Flowering of Watsonia laccata as influenced by corm storage and forcing temperatures

• Published in: South African journal of botany 2011-08, Vol.77 (3), p.631-637
• Main Authors: Suh, J.K., Kim, J.H., Lee, A.K., Roh, M.S.
• Format: Article
• Language: English
• Subjects: Controlled flowering; Corms; Dormancy; florets; flowering; greenhouses; Leaf-tip burn symptoms; leaves; New floral crops; night temperature; rain; Watsonia; Watsonia laccata
• ISSN: 0254-6299; 1727-9321
• DOI: 10.1016/j.sajb.2010.12.007

The genus Watsonia, belonging to the family Iridaceae, is comprised of about 50 species including W. laccata (Jacquin) Ker Gawler that flowers from September to November following low temperature and winter rainfall. Therefore, we hypothesized that flowering would be favored by forcing at low greenhouse temperatures. Using clonal W. laccata corms, four experiments were designed to investigate the effect of temperatures during corm storage, forcing, and their interaction on growth and flowering. Corm formation is favored by growing plants at 18°–20°/15°–17 °C and 21°–23°/18°–20 °C, day/night temperatures. Flowering was earliest with corms produced at 24°–26°/18°–20 °C and forced at 18°–20/15°–17 °C, and was significantly delayed when forced at 27°–29°/24°–26 °C. Flowering was, however, favored by 2 or 4 weeks of high temperatures (27°–29°/24°–26 °C) prior to forcing at low temperatures (18°–20°/15°–17 °C). The number of florets was not significantly affected by corm storage, forcing temperatures, or their interaction, although forcing at high temperatures tends to reduce the floret number. Burn symptom at the tips of leaves was frequently observed, and further studies are required to understand the cause of the tip burn and how to correct the symptom. ► Using clonal W. laccata corms, the effect of temperatures during corm storage, forcing, and their interaction on growth and flowering were investigated. ► Corm formation is favored at low temperatures, resulting from an early initiation of daughter corms following flowering. ► Flowering of W. laccata is accelerated and promoted by forcing at low temperatures around 18 ° – 20 ° /15 ° – 17 °C for 8 weeks followed by 2 to 4 weeks of 27 ° – 29 ° /24 ° – 26 °C. ► No malformation of florets was found when plants were forced at high temperatures, and the length of scape and inflorescence was not affected significantly by forcing temperature.