Lavender Fertilizer: When and How to Use It

Many gardeners believe lavender thrives on neglect. While these plants are adapted to nutrient-poor conditions, this doesn’t mean they require no nutrients. A strategic application of the right fertilizer can support robust growth and abundant flowering. Understanding that lavender is a light feeder is the first step toward providing optimal care without causing harm.

When to Fertilize Lavender

The most common time to provide nutrients is in the spring, just as new growth begins to appear. For newly planted lavender, incorporating a small amount of fertilizer at planting time helps establish a strong root system. This initial feeding with a slow-release product ensures a gentle supply of nutrients as the plant settles into its new environment.

Container-grown lavender has different requirements. Nutrients in pots are depleted more quickly due to the limited soil volume and frequent watering, which leaches minerals from the potting mix. For these plants, a light annual feeding in the spring is beneficial to replenish lost nutrients for the upcoming growing season.

Established, in-ground lavender in healthy soil often does not need any supplemental fertilizer. However, if your soil is exceptionally sandy or poor, a single application in the spring can be helpful. Avoid fertilizing any lavender in the late summer or fall, as this can encourage tender new growth that is susceptible to damage from winter cold.

Choosing the Right Fertilizer

Selecting the appropriate fertilizer is based on lavender’s need for low nitrogen. High-nitrogen formulas encourage the plant to produce lush, green foliage at the expense of its flowers. The goal is to support flowering and strong stems, not excessive leaf production.

The best options are slow-release, organic fertilizers that provide nutrients gradually. A simple application of well-rotted compost, spread about an inch thick, can offer sufficient nutrients for an entire year. Bone meal is another excellent choice, as it is high in phosphorus, a nutrient that supports root development and flower production without adding excessive nitrogen.

Certain fertilizers should be avoided entirely when caring for lavender. High-nitrogen products, such as lawn fertilizers or aggressive, all-purpose chemical plant foods, can be detrimental. These can deliver an overdose of nutrients that leads to weak growth or can even damage the plant’s root system.

How to Apply Fertilizer

The method for applying fertilizer to lavender is designed to prevent crown rot. The most effective technique is top-dressing, which involves lightly sprinkling the chosen amendment on the soil surface around the plant. When applying granular products like bone meal or compost, keep the material away from the base, or crown, of the plant to avoid trapping moisture.

After spreading the fertilizer, gently scratch it into the top inch of soil with a hand rake. This action helps integrate the nutrients into the root zone where they can be accessed by the plant and prevents the fertilizer from being washed away.

Following the application, water the area lightly. This helps to activate the fertilizer, allowing it to begin breaking down and releasing its nutrients into the soil. A light watering is sufficient to start this process without waterlogging the plant.

Risks of Over-Fertilizing

Giving lavender too many nutrients, especially nitrogen, leads to disappointing results. One of the most common signs is the development of long, leggy stems and an abundance of green leaves with very few flowers. The plant directs its energy into producing foliage rather than the fragrant blooms that are its main attraction.

This lush growth is often weak and floppy, unable to support its own weight. This can cause the plant to splay open, creating an untidy appearance and making it more susceptible to physical damage. The structural integrity of the plant is compromised, detracting from its natural, mounded shape.

Excess nutrients can also diminish the signature fragrance of the lavender. The concentration of aromatic oils in both the flowers and foliage may be reduced, making the plant less fragrant. Furthermore, over-fertilized plants are more vulnerable to health issues like fungal diseases and root rot, particularly during wet winter months.