As with most plants, your success in growing this coveted plant will depend both on what kind of growing conditions you can provide and which varieties you select to grow. Lavender plants will tolerate many growing conditions, but it thrives in warm, well-drained soil and full sun. Like many plants grown for their essential oils, a lean soil will encourage a higher concentration of oils. An alkaline and especially chalky soil will enhance lavenders fragrance. While you can grow lavender in USDA Zone 5, it is unlikely you will ever have a lavender hedge. More realistically you can expect to have plants that will do well when the weather cooperates and to experience the occasional loss of a plant or two after a severe winter or a wet, humid summer.
Lavender is a tough plant and is extremely drought resistant, once established. However, when first starting you lavender plants, don't be afraid to give them a handful of compost in the planting hole and to keep them regularly watered during their first growing season.
It is dampness, more than cold, that is responsible for killing lavender plants. Dampness can come in the form of wet roots during the winter months or high humidity in the summer. If humidity is a problem, make sure you have plenty of space between your plants for air flow and always plant in a sunny location. Areas where the ground routinely freezes and thaws throughout the winter will benefit from a layer of mulch applied after the ground initially freezes. Also protect your lavender plants from harsh winter winds. Planting next to a stone or brick wall will provide additional heat and protection.
Although lavender plants get regularly pruned simply by harvesting the flowers, to keep them well shaped and to encourage new growth, a bit of spring pruning is in order. The taller varieties can be cut back by approximately one-third their height. Lower growing varieties can either be pruned back by a couple of inches or cut down to new growth. If you live in an area where lavender suffers some winter die-back, don't even think about pruning your plants until you see some new green growth at the base of the plant. If you disturb the plants too soon in the season, they give up trying.
You can always grow your lavender in pots and move it to follow the sun or even bring it indoors for the winter. Keep in mind that although lavender has a large, spreading root system, it prefers growing in a tight space. A pot that can accommodate the root ball with a couple of inches to spare would be a good choice. Too large a pot will only encourage excessive dampness.
Insure that the pot has plenty of drainage. To prevent water pooling in the pot, place about an inch of loose gravel at the bottom. Rot root is one of the few problems experienced by lavender plants. Use a loose, soilless mix for planting and remember that container grown lavender will require more water than garden grown plants. How much more depends on the environment and the type of pot. Water when the soil, not the plant, appears dry and water at the base of the plant to limit dampness on the foliage. Compact varieties make the best choices for containers. Some to try are L. angustifolia ‘Nana Alba’ and Spanish lavender (L. stoechas subsp. pedunculata)
How will you use this lovely lavender you'll be growing?