Project founder Clive Farrell has told at least three garden designers they will not be fully paid until more funding comes on board for the £27m Hertfordshire attraction.
Actress Emilia Fox opened the 11ha site in June, but the expected 200,000 visitors failed to arrive.
Twelve designers won bursaries of £25,000 each to build gardens. But Paul Dracott, Tony Heywood and Fiona Heron have not been fully paid. Delivery partner TJM Associates, which ran the annual 120,000-visitor Westonbirt garden show in the early 2000s, said it is also owed money.
TJM partner Therese Lang said: "It won't happen next year. There is not enough money to do the gardens via the bursary scheme."
Dracott, who is owed more than £20,000, is considering legal action. He said: "I am owed a considerable amount for my garden."
Farrell said funding the indoor butterfly house phase two would drive visitor numbers, but refused to say what attendance figures were. HW reported just 3,000 visited in the first month. He said: "I am struggling with dozens of invoices at the moment. It's a dreadful situation."
The site closes for the winter on 4 October.
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