for gardenias. Stems harvested in the morning at a commercial flower farm were packed dry in a floral box and transported to NCSU within 24 hours of harvest. Upon arrival, stems were treated with either 1-MCP (Ethylbloc), STS (Chrysal AVB), or water (control) for 4 hours and then exposed to 0, 0.1 and 1.0 ppm ethylene for 20 hours. In the second experiment, stems were placed in Floralife Clear Professional for 48 hours and then moved to water, or in Floralife Crystal Clear, Floralife Rose Food liquid or water (control) continuously. Stems were observed daily and were considered dead when more than 50% of the petals were wilted, faded, or necrotic, the stems bent or buds failed to open.

Gardenia was not sensitive to ethylene when exposed to 1.0 ppm for 20 hours as all treatments had similar vase life, which averaged 7.0 days (Table 1; Fig. 1). Major reasons flowers were terminated included petal wilting, fading and necrosis, with only a few showing bent neck. Stems placed in STS had no bent neck, and those in water and 1-MCP had 11 and 13% bent neck, respectively. While the anti-ethylene agents had no effect on vase life, 66% of buds placed in STS opened completely compared with only 38 and 20% buds opened completely in water and 1-MCP, respectively (Fig. 2).

In the preservatives study, placing stems in Floralife Rose Food extended vase life by 2 days as compared with water, and more flowers opened (93%) as compared with other preservatives and control (water), while Floralife Crystal Clear extended vase life by 0.8 days (Table 2;  Fig. 3). However, Floralife Clear Professional had similar vase life as water (control). Gardenia did not benefit from the use of Floralife Clear Professional. Preservatives had no statistical effect on petal wilting, fading or bent neck, although Floralife Rose Food may have reduced bent neck and petal wilting. All the preservatives had more necrotic petals as compared with water only (control), but that could be due to the flowers lasting longer (Fig. 4). Preservatives significantly improved flower bud opening and stems placed in Floralife Rose Food had very attractive, large sized, fully opened blooms, with Floralife Crystal Clear being the second most effective preservative (Fig. 4).

In summary, gardenia growers should pay attention to the harvesting process and the harvesters should be properly trained for harvesting the stems at proper stage when petals have started unfolding. It is good news that gardenias are not ethylene sensitive. Gardenia stems do best when placed in Floralife Rose Food as compared to the other preservatives tested.

The authors gratefully acknowledge the Kitayama brothers for providing gardenia stems and Floralife for providing preservatives for the studies.