Liquid assets: If a garden is properly looked after, there's less need for watering than you might imagine

Dictionaries are wonderful time-wasters. I've just looked up "sustainable" in mine and been waylaid by Sussex spaniel ("a short-legged breed of spaniel with a golden-brown coat"), sutra ("Sanskrit sayings on Vedic doctrine") and sutler ("a merchant who accompanied an army in order to sell provisions to the soldiers").

But of all eight definitions given in my dictionary for the word I was actually after, none fits the way that "sustainable" is now used (over-used) in relation to gardening. What I think it means is gardening in a way that respects the needs of the soil, the creatures that depend on it and the things that grow in it and that does no harm to our neighbours or ourselves. When we leave our plots after however many years, we should feel they are in good heart, at least as good, if not better than when we took them on. It all sounds very worthy.

And it is. The pity is that it needs spelling out. Gardening by its very nature should be a sustainable activity. The get-rich-quick boom didn't help at all, but when the concrete-paved patios start to crumble and the gas barbecues begin to rust, there is a chance that at least some of these too-quickly-made-over gardens will be able to settle back on their haunches and find a more natural equilibrium.

Taken to its limit, sustainable gardening would not include any activity that, if we removed ourselves from the scene, could not continue without us. That would mean no plants in pots, no heated greenhouses, no lawns. It's not going to happen, because the crux of gardening is intervention. We tweak things to make them perform in ways that benefit us. We can, though, look carefully at the way we do things so that when we are hauled up before the Sustainability Board, we can put up a robust defence and not appear too selfishly self-centred.

"Pavord. Account for your water consumption." "Pavord, why the bought-in compost?" "Plants from abroad, Pavord? Why not British natives?" Let's start with water. After yet another summer when it barely stopped raining, it's hard to hang on to the concept that water is a scarce resource. But we get droughts too, and gardens have to survive whatever weather is thrown at them.

If a plant is carefully planted, at the proper time of year (usually autumn rather than spring), watered well and mulched, it generally should not need watering again (I'm talking of plants put in the ground, not in pots). But gardeners like watering. They feel they are doing good and it is a restful, soothing activity. The water makes a pleasing sound as it hits foliage and the damp earth gives off a special musty smell.

If there are not too many hard surfaces in a garden, if rain has a chance to soak into most of what it meets on the ground, if the ground is mulched every year with a thick layer of mushroom compost, composted council waste or whatever takes your fancy, regular watering should not be necessary. As always, there are lots of ifs: we get plenty of rain; too much tarmac, too much concrete. But laid on over soil that is already damp, a mulch prevents water evaporating from the surface. And as it is gradually pulled down into the earth by worms (which will be glad of the humus), the mulch acts as blotting paper, giving substance to light soils and a means by which it can hold dampness in itself.

Even if you do need to water, you don't have to use expensively treated stuff from the mains. Water butts are an extremely effective way of storing rainwater. We have three – two big wooden barrels and one galvanised trough. They just sit on the ground and I dip cans in the top. Often a canful of water is all you need, to slosh over a tomato plant or petunias in a pot. The butts are dotted about in various places, picking up water from different roofs, so I never have to stagger too far with cans.

I can't remember when we last got out a hose. Here, anyway, they are of limited use. We don't have mains water; the supply is pumped from our bore hole up to an underground reservoir at the top of the garden. If you pull a hose pipe to water anything up the bank, the pressure soon gives up. I imagine the Sustainability Board might listen to an argument for hosepipes though. Automatic irrigation systems would have a rougher time. And I'd agree. They are wasteful, unsightly and turn a garden into a hospital, the plants hooked up to their tubes like patients in intensive care. And they are death to many bulbs, which in order to flower well, need a summer as hot and dry as they can get. While the summer delphiniums may be coping with your automatic system, the spring tulips waiting underground will be screaming for help.

A more insidious difficulty for gardeners wanting to garden sustainably is the obsession with recycling. This sounds contradictory. Recycling is good, isn't it? No, not always. Achieving recycling targets gets in the way of what we should really be doing, which is using less of everything. But we are urged to consume, because it's good for jobs. That lorries travel millions of miles carrying materials of little worth to faraway dumps does not form part of the equation.

I went to a garden centre recently to buy a large black plastic pot – a rare purchase, since I never throw away a plastic pot. They hadn't got the size I needed but the kind woman on the till said she'd seen some in the shed set aside for recycling plastic. Perhaps I could have one of those. "Great," I said. "I'll put the price of the pot in your charity box. We'll all be happy." All except the man who had taken charge of the shed. "Once that plastic is inside that shed, it stays there until the recycling lorry comes to collect it," he said. "We've got targets to meet."

"But aren't I your perfect recycling opportunity?" I pleaded. "I can re-use the pot just a few miles away. It'll leave more room in your shed for stuff that can't so easily be used again. And your charity will get some money it might not otherwise have had." But he was adamant. The shed remained locked.