Effectiveness of Ethephon Treatments in Reducing Seed Set in Kalmia latifolia L.

Abstract

Nursery production of Mountain Laurel (Kalmia latifolia L.) often involves manual disbudding or deadheading flower clusters immediately after flowering, to stimulate the formation of one or several new shoots. Experiments were initiated on populations of K. latifolia `Angel' (41 plants), `Snowdrift' (17 plants), and `Hoffman's Pink' (37 plants) to test the effectiveness of single applications of 0 (water control), 500, 1000, and 2000 ppm ethephon in reducing seed set and stimulating new shoot formation. Ethephon was applied on 9 June 1995 when an average of 52.9%, 53.4%, and 27.3% of the flowers were open in each flowering cluster of `Angel', `Snowdrift', and `Hoffman's Pink', respectively. On 17 to 19 July 1995, data were collected for numbers of green seed capsules per flower cluster and the number of new shoots per plant. One way analysis of variance showed the treatments had highly significant effects on seed capsule numbers per flower cluster and in stimulating the production of new shoots per plant in the three cultivars. The average number of green capsules per flower cluster and new shoots per plant for each cultivar treated with 2000 ppm ethephon were: 2.2 capsules and 57.2 shoots in `Angel', 1.1 capsule and 40 shoots in `Snowdrift', and 6.6 capsules and 39.3 shoots in `Hoffman's Pink'. In contrast, the controls had 20.1 capsules and 2.8 shoots in `Angel', 22.9 capsules and 8 shoots in `Snowdrift', and 27.3 capsules and 2 shoots in `Hoffman's Pink'.