If lavender is planted directly into clay soil, it won’t thrive. However, you can grow lavender on clay soils if you significantly amend the soil beforehand with gravel to significantly enhance the drainage and soil structure. Clay soil absorbs too much water, which will cause the disease of root rot.
From the following angles, clay soils can be troublesome for lavender cultivation:
- The nutrients in clay soils are abundant. On the Mediterranean region of Europe, lavenders are specifically adapted to growing in poor quality, low nutrient, sandy soils. High fertility soils encourage the growth of leaves rather than flowers, giving lavender a lanky and messy appearance.
- Since clay soils are so prone to compaction and can bake to a crisp under prolonged sunlight, lavender roots cannot grow there.
- Lavenders can tolerate mild acidity (pH 6.5) but prefer alkaline soils up to pH 7.5. Clay soils tend to be acidic.
If your soils are clay, you still have a few viable options for growing lavender. What you can do is:
- Add aggregate (grit or gravel) to the clay soil to increase texture and maintain the proper amount of fertility.
- Use improved soil and raise the beds.
- Lavender can be grown in containers.
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How to Amend Clay Soils for Lavender Growing
Sand is less able to maintain a porous, well-draining soil structure in clay soils because it is too fine since clay soils are prone to compaction. I have personally seen a garden where sand had been added to heavy clay, and over time the soil had grown thick and nearly cement-like in texture.
In clay soils, however, gravel performs significantly better in terms of long-term structural integrity preservation. The huge particles interlock in such a way that more air pockets are left in the soil, which is perfect for amending clay and allows water to effectively enter and roots to form in the soil.
The more space you modify around the lavender, the better if your garden is constructed of especially hard clay and drains noticeably slowly.
Otherwise, water might gather where the clay meets the amended soil. Always plant your lavender at a higher region of your garden rather than a lower one, as the higher area will naturally have better drainage. The lower area will normally have slower drainage.
The best advice is to steer clear of digging or working in heavy clay soil when it is wet since it will be highly slick and stick to your boots and shovel instead of allowing for clean digging. This can be quite annoying!
1. To amend the soil, dig out a section of clay that is 18 inches wide and 12 inches deep. This will fit all kinds of lavender when they are fully mature.
2. Get rid of the heavy clay soil or repurpose it in other parts of the garden.
3. Use a mixture of gravel and garden compost (or soil mix) that is roughly 30% gravel to 70% compost to replace the clay.
4. Ensure that the soil in the adjusted area is evenly mixed with the compost and gravel. While a spade can be used, I like to use a trowel to make sure that each component is dispersed uniformly.
5. Fill the hole with sand and compost after planting the lavender. Do not step in with your heel as this would compact the dirt and make it harder for the roots to take root. Instead, firmly place the lavender in the hole with your hands to give it some stability.
6. Soak the lavender for a while; this will assist to lessen transplant shock.
See my article How to Transplant Lavender for more details on planting, caring for, and watering new lavender plants.
Should I add Mulch to Lavender in Clay soils?
In clay soils, mulch made of wood bark, white gravel, or limestone is ideal for lavender plants. While gravel or wood bark allow water to run through the soil and prevent weed growth, organic debris like compost or leaf mold may retain too much water and may cause root rot.
The fact that white gravel or limestone effectively reflects light back onto the leaves for more sunshine and heat around the plant, so producing a microclimate, is an added benefit. I picked up this advice for boosting the output of lavender oil and scent from commercial lavender producers in California.
If you have inherently acidic soils, limestone will eventually add to the soil’s alkalinity, which is a smart strategy to maintain the proper soil pH for lavender (pH 6.5- pH 7.5).
You can also choose to grow lavender in raised beds or pots if the climate is unfavorable. Lavender also requires full sun, low to medium fertility, adequate drainage, and occasional watering. Clay soil might make it difficult to meet these requirements, but raised beds and pots make it extremely simple.
Alternatives for Lavender Growing in Clay Gardens
Create a raised bed for your lavender plants or grow them in containers to prevent the issues caused by clay soil.
These two choices are ideal for cultivating lavender because:
- Raised beds and pots are excellent ways to lift lavender plants out of soggy soils and enhance drainage.
- Without having to dig out and remove a lot of clay, you can precisely apply the proper amounts of sand/gravel (30%) and compost (70%) to imitate the Mediterranean conditions that lavender prefers (in terms of soil fertility and drainage).
- Before winter, pots can be brought indoors to avoid damage from frost. (Lavender species from France, Spain, Italy, and any other language outside English are not frost tolerant. Only the English cultivars can withstand cold and frost.
For all the information you need on taking care of potted lavenders, check visit my article How to Grow Lavenders in Pots.
Raised beds can still be a cheap and efficient way to grow plants in dense clay soils, but growing lavender in pots is easier and needs substantially less work than making a raised bed.
Check out this video for the simplest and most affordable instructions on building raised beds:
Key Takeaways:
- Clay soils hold too much moisture for the growth of lavender. Lavenders like soil that drains properly and doesn’t retain rainwater.
- To provide the beneficial drainage and low to medium fertility conditions that lavenders demand, you must dig a hole that is 18 inches wide and 12 inches deep, then fill it with a mixture of 70% compost and 30% gravel before planting the lavender.
- When amending clay soils, never use sand; use gravel or grit instead for improved soil structure.
- Clay will be sticky and stick to your spade if you dig it in rainy weather. Always wait for a day that is dryer.
- A less time-consuming option that offers better growing conditions for lavender than preparing and modifying clay soils is planting lavender in containers.