Lavenders do not need additional feeding or fertilizing as they’re adapted to living in sandy, relatively low fertility soils in the Mediterranean region of Europe. Adding fertilizer will cause the lavender to produce fewer flowers, less fragrance, and grow a leggy, untidy appearance.
Lavenders will produce the most oil, fragrance, and flowers and look their best in nutrient poor, sandy soils that replicate their natural environment.
Adding fertilizer is contrary to lavender’s preferred lower to medium fertility conditions and will result in an unhealthy plant that may turn yellow or droop in appearance.
Why You Shouldn’t Add Fertilizer to Lavenders
Lavenders are native to the Mediterranean region of Southern Europe and thrive in dry, consistently sunny areas of Southern France, Italy, and Spain.
They prefer to live in rocky or sandy soils that are slightly alkaline, although they will tolerate mild acidity. (Lavenders will grow in soils between pH 6.5 and pH 7.5)
Sand and gravel have little to no nutrient value, but provide the ideal soil structure for lavenders. Lavenders require well-draining soils that do not hold onto water. The sandy open porous texture also allows for the roots to establish properly as lavenders will struggle to grow in compacted soils.
Lavenders will attain all the nutrients they need from organic material that is in the soil, with around 30% sand and 70% compost providing the right balance of drainage and a modest amount of nutrients when amending the soil for lavender planting. (For more details on amending soil, take a look at my guide to transplanting lavenders).
If you add nitrogen-based fertilizer to lavenders, then the foliage of the plant will turn yellow and result in a leggy untidy appearance. (If this has happened to your lavender read my guide on what to do). In some cases, the nitrogen can burn the lavender’s roots and kill the plant altogether.
Lavenders thrive on a ‘less is more’ approach to care when it comes to fertilizer and watering. As long as you get the conditions right then lavender growing can be very low maintenance.
Adhering to the correct watering practices and positioning your lavender in the sunniest spot in your garden (ideally more the 6 hours of sun per day) will have far more of a positive influence on the quality of lavender blooms and the intensity of the fragrance than the fertility of the soil.
Successful lavender growing is more about replicating conditions of the lavender’s Mediterranean home, so low to medium fertility soil without additional fertilizer will yield better results.
Balancing Fertile Soils for Lavenders
Garden soils that are rich in organic matter or clay tend to be too high in nutrients and retain too much water to get the best out of your lavenders.
An excess of nutrients in the soil will promote foliage growth at the expense of flowers which is contrary to the goal of lavender growing.
If you have already added fertilizer or have naturally rich soil then you can amend the soil with sand or gravel which will counteract the higher fertility.
Mix in sand or gravel into the soil to a depth of 18 inches and a width of 12 inches as this will accommodate the root system of a lavender plant at full maturity.
Try to aim for a 30% sand to 70% compost mix to ensure the ideal soil structure and level of fertility in the soil.
If you have clay soil it is always better to amend it with gravel rather than sand to ensure the soil remains suitable porous, so that the roots can establish. (Read my article Growing Lavender in Clay Soils for more information).
If amending the soil is problematic then you can alternatively transfer the lavenders into pots.
Lavenders grow exceptionally well in pots as they can provide ideal drainage conditions and you can add your compost/sand mixture more accurately without the labor-intensive task of digging down into the soil.
Potted lavenders can also be brought indoors to be protected from winter frost if it is not a cold hardy species (English lavenders will survive cold winters, whereas Spanish, Italian, and French lavenders need mild winters and cannot tolerate frosts).
Too much sand or gravel is far better than not enough as they’re highly important for maintaining good drainage and balancing fertile soils. Overly fertile or water-logged soils will kill lavender whereas they will thrive in under fertilized, well-draining soils.
Should I Apply Mulch to Lavenders?
Applying mulch can be a good way to add some nutrients to the soil as the material can break down slowly and release nutrients over time rather than a fast-acting liquid fertilizer which would overwhelm the lavender’s roots.
However, you will have to be careful for two reasons:
- Applying too much mulch composed of organic material (such as compost, leaf mold, or manure) could increase the likelihood of lavender plants developing the fungal disease root rot. Lavender roots need to be able to dry out in between periods of watering to stay healthy. Organic material can hold onto and store water for prolonged periods. If the lavender roots are exposed to this consistent moisture then this will significantly increase their susceptibility to developing root rot.
- Mulch such as manure has a high nitrogen content which promotes foliage growth at the expense of flowers and the plant will develop a drooping appearance or yellowing foliage. Manure can also be fairly acidic whereas lavenders prefer alkaline soils.
A balance between organic material and sand or grit is necessary for growing lavenders to provide some nutrients but also provide the structure and lower to medium fertility conditions that lavenders need to produce blooms.
The best way to strike this balance is to amend the lavender’s soil before planting with around 70% well-rotted compost and 30% sand. If your lavender is already planted then you can ease the plant out the ground with a fork and amend the soil before replanting.
(Read my article, on the best soil mix for lavenders in pots and containers).
A mulch of wood chips or bark can help suppress weeds, maintain a good soil structure, and add some nutrients as they break down into the soil.
A good alternative and organic mulch for lavenders is to use a layer of white stone (preferably limestone) around the planting area.
Commercial lavender growers distribute white colored stone around their lavenders to reflect light back onto the plant which will increase blooms and oil production. Limestone has the added benefit of maintaining the alkalinity of the soil to counteract acidic soils which would otherwise harm lavenders.
Key Takeaways
- Lavenders do not need additional fertilizer because excessive nitrogen will cause the lavender to turn yellow, produce fewer flowers, and grow a leggy appearance.
- Lavenders are adapted to the low to medium fertility sandy soil conditions of the Mediterranean region in Europe.
- Lavenders produce the best blooms when gardeners recreate the poor soil conditions of their native habitat.
- Adding sand and gravel to the soil before planting lavenders will help to counteract rich fertile soils so that they are more suitable for growing lavender.
- Wood bark or limestone are the best mulch materials. Wood bark suppresses weeds and adds some natural fertility to the ground over time. Limestone will reflect sunlight back onto the lavender which will help promote flowers and fragrance, as well as maintain the optimal soil pH.