West Sussex-based Allwoods owner David James said: "English Heritage contacted us because we grow a unique range of carnations and they wanted varieties from the 17th century."
He said older carnations are making a comeback: "I think people with old houses and general interest in that style of gardening are looking for old, unusual varieties."
Southview Nurseries owner Mark Trenear said he is to send rare Dianthus caryophyllus plants, collected as seed by Sherbourne Castle's head gardener Tim Stiles, to English Heritage.
English Heritage head of gardens and landscape John Watkins said by 1600 there were 60 carnation varieties stemming from Morocco: "The 16th-century garden was highly sensual. Perfume was an essential part of the garden experience and the clove-scented carnation was an important high-status plant, crucial in the heady summer cocktail of strawberries, roses, stocks, peonies and pinks."
English Heritage is looking for examples of true species, strongly spice-scented, with a flowering period of five to six weeks in June and July and very feathered petals.
Kenilworth Castle Garden will open to the public in May 2009. The garden was created by Elizabeth I's favourite, Robert Dudley, who hoped to persuade her to get married.
- Call English Heritage on 0870 333 1181 or email firstname.lastname@example.org.