Lavender is native to the hot, dry climate of the Mediterranean but has become one the favorite plants of gardeners from all over. Appropriate planting, preparation and siting is critical to the longevity of lavender.
Success in growing lavender depends on growing conditions and the variety you choose to grow. Though lavender will tolerate a wide range of garden conditions, it prefers well drained soil and full-sun. There’s a big difference between tolerating site conditions and thriving in them so try to place them appropriately. A lean soil will encourage a higher concentration of oils. Alkaline soil will enhance lavenders fragrance. Zone 5 it about its limit. You can grow lavender here but the health of the plant will depend more on the weather, especial winter conditions. Cold, harsh winters will occasionally kill off lavender. If you are going to grow lavender in zone 5 be sure to plant it out of the wind and if possible against a sunny wall where there is, in addition to wind protection, added warmth. Where the ground freezes, apply mulch around the plant during the winter. Wet humid summers are also troublesome. In fact, wet roots will kill lavender more than cold. Make sure that the plant has ample room for airflow.
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.
In the spring lavender should be pruned to keep them well shaped and to encourage new growth. 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. In colder climates, wait to prune until new grown is visible.
Containers are an ideal way to add lavender to your garden. In colder climates, growing plants in containers allow you to take them indoors during the winter months. Use well drained soil for the pot and place a couple inches of soil at the pots base for additional drainage. 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.
A major reason lavender is so prized is that the flowers keep their fragrance when dried. For best drying results, harvest the flowers as the buds first begin to open. Hang in small bunches upside down in a warm spot with good air circulation. Besides being beautiful and aromatic, lavender flowers are also edible.
Unfortunately even if you do everything right and your lavender plants appear happy, the genus is generally not long lived and most lavender plants begin to decline after about 10 years.