In Provence it is customary to cut the lavender only after it has bloomed - this is usually around mid to late August. However, faded lavender in Germany should no longer be pruned this late, otherwise it will develop less resistance to the winter cold.
When should you cut lavender after flowering?
Lavender should be pruned after flowering, around late July to early August, to encourage a second bloom and direct energy into plant growth. Only the dead shoots are removed. Older plants should be pruned less.
Cut lavender at the beginning of August at the latest
In German gardens, lavender is topiary in spring, before the first shoots appear. This is usually the case in April. It is better not to cut in the fall so as not to further weaken the plant before the onset of winter. Pruning after flowering is done towards the end of July, or at the beginning of August at the latest - then the lavender still has time to develop a second flower instead of putting its energy into seed production. Finally, the flowering also stops the formation of new shoots. When pruning flowers, only the dead shoots are removed.
Tips & Tricks
Older lavender should not be pruned nearly as much as young ones, because the plant does not sprout again from the lower, woody parts.