How to Prune Lavender (and Never Cut Into Old Wood)

Lavender does not die of old age in most gardens. It dies of being pruned politely — a light trim of the flower stalks each year, never into the leafy growth, until the plant is a tall gray framework with a thin green fringe on top that eventually splits down the middle.

The fix is counterintuitive: prune harder, earlier, and every single year. But there is one line you cannot cross.

The one rule

Take a plant and part the foliage at its base. You will find two distinct zones: bare gray-brown wood at the bottom, and soft leafy green growth above it.

Lavender is a subshrub, and unlike most garden shrubs it carries almost no dormant buds in that old wood. A stem cut below its lowest leaves has nothing left to grow from, so it simply dies — and if you shear the whole plant to that level, you kill the whole plant.

Everything else about pruning lavender is a consequence of this. The reason you prune every year is that a year of unpruned growth converts to permanent wood. Skip two or three years and the green zone has migrated so far up the plant that there is no longer enough of it left to cut into.

The two cuts

After flowering (the important one). Once the flower spikes fade in mid to late summer, shear the entire plant back by roughly a third — the spent stems plus a couple of inches of green growth below them. This is the cut that keeps the plant compact, and doing it in summer leaves plenty of time for the resulting new growth to harden before winter.

Early spring (cold climates only). Where winters are severe, wait until new growth is visibly breaking at the base, then trim off tips that were killed over winter and even out the shape. In mild climates this second cut is optional.

Shape it like a dome

Work around the plant rather than across it, and aim for a rounded mound that is a little wider at the base than at the top.

This is not aesthetic. A flat or dished top collects rain and snow, holds it against the crown, and is the usual reason an established plant splits open in the middle over winter. A dome sheds it. Hedge shears are fine for the bulk of the work on a large plant; switch to pruners wherever you are working close to the woody base.

Fixing a plant that has already gone leggy

Be realistic: you are unlikely to restore it. The bare wood will not reshoot, so there is no cut that brings a split, woody plant back to a compact mound.

What does work is replacing it from itself. In early summer, take 3-inch softwood cuttings from the non-flowering green tips, strip the lower leaves, and put them in a gritty, free-draining mix. They root readily — lavender is one of the easier plants to propagate this way — and you will have replacement plants within a season or two, at which point the old one can come out.