It’s time to prune those woody herbs

Lavender, thyme, rosemary, sage: they all need a trim every now and again

There is a lavender at the bottom of my street that has grown so wild it sprawls through the fence; you can see a line along the flowers where passersby can’t help but caress its fragrant blooms. I’m one of them. I like its dishevelled nature, but I’m not sure it would work in a garden. Its bare legs and gaping belly would make it unsightly.

Woody herbs such as lavender, thyme, rosemary and sage, as well as the less-woody-but-still-woody-enough oregano and winter savory (Satureja montana) do need pruning. Left to their own devices, they become leggy, with the woody parts bearing few or no fresh shoots.

In the Mediterranean heat, these herbs are clipped by nature – thin soils, baking summers and strong winds will keep them neat enough. In our wetter, milder climate they grow in a different manner, so it’s important to prune them regularly – once or perhaps even twice a year – to keep them in a nice shape.

The best time to prune is early spring, but there is a second chance now, once flowering is over. Remove the spent flowers and cut the stems back to a pair of leaves on no more than a third of the overall plant. Next spring, cut another third and you’ll find your herbs will stay in a good productive shape.

It is almost impossible to get back to a neat, bushy plant once it’s grown big. This is because the woody parts tend not to resprout new growth; if you chop back into this, you will be left with stubs and little else. In this case, it is better to take cuttings or start again than to try to renovate the shrub.

Cuttings are easy enough, though. Choose non-flowering growth and cut sections of stem that are 10-15cm long. Remove the lower pair or pairs of leaves so you have a clean stem, then, with a sharp knife, cut just below a pair of leaf nodes (the point from which the leaves grow). Then place cuttings in gritty seed compost (mix equal parts grit and compost) and water well. Place them in a warm, shaded spot and keep well watered. Or, if you are taking the cuttings indoors, place a clear plastic bag over them to retain moisture.

In a few weeks you should start to see roots at the bottom of the pot. If not, carefully invert the pot and check what’s happening in the soil. The RHS website has a good page on herb cuttings if you are nervous.

If your lavender suddenly turns into an awkward leggy teenager, then it is possible to cheat and do the “dropping” trick if it is not too big. Dig up the plant, dig a deeper hole and replant so that only the leafy growth is showing; essentially you bury the woody stems. (Do not try this on a hot day or if the plant is in flower.) The soil must be gritty, otherwise the stems will rot. Keep the plant well watered till you see signs of new growth.