Verbetering trekresultaten van vroege trek bij Viburnum opulus "Roseum" (sneeuwbal): Onderzoek naar bloemknopontwikkeling en koubehoefte voor rustdoorbreking

Abstract In the early forcing of Viburnum opulus 'Roseum' (Snowball), results are sometimes disappointing: only a few or sometimes none of the buds develop into inflorescences, or so-called 'grass balls' emerge. At the request of the growers and with funding from the Horticulture Board, Wageningen UR Greenhouse Horticulture, explored flower bud development in Viburnum. The starting time of flower bud development varies. An early start leads to a high number of flower buds per branch. After the development of the flower buds, they go into winter dormancy. Problems with development to inflorescences are due to lack of cold for breaking bud dormancy. Viburnum needs 900 hours of 2 to 8 oC to break bud dormancy. ‘Grass Balls’ are caused by incomplete flower bud development. If the flowers in an inflorescence are not or incompletely developed, small green leaves grow from the inflorescence