To ensure lavender survives the winter and returns next year with new flowers, pruning the plant this month is essential, but it must be pruned correctly, or the whole plant will “need replacing. To determine exactly when to prune, look at the flowers of the lavender plant – by this time of year, they should be dull, and gray, and bees and other insects will no longer be buzzing around them. When most of the flowers change in this way, it’s the best time to prune the bush.
For later flowering lavenders, including Lavandula x intermedia like ‘Old English’, you should leave pruning until the following spring. The reason to do this is that it keeps the plant nice and fresh looking, and it avoids them getting leggy and bare at the base. Lavender, if not clipped back, can start looking gangly and mishappen and often needs replacing.
The golden rule with lavenders is when you’re pruning them, don’t cut into old woody growth. You don’t want to cut below this current season’s growth. You can see that it’s a slightly different colour. You can cut back as hard as you like into the new growth, but don’t cut below as it may not bounce back.
If not pruned, lavender will get woody, and the plant will look less attractive overall. There will also be less green growth in the following years, and flowering will be reduced. Furthermore, woody lavender plants are more likely to suffer frost damage or damage due to water logging. If you notice your lavender bush being woody or straggly, it’s usually best replaced as lavender won’t regrow well from older wood.