Control of Growth and Flowering in Two Western Australian Species of Pimelea

Abstract

Pimelea ferruginea and P. rosea both show an obligate requirement for exposure to mean temperatures below 15°C for more than 5 weeks for induction of flowering. Subsequently, floral primordia develop slowly in these cool conditions or rapidly if the average temperature is raised to 21°C. Plants held at 21°C or warmer remained vegetative for over 1 year. P. rosea was found to be daylength neutral, whereas flowering of P. ferruginea was enhanced, slightly, by a short day photoperiod of 10 h. Plant height was greater for both species in long days. Benzylaminopurine (BA) was effective for increasing branching. Gibberellin A₃ (GA₃) and paclobutrazol were effective in controlling plant height in P. ferruginea. Flower life was not altered by application of silver thiosulfate and BA, and was greatest when plants were grown in high photosynthetic photon flux density and at lower temperatures (15/ 10°C v. 24/19°C).