Locations Suitable for Growing Lavender
Lavenders originated around the Mediterranean in poor, rocky soils and mild coastal climates; consequently, most lavender species prefer a Mediterranean-like climate; where summers are long, sunny, and warm, and where winters are mild. Lavender requires full sun to grow and produce well, but areas with extremely hot summers and/or warm winters may not be suited to commercial lavender cultivation such as a USDA Hardiness Zones 7 or 8. Extremely hot weather can hinder growth and reduce lavender quality and it also requires a cold period to induce good flowering. Some lavenders can be grown in USDA Hardiness Zones 5 and above however, Lavender grown in well-drained soils can withstand colder winters. Lavender does best in a low humidity climates, and if grown in areas of high humidity it is far more prone to fungal diseases. If grown in a more humid environment, plant spacing should be increased.
Excellent drainage and full sun is crucial to the survival of lavender plantings no matter what climate lavender is cultivated.
Most lavender in the world is grown on stony, calcareous soils with a pH range of 6 to 8. Lavender does not grow well in clay soils, or in saturated soils. particularly during the late fall, winter, and early spring, when the plants are dormant. If soil saturation is in question it is recommend that the lavender be planted on mounds or berms. Lavender can be a long-lived perennial, with a typical productive life of about 10 years, although plants have been known to live for 20 years.
Establishing Lavender Plants
Propagating: Lavender is best propagated from softwood cuttings of standard types. Cuttings results in new plants that are clones of the parent plant, thus guaranteeing that new plants maintain the true properties. Seed may not maintain true to type, and lavender seed is sterile. Lavender is commonly planted in rows or hedges, plants grown from seed will have significant variability in color and plant size, thus creating an uneven and unattractive lavender. Lavender grown for oil, or dried stems, should never be grown from seed. It should also be noted that some lavender varieties are harder to propagate than others. Cuttings should be 2 ½ to 3 inches in length. The leaves from the bottom inch of the cutting should be removed. Dip the base of the cutting in a rooting hormone and place into a sterile planting soil. Rooting typically takes three to five weeks and there should be about a 90% survival rate.
Another method for propagating lavender is by layering. In the spring, select an outside branch and bend it down to the ground. Measure 8 to 12 inches from the growing tip. Remove all leaves and foliage from this section of the branch, leaving about 6 inches of foliage at the end of the branch. Dig a 3 to 4 inch deep hole, moisten the area of the branch that has been defoliated, and sprinkle with a rooting hormone. Pin the branch down in the ground, and then cover the branch with soil, leaving the end with foliage exposed. Keep the branch watered and once it has rooted, cut it off from the parent plant and replant.
Most people find it easier and cheaper to buy lavender plants, verses propagating lavender. Lavender plants can be purchased at all growth intervals, from nurseries and garden stores. If purchasing a large quantity of lavender plants, it is best to locate a wholesale supplier of lavender. There are many lavender cultivators, and because many lavender plants look alike at early stages of growth, it is somewhat common for plants to be misidentified. Therefore, purchase lavender plants from wholesale nurseries who have a good reputation for high quality and properly identified plants. Inquire if the lavender herb farm guarantees the plant variety. Lavender is commonly grown in plug trays of 72 or 128 cells per tray. Some purchase plug trays and transplant directly from the tray to the field. While others prefer to purchase larger plants in 2 1/2- or 4-inch pots. The plugs will obviously be the most economical pricing, however, one advantage to purchasing larger plants is that survival rates will be greater. Lavender plants purchased in pots, should be well-rooted, and not plugs recently transferred to pots. Also, make sure the lavender plants are not root-bound, yellow, or wilted.
Planting: Before transplanting it is best to let the plants adapt to the environment by placing them by the fields to be planted, for several days prior to transplanting, keeping them moist and in full sun. In mild climates for instance below Zone 6 fall is the preferred time to transplant lavender. Plants planted in the fall will have more established root systems and be better able to thrive hot, dry summer days.
In the higher Zones, spring planting is best.
