Cornwall Council's Morrab Gardens in Penzance has looked again at its "subtropical" label after being hit by frost in 2009.
The local authority's parks department head gardener Stuart Wood said: "We've planted a lot of tender plants at Morrab Gardens over the years. We hit minus five this year, which is very unusual because we're this far south and so close to the sea. But in the past two winters temperatures have dropped and Lampranthus, Euonymus, Agave and bananas have all suffered."
Wood said bananas were recovering and Cordyline and Phoenix palms had narrowly avoided cold damage. He added: "We'll certainly have to be more cautious with some varieties now. We're not going to put all our eggs in one basket like we have been doing."
Cornwall Garden Society representative Giles Clotworthy said: "There has been the temptation to plant more semi-tropical plants because of Cornwall's maritime climate. "Dicksonia tree ferns were very slow to recover after winter 2008 and after being frosted again in 2009 some are beginning to look like they will not survive.
"I think a lot of people are going to become much more hesitant about planting things that have become commonplace after two punishing winters. We've been reminded what can survive and what can't. Camellias and Rhododendrons are very frost-hardy unless you go for more delicate ones.
"There have been big losses but the good news is that our spring flower show (held at Boconnoc on 10-11 April) brought good sales for nurseries because gardeners who have lost plants are restocking on a wide scale."