Buckland said: "Powderham has huge interest this year with 150 exhibitors wanting to come, more than half as many again as 2014."
Powderham (1-2 May) and Bowood (5-6 June) will feature nurseries such as Hardy's Cottage Garden Plants, Pennards and Whetman Pinks. The speakers lined up at Bowood include Anne Swithinbank, Roy Lancaster, Jim Buttress and James Wong, with Christine Walkden, Bob Flowerdew and Buttress at Powderham.
Buckland said the shows are ideal for smaller nurseries because they can grow volume blocks of plants and offer supermarket-style three-for-two deals. They operate like pop-up shops and offer many plants not available in garden centres.
The shows have a "horticultural heart but a festival vibe", he added. "Glamping compared to camping."
A "couple more" shows under the same brand are planned in stately home grounds or city centres. He said his typical visitor is "anyone who pays council tax".
Entrance at Bowood will be £10 in advance and Powderham £7.50 on the door.