Webbs Garden Centre chief executive Boyd Douglas-Davies said it was wrong to reward customers with giveaways that bore no relation to the garden industry.
"Why are we sending people away from our industry with the awards?" he asked. "The current reward is for a spa treatment. Wouldn't it be better to reward people with a voucher to go and see an inspirational garden?"
But HTA director-general David Gwyther said the scheme was "aimed at people who are more marginal gardeners so we have to talk to them in language they understand". He acknowledged the scheme was new and said the "jury is still out".