Janet C. Cole, Department of Horticulture and Landscape Architecture, OSU, Stillwater, OK and Diane E. Dunn, Greenleaf Nursery Co. Park Hill, OK
Introduction: This study was the second of a three-part study to determine if BA would increase the offshoots of three hostas cultivars. The current standard nursery practice is to purchase 95% of hostas for production, obtaining the other 5% by dividing stock plants in the field. Increasing offshoots with BA would provide more divisions for planting and decrease production costs. The cultivars, 'Francee', 'Patriot', and 'Wide Brim' were selected based on their purchase price from suppliers. Application of BA to 'Francee' (2,4,5) and 'Wide Brim' (3) has been shown to increase offshoots.
Materials and Methods: Dormant liners of 'Francee', 'Wide Brim', and 'Patriot' hosta were planted on June 18, 2001 into 19 L (5 gallon) containers containing a 6:1 pine bark:sand media with 6.9 kg/m3 (12 lbs/yd3) 22N-2.1P-8.3 controlled release fertilizer (22-5-10 Osmocote, The Scotts Company, Marysville, OH) incorporated. Liners were bareroot divisions received June 10, 2001 from Yoder Enterprises and kept in a cooler at 1oC (340 F) until planting. Number of offshoots per division was counted planting. Plants in containers were placed on gravel nursery beds in full sun.
On July 18, 2001 single foliar sprays of 0, 1, 2, 3, or 4 g/L (0, 1,000, 2,000, 3,000, or 4,000 ppm) benzylaminopurine (BA) were applied to the plants to runoff. The BA was dissolved in 12 ml (0.4 oz) of hydrochloric acid, then the BA-acid mixture was diluted with 236 ml (8 oz) of water. The 0% BA (control) treatment consisted of 12 ml (0.4 oz) hydrochloric acid/236 ml (8 oz) water. Plants were approximately 12 cm (4.7 in) tall with 4 to 5 leaves unfurled at time of application. The air temperature at application was 29o C (840 F).
Plants receiving the late BA application were sprayed September 18, 2001. The air temperature was 31o C (88o F). The plants were approximately 15 cm (6 in) tall and leaves were completely unfurled.
Number of offsets was counted January 16, 2002 after new offsets began to emerge. The percentage increase in offsets was calculated by the equation: ((Final number of offsets-Initial number of offsets)/Initial number of offsets)*100.
Plants were arranged in a split split plot design with cultivar as the main plot, spray time as the subplot and BA concentration as the sub subplot. Data were analyzed using a general linear models procedure (SAS Institute, Cary, NC).
Results: Cultivar, application date and concentration interacted for the percentage increase in offsets. 'Francee' plants that received a late BA application produced the greatest increase in offsets compared to other cultivars and compared to 'Francee' receiving BA at the early application date. In contrast, 'Wide Brim' plants receiving an early application of BA generally had a greater increase in offsets than those receiving an early BA application. 'Patriot' offset formation was about the same regardless of whether an early or late BA application was used.
Discussion: The 3 g/L (3,000 ppm) and the 4 g/L (4,000 ppm) BA bleached and burned the foliage. Similar damage was reported by Findley, et al (1). New leaves on the 3 g/L (3,000 ppm) and 4 g/L (4,000 ppm) treatments were rosetted, straplike, and often twisted. This was especially true for the 'Wide Brim'. While more offsets were produced by some treatments, the offsets were too small at the time final data were collected to be readily divided.
Growers have noted that stressed hosta plants produce more offsets compared to nonstressed plants (3). The hostas in this study were extremely stressed due to growing in the full sun and phytotoxicity that occurred on the leaves.
Literature Cited:
1. Findley, D.A., G.J. Keever, and C.H. Gilliam. 1994. BA-induced offset formation in hosta. Southern Nursery Assn. Res. Conf. 39:33-34.
2. Garner, J.M., G.J. Keever, Eakes, D.J., and J. R. Kesler. 1996 Sequential BA applications enhance offset formation of hosta. Southern Nursery Assn. Res. Conf. 41:48-50.
3. Ruter, J.M. 2001 Container design influences offset production of hostas. Southern Nursery Assn. Res. Conf. 45:87-88.
4. Schultz, H.C., G.J. Keever, J.R. Kessler, R.R. Dute, and J.W. Olive. 1998 Root mass and BA affect offset formation in hosta. Southern Nursery Assn. Res. Conf. 43:300-302.
5. Schultz, H.C., G.J. Keever, J.R. Kessler, and R.R. Dute. 2001. BA does not reduce detrimental effects of high nighttime temperature on offset formation in hosta. J. Environ. Hort. 19:29-32.