It could be described as a form of "compulsion neurosis." To which he says "Bosh. I just do it to keep interest in life going, to keep my sense of curiosity well tuned. And if you want any more explanation, I do it just because I damned well enjoy it."
And what he does is merely, each autumn, to pot up a few seeds of trees, chiefly oaks of various kinds, and there are many also pines of obscure nomenclature, maybe ash and some other odds and ends. Say rowans. But always with the idea of growing trees from seed. And isn't that a slow process? No give them the right start, and the trees will soon be towering over you.
And does he plant them all in his own patch of a few acres? No.
See later. He has almost, though not quite, reached the stage where he will be cutting down trees to make way for the pushing seedlings. He can always squeeze a few more in. And, anyway, timber is a self renewing force. Ash is sprouting from the stumps of trees he had to cut for one reason or another. The view perhaps. That's coppicing, and more wood eventually.
He teases out with a good friend with whom he now and then swaps seeds, whether it is, in fact, better to keep, say, acorns in a cool, dark place all winter and then plant them in pots when the weather warms up in a normal spring. Or to pot them directly in autumn. Both declare with dismay that there is not a sign of a single kermes oak of which they have each planted a number of acorns. It's all a bit of a gamble or, to take an angling comparison, somewhat like a slow motion version of casting a fly on the river surface and waiting for the tug in this case a tiny, pink emerging shoot.
So he usually has some small trees to dispose of to friends by the late summer? Yes. Or even some acorns to spare in autumn? Yes. Well, that puts a less self centred interpretation on it. Is it mainly that it keeps him young? you ask. Answer. "It keeps me alive and sane. A sense of wonder is worth any amount of pills and vitamins."