When you make the mistake of cutting woody lavender stems, those branches will not grow back. The bare wood lacks the ability to sprout new shoots, so any stem cut below its green foliage dies off for good. This creates ugly gaps in your plant that nothing will fill.
I learned this lesson the hard way during my second year of growing lavender. I wanted to reshape an overgrown plant, so I cut several stems down to their thick brown bases. Two years later, those stems remained dead stubs while the rest of the plant grew around them.
The problem with lavender bare wood pruning comes down to plant biology. As lavender stems age, they go through a process called lignification. The soft green tissue hardens into rigid brown wood. During this change, the stem loses its meristematic tissue, which are the special cells that let plants produce new growth.
Most woody shrubs keep dormant buds hidden under their bark. Roses and forsythia can sprout fresh shoots from bare wood. But old lavender stems lack this ability. The plant evolved on rocky hillsides where saving energy beat growing back from damage.
Maryland extension experts warn that severe cutting can kill lavender. Once you remove all the green growth from a section, that part cannot bounce back. The roots may stay alive for a while, but the stems never grow back. I watched my neighbor make this exact mistake last summer with sad results.
Before you make any cuts, find the transition zone where green tissue meets old wood. Part the foliage and look at the lower stems. You should see a clear line where silvery-green bark changes to brown. Always keep your cuts at least two inches above this line to stay safe.
Try the scratch test if you cannot tell whether a stem has life left in it. Use your fingernail to scrape a tiny patch of bark off the questionable area. Green tissue underneath means the stem can still support growth. Brown or tan tissue tells you that section has died and will not come back.
When you inherit an old plant with lots of bare wood, you face a tough choice. You can leave it alone and accept its sparse look, or you can replace it with a young plant. Trying to cut it back hard will only make things worse by killing more of the remaining live growth.
Read the full article: How to Prune Lavender Plants for Better Growth
