A spokesman said: "Plant-selling retailers should be more aware of their customers' positions. They should inform them there is a restriction, and warn them to be careful with what they buy."
However, an NFU spokesman said: "Warning customers doesn't do anybody any favours, and I would question any retailer who would advise customers not to buy plants and flowers. Retailers need to be more proactive and equip customers with advice on efficient watering. There is a host of simple things that can be done to keep gardens colourful."
The public could use water from the bath or washing up, line pots with moss or water from the base rather than the top of the plant, he said.