Prune dead foliage when the first green emerges in spring. It is difficult to tell the difference between dead branches and live ones before spring growth has started and lavender should never be pruned in winter or cut all the way to the ground. Try not to cut significantly into any live parts of the plant at this time.
Prune your lavender plants again when the flowers fade at the end of summer. This is the time to deadhead and shape the plants. Trim off the spent flowers and cut out some of the older branches on plants that are becoming woody. Plants larger than 3 feet in diameter can be cut back by about a third to prevent them from getting woody.
Water your lavender deeply when the soil is almost dry. Even in hot weather, lavender prefers infrequent watering. To help prevent over watering, grow lavender in well-drained soil in full sun.