Outdoor Planting – Plant lavender in the spring after the last frost or in early summer. If late summer or fall, then plant at least 8 weeks prior to the first frost so roots can get established. Choose a location to plant your lavender that has full sun and well-drained soil. Site preparation related to soil issues and weed management needs to be addressed prior to planting.
Lavender does not tolerate excessive soil moisture, especially during the winter months. Planting on a slope and/or on raised beds will increase drainage. Since lavender grows best in soils with low to moderate fertility you don’t need to amend the soil with organic matter before planting. However, if you have poorly drained clay soils then amend those soils with organic matter such as compost. Perform a soil test to check for pH. If the soil pH is less than 6.5 then add lime to raise the pH to around 7.0. Add sulfur to lower the pH to 7.0 if the soil pH is greater than 7.5.
Lavender are poor competitors with weeds in terms of growing space, sunlight, water and nutrients. Weeds negatively effect lavender growth and health, and ultimately the quantity of plant material available for harvest. A weed control strategy should include tilling before planting, followed by subsequent tilling and/or hand weeding. An alternative method is covering the soil with water permeable woven weed fabric.
When planting multiple lavender space them 2 to 4 feet apart depending on the variety and planting objective. In general, English lavenders are spaced 3 feet apart and larger Lavandin lavenders 4 feet apart. Narrower spacings are used for forming a hedge. Well spaced plants promote good air circulation between plants and lessen the opportunity for disease. If planting lavender through woven weed fabric then burn a hole in the fabric using a template and a hand held butane torch. The hole is burned rather than cut to prevent the woven fabric from fraying. A drill with an auger attachment works well for digging planting holes. The planting hole should be two times deeper and wider than the lavender’s root ball.
Prior to planting add 1/4 cup of bone meal to the planting hole and mix thoroughly with the soil. Bone meal, an organic fertilizer, has slow release phosphorus which will promote root development. In addition, cut about 1-2 inches off the branch tips to remove apical dominance and promote branch growth, thus creating a more bushy plant. Also, during the first growing season remove flowers to re-direct the plant’s resources to root growth.
Lavender should be planted no deeper in the ground than it sat in the nursery pot or with the top of the root ball even with the soil line. Soil should be back filled and firmly pressed around the plant, and then watered to compress the soil to remove air pockets. Lastly, a 2-3 inch layer of crushed rock (e.g., 5/8 minus gravel) or pea gravel should be added to enhance drainage, keep the soil and plant warm during the winter, and provide weed control. Avoid using compost or other organic mulch that could retain water and cause root rots or lead to other diseases.
If you are planting lavender growing in 1 or 2 gallon pots then you will need to burn a hole in the weed fabric the size of the root ball and add 1/2 to 1 cup of bone meal.
Outdoor Container Planting – When planted in pots lavender prefers a tight space even though it has a large spreading root mass. Pots that are too large encourage excessive dampness and thus increase the opportunity for disease. Make sure the pot has a sufficient number of holes in the bottom to provide good drainage, and always water from below. Use a well-draining soil such as Sunshine Mix #4, cactus potting mix, or your favorite premium potting soil mixed with 50% perlite. Remember, lavender planted in outdoor containers grow best by addressing all five basic requirements. Don’t be discouraged if your lavender does not thrive as a potted plant. Lavender prefers growing outdoors in the ground rather than the limited existence within a pot.