Spring builds like a wave, slowly at first, gathering pace. Shivering snowdrops raise their heads, followed by crocuses and swathes of golden celandine, harnessing the winter sun. Gaudy daffodils, then clouds of blossom, herald the imminent explosion of green as the world unfurls into leaf. ‘Green havoc’, Fiona Benson calls it – add in the birds for a cacophony of sound, and colour. Meanwhile, tumbling over hedgerows, come great drifts of cow parsley, their pure white spume frothing on the crest of this elemental wave.