Fungus on Lavender Roots

Root Rot

• Phytophthora root rot and Pythium root rot are the two types of fungal infections common to the lavender plant. Phytophthora cinnamomi is one of the more common types. Black root rot (Thielaviopsis basicola) creates black lesions (sunken areas) on lavender roots. These infections often lead to stunted foliage, slowed growth and dead roots, which prevent adequate uptake of water and nutrients. In the case of lavender, leaves may turn yellow or gray and wilt permanently. Roots appear soft and blackened and break easily. Keep an eye out for root rot during wet, rainy seasons.

Treating Root Rot

• If root rot has infected a garden bed, remove heavily infected plants immediately to prevent the disease from spreading to nearby plants. You can give these removed plants a second chance by attempting to remove rotted roots. Carefully snip off diseased sections with sterilized scissors. Much of the root system may have to be removed. Dip remaining roots in fungicide. Replant into fresh or sterilized soil that is well-draining and provide a clean, sterilized pot.

Preventing Root Rot

• Root rot can occur in plants that have been watered too heavily or lack adequate drainage. Standing water of melting snow piles around a lavender plant can also make it fall victim to the disease. Apply coarse sand around the plant’s base to encourage drainage and weed the garden bed thoroughly around the plant to promote air circulation. When growing lavender in pots, a slight crowding of the roots is beneficial as it keeps them dry. Too much soil in a container can lead to lingering wetness and fungal disease. Use a container just 1 or 2 inches larger than the root ball and place gravel at the bottom of the pot to ensure soil dries out between watering.

Lavender Growing Tips

• Lavender is a true Mediterranean plant that is tolerant of drought and thrives in hot, dry weather and somewhat sandy soil. Adequate drainage and airflow is essential for a healthy plant. Plant in soil that is loose and light. During establishment, provide plenty or water, but once roots are established, allow the top layer of soil to dry out between watering. An ideal time to plant lavender is in the fall because it establishes faster and flowers pleasantly come springtime. Select large, well-established plants for fall planting. If planting in spring, you can select smaller plants as they will have more time to establish their roots.