Anna Pavord: 'Pelargoniums need a roof over their heads at this time of year'

It's not often I feel virtuous. It is, anyway, an irritating trait. But while washing the glass of the greenhouse windows, I felt surprised that I could be doing the kind of task that your eye usually skims over when viewing your jobs for the week. However, it's been changeover time in the greenhouse with summer stuff hauled out and winter stuff waiting to come in. In winter you need as much light as possible in a greenhouse, so the plants don't get drawn and leggy. Hence the washing: a splash of Flash in some warm water and a drying off rub with crumpled newspaper.

Fortunately, there wasn't too much to do as the greenhouse has two solid walls, and breezeblock up to four feet on the other two sides. That keeps the place well insulated, as well as cutting down on the cleaning. We keep it just frost-free, which is enough to overwinter cuttings and bring on some seedlings of annuals for next summer.

A mild autumn, such as this has been (one of the most beautiful I can remember) means you keep putting off jobs such as taking cuttings of geraniums (pelargoniums), osteospermums and other tender plants. It's a lottery, guessing when the first frost will come, but I like to leave the job as late as possible. Otherwise, you start running out of space in spring, when it's still too early to be able to plant out the things you have raised from cuttings and which will, by then, be bursting out of their pots.

But as October wore on, I felt the odds were shortening, so the cuttings were taken and the greenhouse cleaned up to receive the new guests. By this end of the season, the aforementioned delicate specimens have made masses of growth.

What you look for are shoots (if possible non-flowering ones) that come out from the main branches and which are about 8cm/3in long. Snap these off and take the shoots to wherever you keep your pots and compost. I use pots about 13cm/7in across, filled with multi-purpose compost. Firm it down and poke five holes round the edge of the pit. Trim your cuttings just below a leaf joint, and strip off the biggest leaves. Then poke a cutting in each of the holes you've made, firm down the compost round them and water the pot. I do this by standing the pot in a tray of water, rather than by watering overhead.

That's it. It couldn't be simpler. Some people use electric propagators. I never have and the cuttings root fine. They just take a bit longer. The pots stand on long plastic trays set on a narrow wooden shelf that runs along just under the roof of the greenhouse. They are useful, these shelves, for seedlings as well as for cuttings. Getting them as close as possible to the light source stops them getting “drawn”, with thin unstable stems.

Most of the things that fill the big pots outside in summer, I keep going from year to year with cuttings like this. There are four different pelargoniums, all grown for their scented leaves, rather than their flowers. Most important is “Lady Plymouth” which, being variegated, doesn't strike as readily as the green kinds. It was first introduced early in the 19th century, but it's still a superb pelargonium with creamy, deeply cut foliage that smells of roses and bulks up beautifully in a pot.

The flower is mauveish and insignificant. But you don't grow scented-leaved pelargoniums for their flowers. You grow them for the massy, generous quality they give to pots and for the pleasure of reaching out, whenever you pass, to press a leaf and release the wonderful smell. “Lady Plymouth” will grow about 50cm tall and spreads at least 40cm.

The others I grow are “Candy Dancer” which has crisp, very deeply cut leaves, and peppermint-scented “Chocolate Peppermint” with huge hairy leaves, dull green with a chocolate-coloured blotch in the centre. This is a useful plant because it will grow happily in semi-shade, whereas most pelargoniums prefer sun. It's lax in its habit, spreading to at least 60cm, while only about 30cm tall.

In terms of scented-leaved pelargoniums which also have decent flowers, the best is “Pink Capricorn”, which has plain, soft grey-green foliage, faintly lemon-scented. The flowers are a clear rich pink and if you dead-head (another virtuous job…) will flower all season. I take cuttings of this too, but also, at this time of year, bring in a pot of fully-grown “Pink Capricorn” to sit on a windowsill in the house. There, it will go on growing and flowering all winter. It won't block the light as it never gets much more than 30cm tall. The stems splay out as they grow to make a plant about 50cm wide. Give it a sunny place and keep the compost dryish.