It ain't necessarily so: if spring flowers are appearing remarkably early in your garden, it's not always because of climate change (although it may be).
Several recent letters to The Independent have highlighted examples of plants flowering early, and many have suggested a perfectly valid reason: it's what some varieties do naturally.
Daffodils are a perfect example. The daffodil is usually thought of as the archetypal spring bloom, and the poet A E Housman (author of A Shropshire Lad) called it "The Lenten lily, which dies on Easter day." But several cultivated varieties of daffodil flower naturally before Christmas, while some wild species can flower as early as October.
Two of the best known are Paper White, and Rijnveld's Early Sensation (often known as just Early Sensation). Both are out now.
Paper White is a wild species from Greece and the eastern Mediterranean islands such as Crete ( Narcissus papyraceus) and a good place to see it is the rock garden at the Royal Botanic Gardens in Kew.
"We've got about a dozen clumps of it," said Richard Wilson, Kew's Collections Manager for Alpines and Bulbs. "We don't plant it out as an amenity – it's in a naturalistic setting, although they are perfectly suited to any garden." He added that the bloom this year was early, but made the point that it had been known to come out in early November.
Early Sensation is a cultivar – a cultivated variety – rather than a species in its own right, and it too is now in full flower, according to Leigh Hunt, horticultural adviser for the Royal Horticultural Society.
"It's a very early variety, and it's been opening its buds since before Christmas," Mr Hunt said.
However, even gardening experts were surprised when Early Sensation joined Paper White in massive displays of blooms in early November at the Eden Project, in Cornwall.
Although some daffodils and narcissi can naturally flower even earlier – a species called Narcissus serotinus from Morocco can come out in October, Mr Wilson said – it remains the case that many well-known varieties are flowering much earlier than 15 years ago, in a way that seems consistent with a warming climate.
Kew's most spectacular daffodil display is a case in point – the dense swathes of rich yellow flowers which line the Broadwalk, the road linking the Orangery to the Victoria gate.
These are the February Gold variety, which in the past, Mr Wilson said, seemed a misnomer, because the flowers typically appeared in March. But now they were misnamed the other way, he added, as they were tending to come out in January.
"Ten to 15 years ago we were lucky to get it flowering in February – it was usually March," Mr Wilson said. "These days it flowers in January so you can really see the difference. It's flowered in January quite consistently for the past few years."
February Gold is just coming up at the moment along Kew's Broadwalk. So is another daffodil – the English wild daffodil, Narcissus pseudo-narcissus .