Professor Julia Slingo spoke at the RHS’s second John MacLeod Annual Lecture last Thursday in London.
She explained how a trend towards milder weather is exposing plants to greater risks and that a higher incidence of heavy rainfall also poses a threat.
"Gardening in the UK has always been challenging because of our volatile climate and we have learned to work with it. That has always been the case and it will remain that way in the future," she said.
"However, we have already seen changes in our climate and we can expect more change in the future - so it's fair to say gardening in the UK is getting that bit harder."
She said that the growing season has extended by a month or more in parts of the UK - largely due to milder temperatures in February and March. This exposes plants to a higher risk from frosts during the cold spells we still expect in late winter and early spring.
A trend towards milder temperatures also means there are fewer frost days to kill off pests and diseases in the colder months, helping these plant-threats to thrive.
While there is no sign of any marked change in annual rainfall in the UK, there have been a higher number of days with extreme or heavy rainfall - mirroring a global trend.
She added: "Even with climate change, we will continue to experience the typically changeable conditions that the British Isles are so famous for. This means we'll continue to see a lot of variability in our climate.
"We expect the UK to be buffered from the worst of the warming in future due to changes in ocean circulation, but we will see some changes. Having said that, many of our domestic species are very resilient and I certainly wouldn't rush out to plant cacti everywhere, as they probably won't make it!"