How to Prune French lavender?
Shorten flowered shoots to about 1.5–2.5 cm from the previous year's growth. Prune after flowering has finished.

French lavender · Lavandula dentata
Also known as: sweet-scented lavender
Grow in well-drained soil in a sheltered, sunny position. See lavender cultivation for further advice
Shorten flowered shoots to about 1.5–2.5 cm from the previous year's growth. Prune after flowering has finished.