Writing in Gardeners' World, the TV gardener quoted critics as saying gardeners were "squandering irreplaceable peat bogs," filling the air with noxious chemicals" and "wasting precious water".
But Titchmarsh supported conventional gardeners: "We might use Roundup to clear a patch of ground which will be used to grow organic vegetables or a wild flower meadow. We might also occasionally feel that we have to take drastic action against a pest infestation," he said.
He said he occasionally had "recourse to Roundup" when his bad back stopped him digging. He also sometimes used peat-based multipurpose composts, which "are useful for container-grown plants", although he would use peat-free when the perfect one had been developed, he added. He had not used pesticides for 10 years, he stressed.
In response, garden writer Peter Seabrook said: "For too long the conventional gardener has been ignored. Those with a high profile in the gardening media have a responsibility to give viewers and readers the options of conventional and organic and then it's up to them to decide. To preach one or the other can't be right."