Just 20 per cent say they want to leave.
Reasons nurseries gave for staying are 70 years of peace in Europe, easier trade with Europe and uncertainty about leaving.
Many growers said they had received too little information and what they had heard was conflicting.
Those for Brexit at the referendum in June said immigration and the belief that Britain can manage on its own as it did before 1973 were among reasons for leaving.
Growers at the show said that retail sales had yet to take off. They said they had sold in but poor weather meant consumers had yet to get into their gardens. Many said Easter would come too soon and they wanted a fixed date for the festival later in April.
Concerns included National Living Wage, with growers accepting the hike to £7.20/hour from April but believing as it reaches £9/hour by 2020 then issues caused by differentials will cause financial problems.
See more in Horticulture Week 18 March.