Research Matters - Controlling plant height

Nowadays, there is considerable interest in controlling plant height without chemicals. The experiments described below investigated the effects and interactions of forcing air over plants and of water stress.

Plants of Impatiens walleriana 'Dezire' and of Petunia (approx equal to) hybrid 'Tidal Wave' were raised from seed and then grown on ebb-and-flood benches in a greenhouse at a temperature setting of 15 degsC, venting at 20 degsC.

In experiments starting in either April or July, irrigation was supplied when the weight of the plant with its pot and peat compost had fallen to either 25 per cent (control) or 45 per cent (stressed) of its initial weight.

The plants were also subjected to air velocities ranging from 0.1 to 4.5 metres per second, generated by fans with horizontal airflow. Velocities above 0.1 metres per second were given for five in every 15 minutes throughout the day.

Plant height was reduced in both species by air velocities of 4.5 metres per second, although the effect was greatest on water-stressed plants of Petunia in April and on non-stressed plants in July.

Water stress tended to reduce the height and fresh weight of Impatiens plants, although the effect was not significant. With Petunia, however, water stress reduced both height and plant fresh weight.

Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick

The Influence of Water Stress and Air Velocity on Growth of Impatiens Walleriana and Petunia x Hybrid by Andersson (2011).

Scientia Horticulturae 128 (2): 146-151. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at

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