An increase in production is required to keep cultivation of cut amaryllis profitable. Wageningen UR Greenhouse Horticulture and the Improvement Centre in Bleiswijk are to start a three-year study into the effect on production of reduced screening in combination with misting.
Picture: Amaryllis Mont Blanc
Production of amaryllis currently amounts to 45 flower stems per m2 from 27 bulbs per m2. Some bulbs yield three stems and it is therefore expected that it should be possible to raise production to 75 stems per m2. A first requirement for achieving such a production increase is the formation of sufficient flower stem buds. And these buds should then develop into harvestable flowers.
Earlier research has shown that an increased soil temperature, and thus a higher bulb temperature, results in the formation of more leaves and flower stem buds. Part of these buds, however, dry out before they can grow out. This is possibly caused by a deficiency of assimilates. If that would be the case, more assimilates should reach the bulb. A higher photosynthesis is therefore required.
Experience, however, learns that amaryllis may at high radiation and low air humidity suffer from leaf scorching. To avoid this, cut amaryllis crops are in summer often screened.
Misting instead of screening
“We are now going to investigate whether the screen can be kept open longer by misting,” explains researcher Arca Kromwijk. “In other crops it has been found that higher air humidity reduces the negative effects of too much light and that more growth can be achieved. A condition for more growth is that the CO2 concentration must be kept up.”
The study will be taking three years and has been set up in one section at commercial scale in the Improvement Centre. The study will be conducted with the cultivars Red Lion (a frequently grown red cultivar) and Mont Blanc (a white cultivar easily suffering from bud drying). Amaryllis will be grown on two substrates, i.e., perlite and clay granules. The project is financed by the Product Board for Horticulture and by ‘Working together on Capabilities’, a ‘Pieken in the Delta’ project of the Ministry of Economic Affairs and the province South Holland.