With its soft purple flower spikes and signature scent, lavender is a popular container or landscape plant. A perennial herb in zones 5 to 7, lavender is best known for its use as a potpourri or moth-repelling sachet, but it has medicinal and culinary uses, as well. According to the University of Maryland Medical Center, lavender "may slow the activity of the nervous system, improve sleep quality, promote relaxation, and lift mood in people suffering from sleep disorders."
Conduct a soil test. Lavender prefers a soil pH between 6 and 8.3. Raise soil pH by adding sulfur or ammonium sulfate. Both of these chemicals are available at home and garden centers. Peat moss also helps to buffer low pH. To lower soil pH, use garden lime, coffee grounds, compost or shredded leaves.
Till the bed to a depth of 1 foot to loosen compacted soil. Rake and level the planting area.
Dig a hole at least twice the size of the plant's root ball. Set the plant into the hole and refill, gently tamping down the soil to secure the plant in its new location. Water thoroughly at the soil level.
Space plants at least 18 inches apart. In humid locations, space the plants at least 24 inches apart. Lavender is subject to a mold that spreads more easily in damp conditions. Adequate spacing allows sun and air to pass between the plants, keeping mold at bay.
Water early in the day, using a soaker hose or drip irrigation. Water new plants weekly. After plants have established, water only when the soil is dry to a depth of 4 inches.
Prune established lavender plants in early spring. Using clippers or a hedge trimmer, remove about 1/3 of the plant's top growth. Remove and discard any damaged or weakened stems and rake away fallen leaves and debris.