The broadcaster, 71, who joined in 2003, will leave the horticulture programme at the end of the current series later this year.
He said: “I have decided that the current series of Gardeners’ World is to be my last.
“I began hosting the programme 23 years ago, first at Berryfields and for the past 16 years here in my own garden, Longmeadow.
“Throughout that time – and around 700 programmes – I have had the privilege of sharing my own abiding passion for gardens and gardening with an equally passionate, and often equally knowledgeable, audience.
“That connection with millions, not just in Britain but across the world, who share a love of gardens, plants and the natural world is something I have always treasured and which I increasingly believe to be at the heart of a life well lived.
“I have also always relished the craft of programme making and to do so, week in week out, as part of a superlative BBC team has been a deeply rewarding experience. But now is the right time for a change.
“I look forward to continuing to work with and for the BBC on other projects, as well as following new avenues. There are more books to write, more programmes to make.
“And of course, I will still be gardening, dog by side, here at Longmeadow.”
