Shear off the lavender plant in the spring when the plant begins growing again. Remove approximately one-third of the length of each stem, using pruning shears, to encourage extra blossoms.
Sprinkle 1/2-cup bone meal onto the soil around a lavender plant after pruning. Work the bone meal in well with a hand fork and moisten the soil thoroughly. The bone meal, although not mandatory, will help increase nitrogen levels in the soil, keeping the lavender plant thriving.
Deadhead the spent lavender blossoms throughout the growing season to encourage the plant to bloom for a longer period. Cut the spent blossoms off immediately under the flowers.
Prune lavender a final time in the autumn to prepare it for the next growing season. Cut back the stems to leave only approximately 2 inches of green on the stems. This late-season pruning will encourage fuller growth and more blossoms in the next growing season.