Submitted to: Scientific Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 4, 2004
Publication Date: April 5, 2005
Citation: Roh, M.S. 2005. Flowering and inflorescence development of Lachenalia aloides 'Pearsonii' as influenced by bulb storage and forcing temperature. Scientia Hort. 104:305-323. Interpretive Summary: Lachenalia is still considered a new crop due to the limited availability of new hybrids to the industry and lack of information on controlled flowering. Lachenalia 'Pearsonii' was readily available from Israel for past commercial production. To produce a quality plant in many bulbous plants, bulbs should be stored after harvest at optimum temperatures for flower stem and florets to initiate. Upon completion of floret development, bulbs are then cooled at low temperature so that flower stem can elongate and flower. However during these temperature treatments that may last for longer than 6 months, bulbs are sometimes exposed to unfavorable temperatures and quality plants can not be produced. In Lachenalia, optimum temperature for floret initiation and development ranges from 58 - 75F. Once florets are initiated and developed, bulbs are then stored at low temperatures. However, exact low temperature and its duration in relation to quality Lachenalia plant production are not known. To produce compact plants at flowering and to increase post-harvest life and floret numbers, optimum environments must be provided during bulb storage and the greenhouse forcing period. Based on the greenhouse forcing experiment, magnetic resonance imaging and scanning electron microscopy, high quality plants with short leaves, many florets, and short floral stems were produced by storing bulbs at 50 - 58F before potting for 30 days and forcing at 63F, day/58F, night. During bulb storage and early greenhouse growing period, bulbs should not be exposed to high temperatures (86F) to prevent malformation of flowers and the death of flower stems.
Technical Abstract: The effect of bulb storage and forcing temperatures on growth, flowering, and inflorescence development and the death of inflorescence (blast) of Lachenalia aloides Engl., 'Pearsonii' was investigated. Bulb temperature treatments began when about 5 florets were developed. Bulbs were stored at 10o, 12.5o, 15o, 20o, and 25 oC for 15, 30, or 45 days and forced in greenhouses at 17/15 oC and 21/19 oC. Flowering was accelerated, and leaf length and floret number were reduced, when bulbs were stored at 10o, 12.5o, or 15 oC for 45 days compared to storing at 20o or 25 oC. Flowering was further accelerated by forcing at 17o/15oC compared to 21/19 oC (Expt. 1 and 2). When bulbs were stored at 10o, 15o, 20o, or 25 oC for 4 weeks and grown in greenhouses at 17/15 oC, 21/19 oC, 25/23 oC, and 29/27 oC, the incidence of inflorescence blast was increased when bulbs were stored at 10o and 15 oC and forced at 25/23 oC compared to low temperatures (Expt. 3). Bulbs were stored at 10o, 15o, 20o, or 25 oC for 4 weeks and forced in greenhouses maintained at 18/16 oC, 22/20 oC, or 26/24 oC for 12 weeks. During forcing, plants were subjected to constant [18/16 oC - 18/16 oC - 18/16 oC (16 o-16 o-16 o)] or alternating [18/16 oC - 22/20 oC - 22/20 oC (16 o-20 o-16 o)] forcing temperatures at 4-week intervals (Expt. 4). Inflorescence blast occurred when the temperature was 26o/24o during the first 4 weeks after potting of bulbs that were stored at 15oC (83%) and 10oC (50%). Plants from bulbs stored at higher temperatures did not show inflorescence blast. To produce quality plants with short leaves, many florets, and short floral stems (scape plus inflorescence), it is recommended to store bulbs at 10o to 15oC before potting for 30 days and to force at 17/15 oC accelerated flowering. Inflorescence development during bulb storage at 10 oC and inflorescence blast that occurred after only 3 days of 30 oC was demonstrated using scanning electron microscopy and magnetic resonance imaging techniques.