Lavender generally thrives in lean, well-draining soil and does not require much, if any, fertilizer. In fact, too much fertilizer, especially those high in nitrogen, can be detrimental to lavender.
Here's why and what to consider:
Why Less is More for Lavender:
-
Native Habitat: Lavender's natural habitat is typically rocky, poor, and alkaline soils of the Mediterranean region. These soils are not rich in nutrients. Lavender has evolved to thrive in these conditions.
-
Encourages Leggy Growth, Reduces Flowers/Scent: High nitrogen fertilizers promote leafy green growth at the expense of flowers and the concentration of essential oils. This can lead to lanky, "leggy" plants with fewer blooms and a weaker, less desirable fragrance.
-
Increases Susceptibility to Rot: Lush, soft, nitrogen-fueled growth is more susceptible to fungal diseases and rot, especially in humid conditions or if the soil is not perfectly drained.
-
Stress on Roots: Excess nutrients can "burn" delicate lavender roots.
When to Consider Fertilizing (and what to use):
In most well-prepared garden soils, established lavender needs no supplemental feeding. However, there are a few specific situations where a very light application might be beneficial:
-
Poor, Extremely Infertile Soil: If your soil is truly depleted of nutrients (a soil test would confirm this), a very light, balanced, slow-release fertilizer or compost could be applied sparingly.
-
Container-Grown Lavender: Plants in pots have a finite amount of nutrients in their potting mix, which can get leached out over time.
-
Recommendation: Use a very dilute, balanced liquid fertilizer (e.g., 5-10-5 or 5-10-10) at half or quarter strength, or a slow-release granular fertilizer formulated for herbs or Mediterranean plants, applied once in early spring as new growth begins. Do not fertilize after mid-summer.
-
-
Newly Planted Lavender (rarely needed): If your planting hole was amended with some compost (and you have well-drained soil), additional fertilizer is usually not necessary. The focus for new plants is root establishment.
What Kind of Fertilizer, If Any:
If you feel your lavender needs a boost:
-
Compost: A thin layer of well-rotted compost applied around the base of the plant (but kept away from the crown to prevent rot) in early spring can provide a gentle, slow release of micronutrients without overwhelming the plant.
-
Balanced, Low-Nitrogen Fertilizers: Look for fertilizers with a higher phosphorus (P) and potassium (K) content relative to nitrogen (N). Examples include NPK ratios like 5-10-10 or even 0-10-10.
-
Organic Options: Bone meal (for phosphorus) or kelp meal (for trace minerals) can be very lightly worked into the soil around the plant in spring.
-
Alkaline Soil Additives (if pH is low): Lavender prefers slightly alkaline to neutral soil (pH 6.5-7.5). If your soil is acidic, adding agricultural lime or wood ash can help raise the pH and provide calcium, which lavender appreciates. This isn't technically a fertilizer but helps nutrient availability.
When to Apply:
-
Early Spring: If you decide to fertilize, the absolute best time is in early spring, just as the plant is breaking dormancy and putting on new growth. This supports flower production.
-
Never in Late Summer or Fall: Fertilizing late in the season can promote tender new growth that won't harden off before winter, making the plant more susceptible to cold damage.
The Golden Rule for Lavender and Fertilizer:
When in doubt, don't fertilize. Lavender is much more likely to suffer from over-fertilization (leading to leggy growth, weak scent, and rot) than from a lack of nutrients, especially when planted in appropriate, well-draining soil in full sun. Focus on excellent drainage and plenty of sunlight, and your lavender will likely thrive.
Lavender Farm in Door County Wisconsin. You can buy lavender products online at islandlavender.com