When and how to prune lavender

Saga Exceptional spoke to Guy Barter, chief horticulturist at the RHS, to ask why lavender needs pruning. “Left to its own devices, lavender gets scraggly after just a few years, with woody stems that produce less and less leaf and flower,” says Barter. “Pruning delays this and keeps the bush looking attractive for many years.” 

Pruning can certainly extend the life span of a plant, according to the Thompson & Morgan website: “When properly pruned, some varieties of lavender can last up to 20 years. Left untouched, it soon becomes shapeless and woody, with few flowers and long, bare stems.  

“If you don’t prune, you’ll get a much wilder looking plant – it will become unruly, with gaps and patches inside,” says John Myers, head gardener at the  National Trust’s Ham House and Garden in Richmond. “If you’re looking for a more formal shape or to keep the plant within certain boundaries,” he adds, “it’s best to prune.” 

Apart from keeping your lavender in shape, Myers says that pruning will also help to encourage good flowering next year – a must for those gardeners who like to harvest and dry the lavender buds.  

While some gardeners suggest pruning in mid-spring before growth begins, Barter says: “Pruning after the flowers have finished in late summer works well for us at RHS Garden Wisely.” 

Myers agrees, telling us: “We start to prune around August once the flowers have finished.”  

Pruning at this time has a double advantage if the flowers are past their best, but not brown. “You can cut and save your flowers for pot pourri or for putting into bunches whilst pruning at the same time,” says Myers. 

Tender lavender can be treated slightly differently and will need deadheading over the summer but will only need pruning if it is out of shape. 

I find pruning lavender to be therapeutic – the fragrance is instantly relaxing, inducing a sense of calm to a gardening chore. And although pruning lavender isn’t tricky, it’s worth gaining a few tips from the experts.

Barter suggests using a sharp pair of secateurs or snips, although he does say that “some busy, but steady-handed and bold gardeners use shears or even hedge trimmers.” We’d recommend our best buy secateurs for the job, by Draper.

Your cutting tool will also depend on the size of your plant. If your lavender is small, you’ll want to opt for some garden snips or secateurs, but if you’ve grown your lavender into a hedge, you’ll need something larger, like shears. 

To guarantee a good clean, healthy cut on the plants, it’s worth sterilising your cutting tool of choice before use. Simply clean them with rubbing alcohol or bleach, before rinsing off and drying.

Although our experts have advised that August is a good time to prune lavender, you can look out for the visible signs. Wait until the flowers are past their best, but they don’t need to be brown. 

Before you start to prune, Myers suggests thinking about what you want to achieve: “Are you trying to keep the plant small, or do you want to create a certain shape?”  

“Start by cutting off the old flower stalks,” says Myers, “and as long as you’re cutting into the soft wood, it’s quite easy to cut.”  

You can then start to give the plant a nice shape by removing the leggy branches. This will help the plant appear fuller and will leave it in a good place to develop a new flush of flowers next year.  

Although most of us won’t have the extensive area of lavender that Myers takes care of at Ham House and Garden, we can still learn a trick or two from how he shapes his plants.   

To create a neat, mounded shape, Myers uses a template made of two lengths of wire cut to an equal length. The wire is shaped into two arches and joined to make four quarters at 90°.  

“We place the template into the plant and then cut it in quarter sections,” he explains, “meaning we end up with a lovely mound of lavender.” 

Before grabbing your secateurs, snips or shears, you’ll need to check which variety of lavender is growing in your garden. English lavender, including Lavandula angustifolia and Lavandula x intermedia, is the hardiest variety and needs to be pruned the most. Whereas, French lavender, including Lavandula stoechas, is half-hardy and requires a softer touch.

Finally, tender lavenders, such as Lavandula pinnata – which are not frost-hardy and are best planted in pots and brought into a greenhouse or a conservatory to survive the winter – are more likely to need deadheading rather than a hard prune.  

French lavender can be identified by its small tufty purple flowers, which are like butterflies. It is less hardy and will need replacing after around five years. 

Garden expert Sarah Raven suggests that the half-hardy, French lavender, Lavandula stoechas ‘Sancho Panza’, works well in a variety of different gardens. “It’s an excellent seed-grown lavender, it’s super-early to flower and lasts from May right through summer.” She adds: “Trim it back after flowering or in the following spring to maintain a compact habitat, which will prevent it from becoming overgrown.”