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Abstract: The aim with this thesis is to make a comparison between forcing tulips in a hydroponic system and the forcing off tulips that have been planted in soil. The results are mostly based on interviews with six Dutch and one Swedish tulip forcer and the managing director at the Horticultural Research Centre, Proeftuin Zwaagdijke, in the Netherlands. There are benefits and disadvantages with both methods. Tulip bulbs planted in soil seem to get a brighter colour after forcing, compared with those forced "in water". Tulips forced in soil also seem to have more problems with cellblast. The latter problem differs between the varieties, such as 'Monte Carlo' which is the variety with the largest problems. Hydroponical forcing results in both more even growth and quality. Its of great importance to keep a high level of hygiene while working with a hydroponical system. For that reason it is not recommended to combine hydroponical forcing and forcing in soil in the same greenhouse. When using a system with circulating nutrient system it is important to clean the water by using a sandfilter and UV- lamps. The plastic forcing trays have to be cleaned by using Hydrogen Peroxide (H2O2). Tulips which are forced in water have a shorter cooling period compared with the other category which needs more cooling space. Pre-cooled bulbs can be bought to save further more space. It is therefore possible to use the same forcing trays 2-3 times during the same season. When forcing the tulips in water, the air temperature can be kept 1-2°C lower then normal, which saves energy. There are less problems with diseases as Fusarium in a hydroponical system and it is easier to use fungicides. The opinion that some varieties cant be used in a hydroponic system is dominating among the respondents, but for some varieties with heavy foliage for e.g. 'Christmas Marvel' and 'Yokohama' there are advantages. One respondent (Arjen Leek) on the other hand pointed out that an ebb and flow system had no limits in this aspect. One problem that all forcers agreed with, was that bulbs bigger than 14-15 cm in circumference can't be used in hydroponic systems. Big bulbs can get problems with Pythium and to much growth. Root growth can be a problem when forcing in hydroponic systems. The long roots can affect the water quality negatively and they can also complicate the harvesting. Short roots on the other hand have a lower uptake of nutrients. The main reason why many Dutch growers have changed to hydroponic systems is the environmental problem with using peat as a substrate. Tulips that are forced in hydroponic systems and soil have the same shelf life. Tulips forced in hydroponic systems do grow little more in the vase.