It has been so mild that bulbs are already appearing as are some unusual plants.
Royal Botanic Gardens, Kew director Professor Steve Hopper said Kew's 50 years of data on 100 flowering species showed a two-and-a-half-week forwarding of flowering since the 1950s.
He added that climate change is galvanising the gardens to instigate a Breathing Planet programme for Kew and its international partners to implement a way forward for repairing and restoring carbon sinks.
Abbotsbury Subtropical Gardens curator Steve Griffith said: "It may be doom and gloom with this wet weather right now, but some plants are shining at Abbotsbury. This is a rare eastern Australian 'Heath leaved Banksia' (Banksia ericifolia). It probably is the only one flowering outside in UK. It thrives here because of our special microclimate and acid soil."