Thumbnail Posted on June 13, 2010

I’m not sure what it would be called if you did it to a sentient being, but I’m certain it would be against the law. In so far as a plant has instincts and urges they are controlled and expressed by its hormones. Can it be legitimate to frustrate them?

At this time of year, when plants are in active growth, their messages are plain to see: the priorities of one bud growing before another, the rationing of vigour between one shoot and another; the election, as it were, of a leader (or the equal energy of several branches) are all determined by hormones.

And we, superior beings, seeing how they are programmed, can outwit and re-direct them as we please with our forefingers and thumbs.

If you wait until the plant has obeyed its hormonal instincts and grows its branch or its truss of flowers you call it pruning (a verb, oddly enough, with no apparent roots or relations). You then have the wasted effort, the amputated stems and leaves, on your hands, your compost heap or your bonfire. Better, surely, to take the initiative and preempt unwanted developments.

A florist disbuds to get bigger and better flowers, choosing to concentrate the available energy into one flower rather than two. I bully my young trees and shrubs in the same spirit, examining them to see what buds have opened, with what consequences, and what buds are next in line. If a new shoot has set off in a direction I don’t approve, I look for another with ideas that more nearly match my own and eliminate the first. At this early stage my thumbnail is usually the ideal tool.

There are plants with such simple and deliberate ways of branching that errors are obvious. Fir trees put up one leader surrounded by incipient branches like a ring of spokes. So strong is the hormonal drive to keep going north, as it were, that when a pigeon lands on and snaps a newly-grown and still green leader (its wood unripened and fragile) one of the spokes gets a hormonal command to take its place. How does this work? The growing cells on the underside of the chosen shoot (chosen by whatever mysterious form of election) begin to multiply further than the rest. The shoot bends upwards as result. Very soon its terminal bud becomes the highest point of the tree, the leader and hormonal dictator. It even develops buds all round in readiness for a new ring of spokes next year.

Intervention is pointless with such a clearly-programmed plant. When a rather splendid fir in the garden here lost its leader to a bird in the usual way I did try to help it, from a ladder, tying a light bamboo to the top of the trunk and hoisting one of the side branches into the leadership position, secured with string. When I came back two months later the tree had ignored my advice and produced a new leader from a spare top bud lurking among the needles.

There are deciduous trees that seem to share the fir’s philosophy. Alders often have the same simple spoke-like rings of branches; many poplars, too. You can count the age of trees of this persuasion: it is the number of rings of branches – up to the point where circumstances take over: breakage or uneven light and shade modify the simple pattern.

It is oaks that keep my thumbs busiest. Quercus is quirky. An English oak rarely leads with an end bud pointing straight ahead. It has buds in clusters that seem to leave all its options open, to grow into whatever space offers most sunlight. In a crowd of seedlings this will usually be straight up, but an oaklet with equal illumination all round will hesitate, first prefer one direction and then another, and soon become a tangle of zig-zag branches with buds pointing in all directions.

Welsh sessile oaks are worst; herding cats is straightforward compared with directing a vigorous little Welsh oak tree. It may seem obvious which branch or shoot is dominant and should be encouraged. There are never less than four buds on each shoot, though, ready to surprise you. I suppress three with my thumbnail, or snip little shoots with my secateurs, favouring the one nearest to vertical. I’ll come back weeks later, to find all the tree’s energy has gone into a bud I didn’t notice, heading for Machynlleth.

It’s a curious hobby for a grown man, I’ll grant you.

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