He has been appointed to chair an RHS discussion group to develop a "road map" to help amateur plant breeders to get the hundreds of new plants bred annually to market.
The RHS vice-president said: "If someone big comes along and offers £100 or £500 or £1,000 for a plant, don't be taken in. Your plant might be worth more."
The steering group will meet growers, breeders, agents and nurserymen. It met on 6 November 2014 at Wisley in an event organised by RHS plant committee co-ordinator Lesley Whayman and vice chair of the RHS herbaceous plant committee Sarah Cook.
Thompson & Morgan offers a £500 "lump sum" when a submitted new plant goes on sale, though "outstanding or rare new products could receive more".
New product development manager Michael Perry said: "In most cases the product is not ready to go. When a customer finds something in their garden and thinks it's different, it can take 10-15 years to make it saleable.
"Everyone has different methods. People can choose to come to you. I don't know what other deals are out there but we offer £500. We're trying to help the home breeder. We don't want just small specialist things but things able to sell 100,000."
Plants for Europe owner Graham Spencer said high plant breeders' rights examination fees mean some companies are skimping on them. A conservative trend means variations rather than unusual plants are introduced.
Fairweather's owner Patrick Fairweather said it is becoming more difficult to find exclusive new plants as a medium-sized grower.