RESEARCH carried out for the Consumers' Association revealed that 31 per cent of visitors to garden centres choose a plant by looking at its label. Another 21 per cent look up plants in books or magazines before they decide to buy. About the same number feel they are sufficiently knowledgeable to choose for themselves. Only 6 per cent of garden centre users thought it worthwhile going to the staff for advice. That will come as a surprise to no one. The research provided the impetus for the CA's Which Plant? computer program which is gradually being installed in garden centres. It is a simple touch-screen program designed to help gardeners choose the right plant for their needs by answering a series of questions. Don't be bossed by it though. Plants have more tricks than even the CA can think of.