Woolworths has debts if £385m but is trading on while its administrators look for buyers.
Suppliers to the 800-store high street chain include AE Roberts, Mr Fothergills, Scotts, De Ree and Porters Horticultural.
They have orders ready to be delivered in January but fear they no longer have a buyer.
AE Roberts MD John Gwynn, who supplies trees, fruit bushes, shrubs and climbers, said: "We can't put the crop we're growing for them on hold so we're working extremely hard to sell elsewhere."
For more reactions see the next edition of Horticulture Week, 5 December.