How to Grow and Care for French Lavender

French lavender (Lavandula dentata), also called fringed lavender, is identified by its gray-green leaves with square-toothed edges. The plant produces pale lavender-blue flowers on short spikes and emits a fragrance with notes of camphor or pine, which is less sweet than its English counterpart. This variety has specific care requirements that differ from other lavenders.

Ideal Growing Conditions for French Lavender

Sunlight

French lavender must be planted in a location that receives a minimum of six to eight hours of direct sunlight daily. This is required for healthy growth, abundant flowering, and developing its characteristic aroma. Plants in shadier spots tend to become leggy and produce fewer flowers, while its gray foliage helps it cope with intense summer heat.

Soil

This plant demands soil with excellent drainage, as its root system is susceptible to rot in wet conditions. Sandy or gravelly soils are ideal because they allow water to move away from the roots quickly. Heavy clay soils retain moisture and should be amended, or the lavender should be grown in raised beds. Container planting is an excellent alternative, providing complete control over the growing medium. An alkaline or neutral soil pH between 6.0 and 8.0 is also preferred.

Watering

French lavender is drought-tolerant, and overwatering is a common mistake. The correct approach is to water deeply but infrequently, allowing the soil to dry out completely between sessions. Young plants may need water every two to three weeks during a dry summer. Once established, the plant requires very little supplemental water and can often thrive on natural rainfall alone.

Temperature and Humidity

French lavender performs best in warm, dry climates with low humidity. High humidity can lead to fungal diseases, so good air circulation is a priority. This species is less cold-hardy than English lavenders and is suited for USDA hardiness zones 8 through 11. It tolerates brief frosts but may not survive sustained temperatures below 20-23°F (-5 to -6°C), especially in wet winter soil.

Pruning French Lavender

Regular pruning is necessary to maintain the health and appearance of French lavender. Without it, the plant can become woody and sparse at its base. This annual trimming encourages a compact, bushy shape and stimulates new growth, which leads to more abundant flowering.

The best time to prune is in late summer or early fall, after the main flowering period has concluded. This allows the plant to recover before winter, as pruning too late can encourage tender new growth that is vulnerable to cold damage. A light trim in the spring can also be done to shape the plant.

When pruning, remove approximately one-third of the plant’s height, focusing on the green, leafy growth. Make cuts above leaves or side shoots, as the plant will regrow from these points. Avoid cutting into the old, brown wood at the plant’s center, as this hard wood may not produce new shoots and can kill the plant.

Overwintering and Frost Protection

French lavender is less cold-tolerant than other varieties and requires winter protection in cooler climates. Hard frosts and freezing temperatures can damage the plant, especially when combined with wet winter soil.

For container-grown plants, bring them indoors to a sunny, south-facing window that receives at least six hours of light. Reduce watering significantly during this dormant period, allowing the soil to dry out completely. This protects the plant from both cold and root rot.

For lavenders in the ground in marginal zones (like USDA zone 8), apply a thick layer of light mulch like straw or pine needles after the first hard frost. This insulates the root ball. Avoid heavy mulches against the stem, as this can trap moisture and cause rot.

Common Problems and Solutions

Root rot is a frequent issue caused by overwatering or soil that does not drain well. Symptoms include yellowing leaves, a wilted appearance despite wet soil, and a soft, mushy base. Prevention requires following the soil and watering guidelines outlined earlier.

In humid regions, fungal issues like powdery mildew can appear as a white, dusty coating on the leaves. This is often a result of poor air circulation. To mitigate this, provide ample spacing between plants for airflow and water directly at the base to keep the foliage dry.

A lack of flowers is often linked to correctable environmental factors. The primary cause is insufficient sunlight, as the plant needs at least six hours of direct sun to set buds. Improper pruning can also be a factor, as trimming too heavily late in the season removes the growth that would produce the next year’s flowers.