Usually, old lavender is replaced. However, many of us grow attached to the plants we care for. Perhaps they were a gift, or were planted by a person we cherish. We’re loathe to just pull it out without even trying!
Risks of hard pruning on lavender
The plant might not survive. This isn’t due to any particular mistake or bad luck. It’s just that lavender doesn’t cope with hard pruning well.
New branching requires lots of sap circulation.
Cutting leafy tips off and leaving only woody stems behind stops sap circulation.
Small sprouts and buds can’t pull nutrients and water up and die off.
Staged pruning in a nutshell
Staging the hard pruning over three years (or even four) makes it easier on the plant.
The goal is to strike a delicate balance.
On one hand, hard pruning is necessary to reduce shrub size.
On the other, you protect the plant from severe pruning shock.
You can trigger new shoots from around the base by following these steps:
Let light enter to the center of the plant.
Wait for sprouting along older woody stems, without cutting their leafy bits off at first.
When sprouts are vigorous enough, shorten older stems to reduce and rejuvenate the shrub.
How to hard-prune lavender
An initial, light, maintenance pruning is performed on the entire shrub.
Every year after that, one third of the long, woody branches are cut back to the trunk.
This deals with normal growth and shortens the “active tips” of the plant.
It will help promote branching out.
After that, while still in year 1
Cut one in three stalks back all the way back to the trunk. This creates holes in the shrub, which lets light reach the center.
For each remaining stem, cut growth back to leave only 2-3 inches of green leaves (7-10 cm). Practically, this means cutting tips off but leaving 4-5 pairs of leaves on each stem.
Normally, a few shoots will emerge from the old base. They grow slowly.
This being the following year, cut off half of the remaining older, leggy shoots back to the trunk. This is the second “batch” of stems to be cut back totally.
Trim all new, young shoots to half their new growth. These are your future lavender stems so you want to make sure they branch out a lot.
Keep pinching or cutting the tips off these shoots every time they reach four or five new pairs of leaves.
Year 3 – wrap up the last woody stems
Again, more new shoots emerge, and the previous year’s shoots have branched out.
Cut back to the trunk any remaining old, woody stems.
You can trigger new shoots from around the base by following these steps:
Normally, a few shoots will emerge from the old base. They grow slowly.
Remove enough bark to reveal the green, live layer of cambium cells underneath.
