Lavender thrives in lean, well-draining soil. This plant naturally has low nutrient requirements, needing minimal, if any, fertilization. Over-fertilization is a common error that often proves more detrimental to lavender’s health than under-fertilization.
Understanding Lavender’s Nutritional Needs
Lavender plants prefer soils that are low in nitrogen and moderate in phosphorus and potassium. Nitrogen primarily promotes leafy growth, and an excess can lead to abundant foliage at the expense of flower production. Too much nitrogen can also make the plant more susceptible to pests and diseases by encouraging soft, succulent growth.
The plant’s ability to absorb nutrients is also influenced by soil pH. Lavender prefers soil that is neutral to slightly alkaline, with an optimal pH range typically between 6.5 and 7.5. This slightly alkaline environment allows the plant to efficiently take up the nutrients it needs.
Choosing the Right Fertilizer for Lavender
When selecting a fertilizer for lavender, options that are slow-release, organic, and have a low nitrogen content are suitable. Organic choices like compost, bone meal, or rock phosphate provide nutrients gradually. Bone meal specifically offers phosphorus to support root development and flower production, while rock phosphate is another natural source of phosphorus. Well-rotted compost can also supply a gentle, sustained release of various nutrients and improve soil structure.
If considering synthetic options, granular fertilizers with a low-nitrogen, higher-phosphorus, and potassium ratio are recommended. An NPK ratio such as 5-10-10 or 5-10-5 supports balanced growth without overemphasizing foliage. Avoid high-nitrogen organic fertilizers like blood meal on established lavender, as these can negate the desired effect of promoting flowers.
When and How to Fertilize Lavender
If fertilization is necessary, it should be done sparingly, typically once a year in early spring as new growth begins. This timing allows the plant to utilize nutrients for the upcoming growing season and flower production. Fertilizing after the main pruning can also be appropriate.
For granular fertilizers, lightly sprinkle the product around the plant’s drip line, avoiding direct contact with the stem, then gently work it into the top layer of soil. Afterward, water the area thoroughly to help nutrients dissolve and reach the root zone. If using a liquid fertilizer, dilute it to half or quarter strength and apply it directly to the soil around the plant. Avoid fertilizing in late summer or fall, as this can encourage tender new growth vulnerable to winter damage.
Troubleshooting Lavender Nutrient Issues
Lavender plants rarely show classic signs of nutrient deficiencies; symptoms are often subtle, such as yellowing of older leaves or stunted growth. If yellowing occurs, it is more commonly a result of overwatering or poor drainage than a lack of nutrients.
More frequently, problems arise from over-fertilization, which can manifest in several ways. Excessive leafy growth with few flowers is a common indicator, particularly if the fertilizer is high in nitrogen. Other signs include leggy stems, reduced fragrance, or leaves with burned tips. If over-fertilization is suspected, flushing the soil with plenty of water can help leach out excess nutrients. Withholding fertilizer for an extended period, sometimes for a year or more, is also advisable to allow the plant to recover.