Lavender (Lavandula spp.) is a shrubby, evergreen member of the mint or Lamiaceae family, noted for its aromatic purple flowers and green or gray-green, needlelike leaves. Native to the Mediterranean, it is suitable for herb gardens, mixed borders, containers and even low hedges. Generally, lavender flowers in late spring or summer, but flowering times vary widely according to species, variety and, sometimes, cultural practices. Plants that do not flower, or flower weakly, can usually be strengthened by a change in site or soil conditions.
Order of Bloom
Different lavender species bloom at slightly different times in very late spring and summer. The earliest lavenders, appearing as early as midspring, are species and hybrids of Spanish lavender, sometimes also known as French lavender (Lavandula stoechas), hardy in U.S. Department of Agriculture plant hardiness zones 8 through 9, with deep purple flowers, each topped by a pair of erect, earlike purple petals. The latest blooming lavenders, often appearing in midsummer, are species and varieties of English or lavandin lavender (Lavandula angustifolia), hardy in USDA zones 5 through 8. These are noted for their gray-green foliage.
Lavender Growing Conditions
To retain good health and bloom abundantly, lavender must receive at least six hours of full sun per day. The plants also require extremely well-drained, low-fertility soil, like sandy loam, to perform best. Growing lavender on a gentle slope will aid drainage as well. The plants are also highly susceptible to winter damage in cold winter areas, so plant in protected spots and make sure to select varieties that are reliably hardy in the specific USDA plant hardiness zone.
Healthy lavenders can often be induced to rebloom later in the growing season, providing a second harvest of the fragrant flowerheads. The shrubby plants bloom only on new wood, so either harvest the flowerheads for arrangements or crafts, or trim off spent flowerheads when blooms fade. Trim back stems by about one-third. This helps shape the lavender but also stimulates new growth and eventual rebloom. If pruned in early summer, lavender plants situated in areas with long, warm growing seasons may bloom again in early fall. Watch for signs of new growth to see if this is happening.
Troubleshooting Lavender Problems
If lavender fails to bloom or blooms sparsely, the obvious culprits are lack of light or poor soil conditions. Root rot due to heavy, clayey, water-retentive soil is common. Fix it by removing the plant from the bed and amending the soil with equal amounts of compost. After replanting the lavender, mulch with fine stone, which aids drainage. If soil amendment is impossible, create a raised bed filled with half soil and half compost. Older plants may produce few or no flowers. If the plant is more than five years old, it should probably be replaced.