Plant spacing is important to consider when laying out the fields. Spacing the plants has a great deal to do with the end product you intend for the lavender. Growing lavender for oil production, plants can be spaced closer than if your intent is to cut the lavender by hand and create dried lavender bundles. Spacing rows less than 6 feet apart makes hand harvesting and other work difficult as the plants reach maturity. Spacing plants within rows closer than 3 feet apart also makes hand harvesting more difficult, as the plants grow, the stems from adjacent plants become intertwine and make it difficult to grasp the stems, for cutting the bunches.
Typically, lavender should be planted on 3 foot centers with the rows on six foot centers. This allows for mowing between the rows verses extensive weeding. However, some growers like to plant relatively densely within rows. Denser plantings produce larger harvests in the first year or two, and planting more densely helps limit the plants mature size, which reduces the likelihood of older plants breaking apart in the middle. Spacing of 5 feet between rows and 30 inches between plants results in approximately 3,400 plants per acre, and a spacing of 6 feet and 36 inches results in approximately 2,400 plants per acre.
Before planting, it the ground should be properly prepared. Weed should control should be established, and the field tilled to a depth of at least 10 inches. Any soil additives such as lime should be applied prior to planting. Lavender does not compete well with weeds, and weed infestations will decrease the yield and quality of lavender stems, flowers, and oil. The best way to control weeds in lavender is to not allow weeds to become a problem from the start. If weeding is done diligently after planting, weed control will get easier with time as the lavender plants mature, they will shade weeds within the row.
Many growers use a black landscape fabric as a weed barrier on each row to reduce future weeding. Holes are burned into the weed fabric barrier at the desired spacing, using a propane heated burner. Planting is done using a small garden positioning the plant at or slightly above the level of the surrounding soil. In areas with sufficient rainfall, watering is necessary for at least three days after planting. However, in those areas without sufficient rainfall an irrigation system should be in place at the time of planting.
Pruning: Pruning is essential for the health and production of lavender plants. It should begin with newly planted plants by removing the flower stems for the first year. This will improve plant vigor and allow the plant to develop better foliage and root system. Lavender that is not pruned, will break open in the middle, becoming woody, ugly, and unproductive. Pruning of the flowering stalks and upper growth points stimulates development of new flowering buds for the next year’ production.
Lavender should be pruned aggressively, but it is important not to prune back into old wood, as this may hinder the reproduction of new shoots, and a lavender plant can sometimes be killed by over pruning into the old wood. The old wood is gray to black in coloration. It is best is to leave a couple of the current season’ wood growth. Pruning should be done in the fall and in areas with harsh winters it is best to prune in the early fall before the first hard frosts. Hand shears can be used for pruning or for larger farms, gas powered hedge trimmers may be utilized.
Diseases and Insects
One of Lavender’s great properties is it has relatively few insect, animals and diseases that are harmful to the plant. It is though the camphor found in lavender plants is one of the contributing factors which cause it to be relatively pest free. However, there are a few pest such as Spittle bugs which are a common pest of lavender and appear in spring but are rarely a threat to the plant. Aphids are another pest but seldom directly affect the plant, however, it is a source for spreading Alfalfa Mosaic Virus (AMV) a common disease of lavender. cause serious damage and primarily appear in the spring.
Aphids can spread Alfalfa Mosaic Virus in lavender. Bright yellow patches develop form on the plant, and will not typically kill plants, but will reduce their health and production. Even though the presence on the plant is minorthe virus is present throughout the plant. Therefore, once a plant has become infected with AMV, it should be removed and burned. Not only is the virus is spread by aphids, but it can also be spread by contaminated tools, and hands therefore, it is important the infected plants be destroyed immediately.
One of Lavender’s greatest enemies is root rot. The roots of plants grown in poorly drained soils are infected and begin to rot, then subsequently die. Planting in raised mounds, as mentioned earlier, can help. However, it is important to realize that the fungal organisms will continue if the environmental conditions that favor their growth are not altered.
Also see: Harvesting Lavender