And you thought it was the daffodil. But no, Wordsworth's favourite wild flower was actually something quite different.

And you thought it was the daffodil. But no, Wordsworth's favourite wild flower was actually something quite different.

The bloom that captured the heart of England's greatest nature poet is smaller and comes out earlier as the first flower of spring (the snowdrop appears at winter's end).

It is the lesser celandine, a bright-yellow member of the buttercup family, which brings the first splash of colour in the last two weeks of February. Wordsworth wrote three poems about it, and only one to daffodils - "I wandered lonely as a cloud" - which is better known.

So the grand old man would be pleased to find that 200 years after he wrote about them, lesser celandines appear to be spreading more successfully than any other British wild plant.

Their success is shown in the annual survey of Britain's flora by the wildflower charity Plantlife. The Common Plants Survey, which checks 65 familiar species, tries to do for plants what the long-running annual surveys of the British Trust for Ornithology (BTO) have done for birds. Begun in the 1960s, the latter have shown with startling clarity and statistical robustness the fluctuating fortunes of Britain's breeding birds.

The BTO and Plantlife surveys are done by volunteers who report on species in one area over the years. The Plantlife survey began only in 2000, so the data available is not yet long enough to establish definite trends. But the lesser celandine has appeared in 35 per cent of the monitored plots in 2000-04. Ranunculus ficaria is not very mobile, so this is a puzzle. Five species seem to be going down: bird's-foot trefoil, red clover, great willowherb, meadowsweet and silverweed. Plantlife says it is too early to give reasons. The charity, which can be e-mailed on enquiries@plantlife.org.uk is very keen for more volunteers for the survey.

Wordsworth appreciated them as harbingers of spring. This may be the origin of their name, which appears to come from the Greek word chelidon, meaning swallow. Although celandines appear two months before the swallows, they might be thought of as their flower-equivalents.

The lesser celandine is not to be confused with the greater celandine Chelidonium majus, a much more upright plant from a different family (poppies, rather than buttercups).

This confusion affected Wordsworth, after he died. Such was his love for the smaller flower it was suggested as a decoration on his grave at Grasmere in the Lake District. But the mason mistakenly put the likeness of the larger plant on his monument.