The sale of garden plants in supermarkets leads to a "diminution of choice" with lots of the same blooms produced as cheaply as possible, Monty Don has said.
The TV gardener compared the mass production of plants such as fruit trees for supermarkets with "vast" suppliers of food, and championed independent nurseries which could give gardeners advice and support.
Speaking to BBC Radio 4's You and Yours in his garden at Longmeadow, Herefordshire where Gardener's World is filmed, Mr Don said: "You have these vast wholesale nurseries now supplying supermarkets and actually that's a diminution of choice, that's bad, because all you get it's rather like vast suppliers supplying food."
"You get lots and lots of exactly the same thing, mass produced to be as cheap as possible."
He said he was a "huge fan" of independent nurseries, which could give people "great hope and assistance" with their gardens.
"That is where you get the expertise, that is where you will find people who have devoted their lives to growing something and know far more about it than I do or anyone else on television, because their life on one thing, so they will grow geraniums or they will grow fruit trees and they will really know about it," he said.
He also recommended all gardens should have a rose, suggesting Alba roses "because the scent is fantastic and they're as tough as old boots, you can't go wrong".
In the interview, the Gardener's World presenter admitted he had not been a fan of the programme when he was younger, thinking it was full of "middle-aged people in cardigans" who were not speaking to him.
Responding to the comments, Martin Simmons, Horticultural Trades Association director of operations said: "People often make impulse purchases of plants in supermarkets and if this then encourages them to buy more plants then this is good for the industry and helps to grow the market.
"Buying a plant in a supermarket may be the first step for some consumers, particularly younger ones, and if this then gets their interest they will naturally seek out garden centres and retail nurseries as a follow-on benefiting from the great customer service, knowledge and advice they receive in these destinations."
An Asda spokesman said: "At Asda we work with a network of expert growers and nurseries that allows us to offer fantastic quality and value plants to our green-fingered customers."
A Waitrose spokesman said: "Gardening is the second most popular pastime for Waitrose customers after cooking, so we take the quality of our offer seriously.
"Our plants are supplied by two nurseries that are long-established and extremely reputable and our growers only supply garden centres, not other supermarkets."
And a spokesman for Sainsbury's said: "We have longstanding relationships with our suppliers. Many are second and third generation family businesses, who also grow plants for their own nurseries and garden centres.
"We have limited space in our stores, but always aim to give customers as much choice as we can, and for the best possible value."
:: BBC Radio 4's You and Yours programme featuring the interview with Monty Don airs on Tuesday June 6 at 12.15pm.