ISHS Acta Horticulturae 227: International Symposium on Vegetative Propagation of Woody Species
POTENTIAL FOR IMPROVED PROPAGATION BY LEAFY CUTTINGS THROUGH THE USE OF FOG |
| Authors: | R.S. Harrison-Murray, B.H. Howard, R. Thompson |
| Abstract:
In the 1950s the advent of mist broadened the range of subjects that could successfully be propagated from cuttings on a commercial scale. It permitted relatively high light intensities to be used before water stress or excessively high temperature started to limit rooting. Surrounding cuttings in a cloud of water droplets small enough to remain suspended in the air, i.e. 'fog', is even more effective as a means of limiting water stress and therefore further broadens the range of subjects that can be propagated from leafy cuttings. This paper summarises experience with a ventilated fog system based on a modified Agritech machine which has a sufficient output of fog to maintain high humidity even during forced ventilation. In addition to periods of ventilation (when air temperature exceeded 27.5°C) the fogger operated for 2 min every 15 min during daylight hours. This maintained visible fog at all times. In preliminary comparisons most of the subjects tested, including M.9 and MM.111 apple, Rubus idaeus, Acer platanoides, Tilia cordata and Viburnum carlesii, rooted in greater numbers in fog than in mist. In more critical comparisons using polythene-enclosed mist at matched irradiance some substantial responses remained; 80% of Acer platanoides 'Crimson King' cuttings in fog rooted compared with 47% in polythene-enclosed mist. In this subject rooting was achieved in 3–4 weeks but in others, such as Rubus idaeus, the benefit of fog seemed to be to maintain cuttings in a healthy condition long enough for rooting to occur eventually. Rooting was depressed in Euonymus fortunei 'Silver Queen' and Cytisus 'Burkwoodii' when propagated in fog compared to open mist. | |
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