Herbert Whitley, a fellow of the RHS and eccentric recluse, created Paignton Zoo Environmental Park in 1923.
According to plants and gardens curator Kevin Frediani: "He enjoyed the challenge of breeding the colour blue in everything from poultry to plants because it is difficult.
"Now we want to bring back as many of his cultivars as we can – and we are asking the trade and private growers to help us find them."
Whitley’s Primley Botanic Nursery launched a number of cultivars named ‘Primley Blue’ including mallow, rosemary and hebe.
"We have Primley Blue rosemary in our economic garden. But we think there were many more. "
Frediani added. "I’d be very excited to get my hands on an old nursery catalogue and read about what was grown."
The appeal coincides with this year’s Plant Conservation Day on Wednesday 18 May.