Influence of Harvest Date and 2C Storage on Floral Development of Dutch-grown Astilbe

Dutch-grown 'Deutschland', 'Fanal', and 'Rheinland' Astilbe, harvested 1 Nov. 1992 and shipped to the United States, were dissected to determine the stage of floral development after 0, 2, 4, 6, 8, 10, 12, or 15 weeks of 2C storage. Astilbe crowns were also planted after 15 weeks of 2C storage and floral development was determined after 1, 2, or 3 weeks of greenhouse forcing. On arrival, multiflower inflorescences were clearly visible. A pattern of abortion and reinitiation occurred during 2C storage. Floral development was markedly repressed when ecodormancy was imposed, but development resumed during greenhouse forcing. During the observational period, floral organ numbers were variable, and morphological abnormalities were observed. In a second experiment, physiological maturity of the crowns was evaluated by harvesting crowns of 'Bumalda', 'Europa', 'Federsee', and 'Rheinland' on 15 Sept., 1 Oct., 15 Oct., 1 Nov., and 15 Nov. in The Netherlands. Optimal harvest period was from 1 Oct. to 1 Nov., depending on the cultivar. Crowns harvested before this period were physiologically immature. Crowns harvested during the 4-week window produced the highest overall plant quality and performed as physiologically mature crowns. Astilbe crowns harvested after the 4-week window produced plants with lower forcing qualities and were determined to be beyond the optimal physiological state for forcing. Professor. Astilbe are field-grown in The Netherlands and are harvested from 1 Oct. to 1 Dec. (T. Ruigrok, personal communication). The decision to harvest the crowns usually depends on seasonal weather conditions. One major problem associated with forcing Astilbe has been flower abortion. Crowns harvested early in the season may not be physiologically mature or may be juvenile in nature. A delayed harvest may result in crowns that are overmature for forcing. Rosa odorata) and mixed hollyhocks (Alcea rosea) to demonstrate the importance of plant maturity for storage life, survival, and subsequent growth. He found that when harvesting was delayed from 24 Sept. to 29 Oct.,