Potted summary: It's time to take cuttings of your favourite plants

But be warned - potting on is a delicate, time-sensitive business, says Anna Pavord

There have been some good things about this summer. Yes. Really. One of them is that I haven't once had to stagger up the bank with a watering can to water the big pots of pelargoniums. It's a steep bank and the can, a French one, takes more than the standard two-gallon English kind. That's a useful trait once you've arrived at your destination, but difficult to manage while you're climbing the kind of slopes on which we garden.

We never had a hosepipe ban in our part of the country. But even if we had, I'd still have been stuck with the can. We have our own water supply. Lovely water, but it isn't delivered with anything like the pressure you get from a mains supply. If you try climbing the bank with a hosepipe in your hand, the water peters out before you've gone 10 paces.

The growth of plants in pots has been astonishing. That's another good thing. It's shown me that, even though in past summers, I think I've been looking after these plants, their potential, given unlimited supplies of water, is far greater. The pale yellow argyranthemums in pots either side of the front door are five feet high and wide. Well, one of them is. The other is slightly smaller – a graphic demonstration of the fact that the size of the pot has an unwavering effect on the size of the plant in it.

The argyranthemums (it's 'Jamaica Primrose') are descendants of a plant I bought at least five years ago. Since then, we've kept them going by taking cuttings. It's easy to do and now's the time to do it. Argyranthemums are not hardy and it's easier to overwinter a few potfulsf of cuttings than to find room under cover for the mother plant, even if it's cut back.

The later you take the cuttings the better. Once rooted, they grow away fast and the problem then is forcing them to mark time before they can be set outside next year. Being tender, they can't go out until some time in May. So, the later you start the process, the less time the rooted cuttings have to spend reined in, under cover. In our quixotic climate, the problem is in knowing how late is later? Leave it too long and your tender argyranthemums will have turned to mush in an overnight frost.

Your cuttings should come from the strong, young side shoots you find sprouting all along the old, thick branches of your plant. In 'Jamaica Primrose' the shoots will be bright green and ferny, though other varieties have needle-like foliage, grey rather than green. Often these shoots break from the angle where a leaf joins a stem. But they are unmistakeable and easy to find.

Not so easy, is to discover a shoot that hasn't already got a tiny flower bud at its head. Ideally, you want non-flowering shoots, but on an argyranthemum there never are any. So choose robust, leafy shots about 10cm/4in long, cut them off cleanly with secateurs and nip out the flower bud straight away. If you are not able to deal with the cuttings immediately, put them in a polythene bag, so they stay as rigid as possible. Don't leave them hanging about too long.

Trim each stem to just below a leaf, then strip off the leaves on the bottom half of each cutting. Fill a 12cm/5in pot with compost – I'm not fussy about what kind I use, though some people swear by coco fibre – and push the cuttings in round the edge of the pot. Firm the compost around the stems with the tips of your fingers. Argyranthemums root very easily, so you don't need to use hormone rooting powder.

Water the pots, but don't cover them, and find somewhere frost-free to line them out during winter. Before I had the greenhouse, I overwintered cuttings successfully in the cold frame. They certainly don't need a lot of heat, but they do need light. A bedroom windowsill may do, provided there's no central heating.

Next spring, you'll soon see when the cuttings have rooted. The stems get taller and sprout new leaves. At this stage, before the roots of each cutting tangle too much with their neighbours, tip out the whole pot and gently tease the roots apart. Set each cutting in fresh compost in its own 9cm/3.5in pot. Press down the compost firmly enough for the roots to make good contact with it, but not so firmly that you squeeze all hope of survival from them. Stand the pots in a tray of water until the compost darkens, then stand them in full light. In poor light, cuttings can become leggy.

The waiting game now starts, during which the argyranthemums will be developing very fast. At first you can contain them by pinching out the growing shoots. But there comes a time when the roots are hanging out of the bottom of the pots you first used. At that stage you need to transfer the cuttings into bigger pots. Sometimes I do this twice, before the plants can go out. Each year is different. Sometimes you risk setting them out at the beginning of May. Other seasons, it may be towards the end of the month.

The potting on is a worthwhile exercise, because it means that by the time you do set your plants outside, they are big, strong well-branched specimens. But they are also brittle and the gales this summer have been legendary. The plants by the front door, always the biggest because they are in the biggest pots, are supported by bamboo canes in a structure almost as complex as the Olympic Orbit tower. Fortunately, the growth is so exuberant, you can't see the underpinning.

Because they have the potential to get so big, you only need one plant in a pot. I generally put the argyranthemum in the middle and stuff trailing lobelia in deep blue round the edges. The lobelia climbs up inside the argyranthemum as well as spilling out over the sides of the pot. The display is as luxuriant now, as it ever was earlier in summer. And all for nothing (well – except for the lobelias).

All our pots now are filled with plants grown from our own cuttings: geraniums of various kinds, two sorts of osteospermums, one pale pink and the other a deep, incredible magenta. You take cuttings of all these in just the same way (and at the same time) as the argyranthemums. Take plenty. Potted up in a decent terracotta pot, they make good presents.