Lavender is a hardy, undemanding perennial with aromatic foliage and fragrant flowers that bloom all summer long. Versatile plants, lavenders are treasured for their beauty and fragrance as well as their culinary and medicinal uses. Lavender flowers can be used in arrangements during the growing season or dried for year-round use. Lavenders are often planted as a companion for roses, placed in perennial borders, or used as an edging for a cottage garden. Bees and butterflies flock to them. Problems with lavenders are generally minor and easily managed.
As they are native to the Mediterranean region, lavenders grow best in sunny, dry areas. Root rot is a fungal disease that thrives in wet, heavy soil. The leaves of the infected plant wilt and turn brown. Cut out and destroy diseased roots or plant parts. Water plants in the morning, taking care not to wet the foliage. Do not over water. Lavenders do better in soil that is slightly dry rather than too wet.
Spittlebugs or froghoppers are tiny insects that suck the sap from lavender plants. Their presence is detected as white, frothy blobs that appear on the stems and leaves of infected plants. The juvenile insects produce the "spit" as a hiding place where they can mature and feed undisturbed. Although unsightly, froghoppers don't pose a severe threat to lavenders and generally disappear by mid summer. You can direct a strong stream of water from a hose at infected plants to dislodge the insects.
The stems of lavender plants infected with this fungal spore begin to twist and turn brown. Tiny black spots appear on the stem. Pull out any infected plants and destroy them. Do not put them in your compost pile.
Lavenders can become leggy with woody, open areas developing in the middle of the plants. To keep lavender plants neat and well-shaped, prune them back by one-half immediately after blooming. Older plants do get woody over time and may need to be dug out and replaced.
Prevention is the best way to minimize problems and keep lavenders healthy. Plant lavenders in an area that receives at least six hours of sun per day. Lavender plants have shallow roots and do best planted in light, somewhat sandy, well-draining soil. Provide them with good air circulation to help keep the foliage dry and resistant to the growth of fungal disease. Use a soaker hose rather than an overhead sprinkler to keep the foliage dry. Mulch with pea gravel or sand rather than organic material. Keep the area around the plants free of garden debris to eliminate hiding place for pests.