Quick, quick, grow Posted on July 7, 2008

Yesterday we were praying for rain. Three weeks of dry, if not hot, weather had stopped the garden growing. In frustration we resorted to the only effective rain-dance: inviting friends to lunch in the garden. That worked, with unusual precision; a squall at one o’clock. It only measured 2.5 millimetres, a tenth of an inch, in the rain-gauge, but by tea time the new growth was measurable on almost every plant.

How do plants produce new shoots instantaneously? It is most remarkable, I always think, on oak trees. Pale, usually reddish or pinkish, ‘lammas’-shoots break out all over the dark green crown. I measured one three hours after yesterday’s shower; eight inches of pale shoot with 15 new leaves had appeared from nowhere – or rather from inside a tiny bud at the end of a twig. Was it already formed, packed in there in micro-miniature? How do cells spring into instant action, forming all the diversity of twig, leaf-stalk, leaf, and indeed new buds containing all these things again, within minutes of water being available. What principle, and what urge, starts, plans and determines growth?

I can only imagine that roots in the ground when soil moisture is in short supply are like runners on the starting-block, primed to sprint. Rain dampens the surface, even as little as a few millimetres, and the signal goes out: get growing. The pent up sucking-power of billions of tiny root hairs, all intertwined in the soil, hoovers up the molecules of water, they shoot at incredible speed up the cambium corridor of every plant and cells start their programmed growth. How do they know how much to grow, or how many molecules their allowance will be? They are miraculously able to seize the opportunity, start and stop again as supplies are turned on and off. I went slowly round the garden last evening, smelling the dampness and the growth, finding evidence of movement in almost every plant I looked at.

Pines are an example of a plant that has no active buds until next spring, and no way of making adventitious ones – which is why rain doesn’t make them grow, and when you cut one down it can’t recover: a felled pine is a dead pine. Not a yew, though, or almost any other plant. The yew hedges are covered in spots of pale new growth. The border flowers are surging; the roses and every other shrub breaking out in tender growth. But strangest and most wonderful of all is that only rain can make this happen. You can water your plants as much as you like; they still only react like this to a shower.

So lots of garden parties.

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