Speaking in his capacity as the new president of Plant Heritage, Titchmarsh told HW that the industry should help revive good garden plants. "There is a great temptation in the trade to keep bringing new varieties out," he said.
"Yes, we need them to refresh the trade and it is good PR, but we shouldn't let good old ones slip away. We should be looking for all-round performance and not just new for the sake of new.
"So I think we can be more aware of what we need. There is a danger of bringing in plants for the sake of them being new, when they haven't been tested as thoroughly as perhaps they should have been."
Opening the charity's Hampton Court marquee, he warned the audience that children were "growing up in danger of not knowing how nature works," arguing plant heritage is a pivotal facet of gardening.
He added: "It's up to us to keep going all those great varieties for coming generations. Gardeners are at the sharp end of conservation. If you can hand over your bit of earth in a similar or better state to that in which you found it then you have done your bit. Plant Heritage epitomises that."
But garden writer Peter Seabrook defended the industry, arguing that some old varieties slip away because they have been superseded. "Take for example tomatoes," he explained. "Most of the heritage cultivars are not worth eating, and those that are either have poor yields or are susceptible to disease.
"This year I am trialling 10 new tomatoes, few of them will be available in 10 years' time. It was, however, only by trialling Tomato 'Red Alert' in 1980 that I found the earliest, good-flavoured, bush tomato that is still listed today. On current showing some of the Vegetalis novelties will be an improvement on Red Alert, but then in 10 years we will have even better blight-resistant cultivars.
"There are not enough garden communicators doing their homework and keeping up to date with the steady advancements being made. Too many take the easy option and live in the past."