Plant of the month - January

Pyracantha 'Saphyr Jaune'

These little jewels have been cheering up my garden since last autumn. Pyracantha can be the only really bright colour shining through the dull months of winter, and they're all the more welcome for that. The birds have snaffled the red and orange berries already - I have P. 'Saphyr Orange' and P. 'Saphyr Rouge' planted along the same fence, and they're meant to mix 'n' mingle, but the yellow is all that's left. No complaints here, though - I'm just grateful to have such a dainty little sprinkling of colour at this time of year.

Pyracantha is one of those shrubs which is doing something useful all year round. I keep mine trained against the fence - I find they become badly-behaved thugs in the border if left unsupervised. If you're strict with them, though, they behave themselves beautifully. They're one of the few plants which provides evergreen climbing cover all year, and as a sideline are excellent security - climb over a fence clad in pyracantha and you won't forget it in a hurry. As if that wasn't enough, they froth up with flowers in early summer and then sparkle all winter too. I wouldn't be without them.

Hacking at lilacs

This is a great time of year for cutting back overgrown shrubs, especially spring-flowering ones. Lilac is a prime target, as well as evergreen ceanothus, berberis, pyracantha... pretty much anything that doesn't flower later this year, really.

I spent a couple of hours laying into a client's lilac last week. It must have been 20 years old, and about that long since it was last looked at: it was heavily congested in the centre and the 4" thick branches were splaying outward and endangering his shed. And it was about 25-30ft tall, which would have been fine in a big garden but his is a small-ish suburban strip.

I like to think of this kind of pruning as rejuvenating pruning - though it also counts as common-or-garden hacking back. What you do is remove about a third to a half of the wood - taking out the thickest, oldest branches first, and then any which are pointing in the wrong direction, as well as any which are diseased and/or dead, of course. If you're me, you find it hard to know when to stop, especially with lilacs: when they're overgrown, they tend to develop long, leggy stems with the leaves and flowers right at the very end, and that means once you've taken out the bulk of the shrub, you're left with some rather sad-looking whippy lengths of wood waving around in the breeze. It all looks very odd.

Fear not: this is quite normal. The thing to do is to leave it looking a bit wierd this year, and wait until the stump starts pushing up new growth, which it will do very quickly. Then next year you can cut out another third of the long whippy old wood; and by the third year, when the new growth has got to a decent height and will be flowering well, you can take out the last third to be left with a bush that's all the same height, hopefully a nice shape and full of strapping young growth which looks far nicer and is much more healthy.

Back to the wall

I've been giving my ceanothus a haircut this week, as it's trained against a fence and needs an annual prune to keep it tidy.

Wall-training shrubs which are otherwise inclined to get a bit big and unwieldy is a great way to keep them in bounds. Ceanothus is a good candidate, and so is Japanese quince (Chaenomeles japonica), pyracantha and Garrya elliptica. The small-leaved cotoneaster, C. horizontalis, holds itself so rigid it practically stands up against a wall by itself, without supports.

The principle is pretty straightforward: you'll need supports, such as wires spaced about a foot to 18" apart, to train the shrub onto before you start.

Then, year by year, you shape the shrub so it's flat against the wall. You do this just after flowering: just prune out any branches growing out away from the wall completely or, if you're at risk of ending up with bare stems, you can prune back to one or two leaf joints from the stem.

Tie in side shoots pointing the way you want them to go, and then trim any upward-growing stems to about an inch (2.5cm) below the top of the fence or wall. If any longer side shoots are growing beyond the bounds you want them to keep to, shorten them, too.

Pyracantha in particular makes a really lovely espalier if you do this: ceanothus is a bit more bushy, so you get a pleasing evergreen "coat" to disguise your fence with. In any case, you avoid the problem you get with climbers where they're forever climbing next door, or over the neighbouring shrubs; and it looks great, too.