"Nothing is so beautiful as spring. When weeds, in wheels, shoot long and lovely and lush."
The weeds may still be as long and lovely and lush as when Gerard Manley Hopkins wrote those lines in 1877, but they're shooting up earlier than ever according to research on the changing pattern of the seasons.
And that's where you come in. By logging on to our Signs of Spring map you can help us build a comprehensive database of the shifting pattern of this year's unfolding season. Over 1,000 of you have done just that so far.
An equinox happens each year at two specific moments - and 20 March marks the day of the vernal, or spring, equinox in 2009.
From today onwards, days become longer than nights. What happens on the 20 March is that the tilt of the Earth's axis is inclined neither away from nor towards the Sun.
So spring is here - and looking at some of the comments on our map, Today listeners are enjoying the change in season.
"At The Alnwick Garden in Northumberland, the camellia is in flower, first daffodils in bloom, cornus mass in full flower, shrub roses leafing up, and crocus in full flower," says Hilary Ponton. "The doves are sitting on eggs, the first of the chicks fledged four weeks ago."
"Even ants are out earlier than usual...is this all a good thing I ask? Or is it just a natural cycle of our planet that we are not used to?" asks Billy Brown, in St Albans.
And Paul Goldberg from West Kirby found an unusual sign that spring was beginning: "I started my car after work, and the air conditioning unit turned on automatically for the first time of the year."
TUESDAY 17 MARCH
The Today listeners' favourite signs of spring appear to be snowdrops, crocuses, daffodils, bumble bees, butterflies and nesting birds - but, perhaps most of all, frog spawn has a special place in people's minds. Harking back to jam jars and nature lessons perhaps?
We are still in a relatively warm spell. When compared to the 30 year average of 1961-1990, 86 of the past 98 months (since January 2001) have been warmer than average. Whilst December and January were slightly colder than this average period, February was slightly warmer - that will come as a surprise to people who thought February was arctic. It just shows how quickly we change our perceptions of what a typical winter is.
Temperature-wise, Winter/Spring 2009 so far may be close, slightly warmer than the equivalent in 2001. Thus, I would expect spring events to be later than recent years and perhaps 10-13 days later on average across the UK than 2008.
For some of us, 1 March is a critical date for daffodils, and I expect that half the country were disappointed this year.
It is necessary to take a long term perspective. It will probably still be an early spring, but not outstandingly so. Nature's calendar already has 673 records of frogspawn and more than 100 of the brimstone butterfly.
Dr Tim Sparks is an expert in phenology (the study of the seasons) at the Natural Environment Research Council's Centre for Ecology and Hydrology
She has had reports of sand martins in Bedfordshire, the third earliest ever sighting of the bird in the region, and there has even been a report of magpie nest with chicks that have just hatched. The peak time for young birds to be spotted is between April and June.
Ray from Hartlepool has seen a pair of wood pigeons that have returned to their nest for the third or fourth year and says "they look like an old married couple discussing the future". He wonders if they mate for life.
Crocuses along the College Backs in Cambridge, taken on 10 February 2008
The RSPB says that lots of birds - including wood pigeons - do mate over a number of years. While they may spend time apart during the winter, when the breeding season begins they do often return to the same mate.
She also says that the amount of birds spotted will be influenced by the weather. If the weather is mild then more people will be out and about to see birds migrating and breeding. If the weather is poor, then they might just sneak in unnoticed.
MONDAY 2 MARCH
A week into the Today programme's Signs of Spring survey and the response has been fantastic. More than 800 of you have logged reports detailing sightings of everything from crocuses and snowdrops to butterflies and bumblebees.
The overwhelming scale of the response adds to the statistical validity of the findings, and a clear pattern is beginning to emerge.
After a delayed start (thanks to the cold snap early in February) spring is mounting a determined rear-guard action, powering back as milder weather spreads across the country.
The interesting thing from a scientific point of view will be to see how the average dates for a range of events - like the arrival of frogspawn and the flowering of certain plants - tallies with previous years.
Researchers at the Woodland Trust hope to use the information to study the impact of climate change on ancient woodlands.
These complex ecosystems are home to a great number of rare and threatened species, which may struggle to adapt if climate change alters the timing of the seasons.
Tom Feilden, science correspondent
THURSDAY 26 FEBRUARY
Observant spring watchers will have noticed the lone red flag hovering over the Netherlands. It seems spring has sprung in Enumatil too.
But if you think that's impressive try hitting the scroll-out key on the right hand side of the map....
Caroline Solumsmoen may not be able to see the daffs she planted at Skarnes in Norway just yet (the snow's still knee-deep), but the temperature has shot up from -27 to +2 degrees Celcius.
And if you want an idea of the global reach of this Signs of Spring survey, keep scrolling out until you get to the world view.
Pat Whitby-Strevens is reporting miles of Mimosa, fruit trees in blossom and even butterflies along California's highways, while at the other geographical extreme Nori Hayashida needs to get her watering can out in Wakayama.
As for Mr Moore in Edmonton, Canada - sorry Roger, you're just going to have to be patient. Maybe get back to us in April or May.
And while we're on the 'global view' another thought occurs. Almost all the entries are clustered in a fairly narrow band of latitude stretching from northern Spain to southern Norway.
Perhaps that's not so surprising since we're surveying spring in the northern hemisphere, but the correlation with Jared Diamond's view of the rise and triumph of Eurasia is quite striking. For anyone who wants to know more take a look at his book Guns, Germs and Steel.
Tom Feilden, science correspondent
WEDNESDAY 25 FEBRUARY
The response so far has been overwhelming: the snowdrops are out from Helston to Inverurie; Rowena Quantrill
spotted a Brimstone butterfly near Bradford on Avon earlier in the month; Tim Stapleton
has bats flying and hedgehogs foraging in his Wakefield garden; and there seems to be enough frogspawn around to reverse the ongoing decline of amphibians at a stroke.
According to the Met Office, this winter was actually the coldest since 1996/7.
Eleven years may not be much of a record, but it does seem to have bucked the trend - delaying spring by a few days and getting it back to something like the long term average.
The biggest study so far, published in the journal Global Change Biology in 2006, found that the arrival of spring had shifted significantly over the last 30 years. Average flowering and fruit ripening dates had advanced by six to eight days across Europe, while autumn was occurring up to three days later.
The question now is whether the cold winter has simply set spring back to its longer term average, or whether we're in for a riotous explosion of colour, frogspawn, and gambolling lambs as nature hurries to catch up with the new timescale.
We need your help to do that, so please, keep the observations coming.
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