Warm weather is causing a number of plants to flower as much as two months earlier than usual. In 2010, the UK had one of the coldest Decembers on record.
But last year returned to warmer temperatures, which reached as high as 14.5 degsC. As a result, spring plants such as snowdrops, camellias and crocuses are already flowering, while some autumn-flowering plants have remained in bloom.
Ed Ikin, head gardener at the National Trust's West Sussex Nymans Estate, said the cold winters of the past three years led to more defined seasonal displays. "The danger of a milder winter is that there might be a less concerted spring display, with things coming out in dribs and drabs," he said.
Ikin added that some plants were flowering two months early. "At Nymans we haven't really had consecutive frosts," he said. "We've had two, but neither was particularly hard, not going below -3 degsC.
"The most distinctive example has been camellias, which we had flowering in late December. We also have two crocuses flowering and snowdrops are coming out.
"We are about two months ahead. The plants haven't had anything to tell them that it's winter. It's surprising that these natural mechanisms are often quite crude - it's just temperature."
Chris Clennett, garden manager at Wakehurst Place in West Sussex, added: "Plants we expected to finish one or two months ago have carried on and plants that would normally have stopped flowering carried on."