Kalanchoe can grow at low phosphate levels but phosphate is not an effective instrument for suppressing longitudinal growth. Shorter plants have a poorer quality because the plants have lower and thinner leaves. This was found in research by Wageningen UR Greenhouse Horticulture.
The use of growth regulators in Kalanchoe cultivation has decreased in recent years with the arrival of new, more compact cultivars and better insight into the time of application of growth regulators. Nevertheless, cultivation of a compact Kalanchoe still requires suppression of longitudinal growth.
Lowering phosphate levels for suppressing longitudinal growth gave good results in the cultivation of annual summer flowering species. Wageningen UR Greenhouse Horticulture has investigated whether lower phosphate levels would also offer possibilities for suppressing longitudinal growth of Kalanchoe.
Quality loss
Two experiments with the phosphate level as variable were carried out in 2009. The first experiment started in week 10 and the second in week 29. The experiments were carried out with the cultivars ‘Tenorio’ and ‘Mie’ and included combinations of various levels of basic dressing and top dressing. The effects on longitudinal growth, number of shoots, and fresh weight of the flowers were recorded.
These experiments showed that plants receiving the lowest amount of phosphate by means of top dressing remained shortest and had the lowest number of shoots as well as lowest fresh weight. Differences in basic dressing had little effect.
The researchers conclude that phosphate deficiency does also suppress longitudinal growth in kalanchoe. This, however, has a negative effect on quality. This means that lower phosphate dressings are not a suitable alternative for chemical growth inhibition.
This research was financed by the Product Board for Horticulture.