Pinching, Bulking Duration, and Plant Growth Retardant Effects on Growth and Flowering of Greenhouse-grown Achillea בCoronation Gold’ and Coreopsis verticillata ‘Moonbeam’

Abstract

Achillea בCoronation Gold’ (‘Coronation Gold’ achillea) and Coreopsis verticillata L. ‘Moonbeam’ (‘Moonbeam’ coreopsis) are popular herbaceous perennials that are widely grown under nursery and greenhouse conditions. Herbaceous perennials are considered to be of high quality if they are well branched and full in appearance, with multiple flowers that open simultaneously. A balance between container size and plant size is also necessary to achieve high perceived quality. One study was conducted to determine the effects of a soft pinch on the offset from propagation and the plant growth retardant, daminozide (B-Nine), on growth and flowering of ‘Coronation Gold’ achillea. Pinching decreased inflorescence stem length by 6.4%, but increased the number of flowering offsets and total offsets by 33.3% and 9.1%, respectively. Daminozide decreased inflorescence stem length and the number of flowering offsets by 7.9% and 40%, respectively, but increased the time to first open inflorescence and the number of non-flowering offsets by 6 days and 28.6%, respectively. Pinching at 7 weeks resulted in the highest number of flowering, non-flowering, and total offsets and the lowest days to flower and intermediate flower stem length. Pinching at 7 weeks after potting resulted in the most improvements in plant qualities related to marketability with the fewest drawbacks. Another study was conducted to determine the effects of bulking duration and daminozide on growth and flowering of ‘Coronation Gold’ achillea and ‘Moonbeam’ coreopsis. Increasing bulking duration increased flower and flower bud number of both plants for the early fall potting date, but only increased flower and flower bud number of ‘Coronation Gold’ achillea for the late fall potting date. There were much more flowers and flower buds for the early potting date than the late potting date over all bulking durations for both plants. Daminozide suppressed ‘Moonbeam’ coreopsis plant height at first open flower by 31-49% and suppressed ‘Coronation Gold’ achillea first open flower stem height by 20-43%, but increased the time to first open flower for both plants. Daminozide also increased flower and flower bud number of coreopsis by 13% over all plants, but decreased flower and flower bud number of achillea slightly.