A hardy plant for sunny dry spots and one of the longest-blooming semi-shrubs around, lavender (genus Lavandula) would earn a place in most sunny gardens even if it didn’t have such a heavenly scent. There’s more good news, too: lavender is easy to prune, and when you do it, you’ll be covered for the rest of the day in those aromatic oils. This is one of the few gardening tasks that’s good to do just before a hot date!
Lavender: a Semi-Shrub to Tame
Lavender is a semi-shrub (or subshrub)—a plant that looks like a perennial because most of its growth is soft and green, but its older base stems will turn to wood. Knowing this is going to help you prune your lavender. Deep at the center of the mounded semi-shrub, your lavender plant is trying to turn to wood. One goal of pruning lavender is to slow down that transformation, for a few reasons:
- Lavender wood is very weak and prone to splitting under snow, ice, and water-rot.
- Unlike many true shrubs and trees, lavender wood that has formed usually does not rejuvenate.
- Old wood will stop producing new shoots or will produce spaced-out shoots, destroying overall appearance.
Pruning heavily every year will help slow down the formation of wood and extend the vigor and lifetime of your plant.
General Tips for All Species and Varieties
Start pruning your lavender plants while they are still young. If you begin by pinching tips of new growth when the plant and its growth are very young, it will respond vigorously with dense branching that helps form a good shape and a lot of blooming growth to work with later. Waiting to prune lets the plant form older—eventually woody—growth that responds less well to pruning.
The best time to prune is after flowering, but lavender is forgiving. All lavenders bloom on the stems that grew in the current year. This means that pruning can be done in early- or mid-spring without sacrificing the current year’s flowering. Pruning in spring can delay flowering—which might be your preference—and is a good time to take down dead, winter-killed parts and shorten growth to the fat, vigorous buds. Pruning in late-summer or early-fall encourages good air circulation, which guards against rot. If you have the time, pruning twice a year is ideal.
Prune established plants heavily, pruning back at least one-third. Lavender in full sun can be expected to grow vigorously each year, and vigorous growers need yearly attention to stay that way. (You can also take this opportunity to re-form your plants into the green mounds that are lavender’s signature shape.) With your hand pruners or pruning shears, aim to cut back all shoots at least one-third. Shears are less precise than hand pruners but save time and are a necessity for a lavender hedge.
Go heavier on older plants, but don’t cut down to leafless wood. You can’t rejuvenate older plants by cutting into old wood, but you can try to rejuvenate them by pruning to points just above the wood. A good rule of thumb is to count to the third node above the woody part and then cut just above it. If you are lucky, all three nodes and some hidden nodes buried in the wood will wake up and grow for you.
Beware Woody Growth and Winter
Your main goal in pruning lavender is to prepare it for the ravages of winter by reducing its size, weight, and density. This is a great reason to prune in autumn, just before frost and winter arrive.
As with so many plants, the biggest risk in pruning lavender is being too nervous to try! Not pruning lets a plant get large and woody, forming nooks and crooks that trap water, and thereby introducing several hazards:
- In summer, trapped water promotes rot in lavender's weak stems and wood.
- In late autumn, trapped water promotes an early frost, ending the growing season prematurely.
- In winter, trapped water can freeze, easily splitting out woody parts.
- A dense plant or one with sprawling wood is a weak target for snow load, which can deform or break plants.
Pruning Your Particular Variety of Lavender
While standard care will set any variety of lavender on a healthy and long-lived path, identifying your specific type of lavender, and timing pruning to that type, will help you get even more out of your efforts. There are three common types of lavender:
Lavandula angustifolia, or English lavender as it is commonly known, comes in many varieties, the most well known of which are Hidcote and Munstead. This “true lavender” has single, leafless stems and compact spikes of blossoms. It is generally low-growing and has a compact mounded shape. English lavender blooms in late spring to early summer, so if pruned lightly just after its first flowering, it will likely flower again in late-summer. After this second flowering, a full pruning—in late August—will prepare it for winter and encourage more blooms in spring.
Lavandin x intermedia, a hybrid of English and spike lavenders, also has many varieties; the most common are Grosso, Provence, and Giant Hidcote. The stems of lavandins are branched and longer than those of English lavender. Flower spikes are longer as well, and they have a graceful taper. While lavandins are also mounded in shape, these plants are usually larger, and the long stems tend to fan out from the center. Lavandins bloom later, in mid- to late-summer, so a full pruning after the long blooming season will prepare it for winter. Because of its long stems, you may need to prune up to one-half the plant’s size, but be extra careful not to cut the woody part of the plant.
Lavandula stoechas, sometimes called Spanish or French lavender, is the least hardy of the lavenders, and it blooms the earliest, in spring. Spanish lavender has a short, full flower spike with open “petals” at the top, distinguishing it from other types. Because of its relative fragility, prune this lavender lightly—never too close to the base—just after the first flowering, then follow up with gentle deadheading and shaping for the rest of the season. A slightly more vigorous pruning can be done in late-August to prepare the plant for winter and encourage a fuller plant in spring.