The pale blue, purple, pink or even white flower spikes of lavender have brightened gardens throughout the summer, but with autumn fast approaching the plants are now due a haircut. Removing dead flower spikes annually should keep lavender thick and bushy and prevent it from forming unsightly woody stems, but don’t be tempted to prune more drastically.

If you haven’t kept on top of your lavender and it’s become hopelessly woody, you may need to howk it out and plant a new one. Before doing this, however, try renovating the plant with heavyweight pruning next spring. If the plant’s healthy and not too old, it might just work.

When your lavender starts into growth next year, start pruning by gently brushing the branches to knock off any dead foliage. Then cut back half the old grey stems to a few centimetres above the ground and remove any obviously dead stems. If you see green buds sprouting near the base of any uncut stems, cut those stems to immediately above the bud.

This thinning lets more light into the bush, encouraging new buds to grow rather than die off. After this preliminary pruning, keep an eye on the plant and cut back old wood as soon as you see new growth at its base. By early summer, you’ll have cut back all the old woody stuff and, after a few weeks, you can use secateurs to start shaping the bush as you’d like. Eureka! The following spring, you’ll have a bushy wee plant, all ready for its light autumn prune.

There’s no doubt lavenders aren’t the easiest plants to grow. They need every last ray that the weak Scottish sun has to offer. Drainage is equally important. Few plants tolerate standing water, and lavender won’t cope with heavy clay soil, so light, very free-draining soil is vital. Although some lavenders come through very cold winters, when temperatures sink as low as -15C, wet roots will kill them. I have a very free-draining bed where lavender has grown beautifully for quarter of a century.

Yet, despite these problems, folk have grown lavender for millennia. Admittedly, people valued its usefulness rather than its beauty. The Romans had lavender on the lengthy list of plants they introduced to Britain, partly because they valued its cleansing properties for cuts and wounds and improving the water quality in their baths – no bad thing since their personal habits reputedly weren’t the best.

Since Roman times, lavender has been used as an insecticide, repelling fleas, nits, mosquitoes and midges. I was interested to come across a recent Spanish study that found the herb was even a useful deterrent to the potato peach aphid.

Even if we don’t use lavender as an insecticide, we can enjoy its hint of fragrance in sweet and savoury dishes. But, most importantly, who can’t help enjoying the pungent fragrance of lavender on a calm summer’s evening? My long-established lavender grows at nose level in a bed that slopes up from a dyke.

If you’re planting lavender in the open ground, always choose a Lavandula angustifolia variety. Given very free-draining soil, this species should handle most Scottish winters. You could extend your colour scheme by planting the white-flowering Nana Alba.

Be sure to plant other, more tender species in pots to give them winter protection. Growing to only 30cm, Lavandula stoechas Kew Red, from southern Spain, is a perfect candidate for this. Lavenders from Africa and the Canaries certainly need winter cosseting. While enjoying the pale purple flowers of fringed lavender (Lavandula dentata var candicans) your eyes will be drawn to its finely serrated leaves. The silvery, lacy foliage of Lavandula x Christiana, with its stunning blue flowers, is every bit as appealing.