They are worried down in Shelsley Walsh in Worcestershire. I was there the other night to give a talk to the gardening club, and the conversation was all of daffodils flowering before Christmas, primroses flowering in January, and a ceanothus which had been flowering all winter. Lent started early this year (Ash Wednesday was February 9), but the Lenten roses (Helleborus orientalis) were even earlier: mine were in bloom on New Year’s Day. And as for the summer snowflake (Leucojum aestivum), one clump in my garden was in flower almost before the snowdrops were out.
But while many plants, birds and insects are breeding, flowering or coming into leaf earlier, some spring events quixotically seem to be getting later. A gap seems to be opening up between the oak and the ash, with oak coming into leaf ever earlier, and ash lagging behind. Hawthorn and horse chestnut are racing away, but the time when beech comes into leaf seems to be getting later and later — and not just in relative terms. So what’s going on?
It seems that we are in for longer and increasingly chaotic springs. Instead of everything straightforwardly happening earlier in response to the warming of the climate, phenologists like Tim Sparks, of the Centre for Ecology and Hydrology, are beginning to realise that the picture is rather more complicated. (Phenology is the study of periodic biological phenomena such as flowering or migration in relation to climate.) Official phenological records were kept in Britain by a national network of recorders between 1875 and 1948 but then lapsed until Sparks revived the network in 1998. By linking the earlier records with those of the past seven years, Sparks is able to go beyond anecdotal evidence and discern some pattern in all of this.
Most plants have a period of dormancy to protect themselves from adverse weather conditions: tropical plants, for example, become dormant in dry or cool spells, sending up new shoots when the rains return. In our higher latitudes, dormancy is a product of complicated responses to a number of factors, such as day length and the temperature of soil and air, not all of which are understood. Oak responds to higher temperatures in spring by coming into leaf eight days earlier for every degree of warming, whereas ash comes into leaf only four days earlier — as if some other mechanism were halting its response to the rise in temperature. That might be sensitivity to day length, or it might be several factors. According to Dr Phil Gates, of the University of Durham, beech buds contain a hormone which inhibits bud-burst. It needs cold to break it down. So if there is no cold spell, the buds take longer to awake from dormancy.
The naturalist Richard Fitter recorded the date of flowering of more than 500 plant species over nearly 50 years. His data have now been analysed by his son Alastair Fitter, Professor of Biology at the University of York, and he too has discovered anomalies. He told me that insect- pollinated plants have responded to warming more than wind-pollinated ones such as grasses and trees. Annuals have responded more than perennials. And while one in six species is flowering up to two weeks earlier than a decade ago, others (such as buddleia, coltsfoot and whitebeam) are flowering later. In any given habitat this may alter the balance between species, so that some die out as a result of increased competition. New hybrids may also emerge between species which have not previously flowered at the same time, such as water mint and field mint. Red and white campion already do this, and in some parts of the country the hybrid is more common than either of its parents.
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So things are going to be interesting in gardens with plants from all over the world living cheek by jowl. But this may have more serious consequences in the wild, if the links in the food chain start to come apart, and a gap opens up between the time a species starts producing its young and the times when its preferred food source is available. Species which have a single food source are particularly at risk, such as the larvae of some fritillary butterflies which eat only violets. Birds are likely to fare better: earlier breeding may mean that they miss the caterpillars they are used to but, being more omnivorous than butterflies, they should find plenty of different ones with which to feed their chicks.
Contribute your own spring sightings to the UK Phenology Network’s website at www.phenology.org.uk or by logging on to bbc.co.uk/nature/animals/wildbritain/springwatch
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katherine.swift@thetimes.co.uk