You perhaps received a small lavender plant as a gift or you just bought one yourself looking forward to enjoying its blooms and its great smell? Yes, but it needs a larger home and, even more importantly, way more soil. What soil should you use?
Lavender is a Mediterranean shrub that needs dry, organic poor, and aerated soil. Normal potting soil is not suitable for lavender because it is too compact and water-retaining. A slightly alkaline growing medium obtained as a mix of potting soil, perlite with clay pebble is ideal.
We know now that potting soil, as it is, it is not the best for your lavender. Why and what should you do? Understanding how lavender grows is the very first and most important step to let you then decide which soil to use.
Lavender is a shrub that thrives in the Mediterranean regions. If you’ve ever been in Italy or France, especially during the hot summer, near a coastal area, or during some hiking, it is not uncommon to find herbs such as rosemary and shrubs like lavender growing in the wild.
Lavender grows in the wild among rock cracks, dry soil, under intense heat, and little water. The best way to promote their growth is to emulate such conditions even if you decide to plant in a pot or your garden.
The soil conditions in which lavender thrive are airy and well-drained soil, neutral to alkaline and nutrient-poor.
The ideal soil for lavender to thrive is a rocky-like soil with lots of air, grit-like material like perlite, clay pebbles giving great draining properties to the soil.
This is related to where the lavender grows in the wild. It grows in an area with little rain and is very hot. For this reason, it develops a root system that, by nature, tries to extract all the water around to survive. However, in a humid climate or under human control (the gardener watering them) they will definitely develop root rot if placed in a normal potting mix.
The ideal pH for lavender is anything between 6.5 and 8. This means that lavender thrives in neutral to slightly alkaline soil.
Lavender will suffer in the case of acidic soil with a pH lower than 6.5. To know the pH of your soil you can perform a soil test, it can be quite cheap and fun to do.
The reason why lavender is negatively affected by acidic soil is again related to the conditions in which it grows. Nutrient-rich soil tends, over time, to become slightly acidic due to the broken down mechanism of the organic material in it;
Lavender as many wood type herbs and shrubs perform better in poor soil. That’s why it is not recommended to fertilize lavender and neither uses compost on the mix if not in a very limited amount.
Of course, any liquid fertilizer (those are very fast-acting) is not to go for lavender soil if you do not want to see it suffer.
This should make clear why regular potting soil is not an option for lavender. Indeed, such soil is too water retaining and too nutrient-rich.
The best lavender potting soil is obtained from a mix of:
- One-third of perlite (or pumice): as discussed in this article, perlite is the very light rock of volcanic origin mainly porous that is very well known to increase drainage;
- One-third of potting soil: this is to give to the growing medium so obtained some structure that can hold water and have a few nutrients;
- One-third of clay stones or oyster shell: this is an ever rough structure that allows, mixed with the perlite, to create large air space within the growing medium allowing airflow and more importantly, preventing wet feet and waterlogging.
These are the products I normally use or recommend
This is my favorite mix and the one that allows my lavender to grow quite well on planters around you can find perhaps other recipes. Gardening is not an exact science so other combinations might work. However, remember, keep the soil light and with lots of coarse material for breathing
To avoid getting messy while preparing the soil I do recommend going outside or on a working bench table. If you have one or several pots, place an equal amount of scoops of each ingredient in each pot.
Tip: you do not want to just drop the perlite at the top of the growing medium. You need to mix it within it. This is because perlite has the tendency to float in water and, if you do not make sure that the mix is uniform, you will end up with the perlite floating on the surface of the pot. This makes teh perlite useless and annoying (as it flies away when dry).
After all the ingredients are on the planter start mixing them vigorously with a trowel or even better with your hands (wearing adequate garden gloves, if yours are old check this out on Amazon). You want the three components to be uniformly mixed, this is quite important.
If you have your lavender indoor, you are settled. However, if you grow lavender outdoors, I would also add a soil cover made of gravel or/and oyster shell (below a good brand that you can find on Amazon).
What about cacti soil? Can you use cacti soil for lavender?
Lavender can successfully be grown in cacti soil. However, this is likely to require more watering than the lavender mix. Remember, lavender is not a cactus and does require more water than a cactus. I water my succulents once a month while my indoor lavender once a week.
The finger test
Once you’re done you should be able to stick your finger and “taste” the structure of the mix so obtained. Does your finger feel pressed? If so, something is wrong with the mixture. If you can dig your finger with ease (and some scratches from the grit part, be careful) then you did a good job.
The same requirements in terms of soil drainage and aeration do apply also for lavender planted directly into the soil of your garden. However, here I need you to add some extra care as you do not have total control of the soil here as you have on a planter.
First, you need to understand if your soil is good enough for lavender. What I normally do, as suggested also by more experienced gardeners, is the water retention test. Hence, dig a hole, roughly the same size as the one needed to plant your lavender and fill it with water. Then observe.
Is the water going through quickly (like is gone in 10 seconds or less) or tend to create a paddle that stays there for 10 minutes or more? In the second case, you might want to prepare the garden soil so to be suitable for lavender.
In this case, you have to options:
- Create a raised bed: this is no more than a giant pot. Hence, when building it you can go ahead with the growing medium mix discussed earlier;
- Amend the soil: in this case, you need to modify the soil of your garden to be more suitable for lavender;
The best soil amendments for lavender are perlite, clay stones, and any light, not water absorbing gritty material that increases drainage and airflow in the growing medium.
What I normally do to amend the soil in case I decided to plant it outdoor is:
- Dig: Create a deep hole in the area I want to plant lavender. If you want to plant multiple of them then go with a trench. I would suggest at least 20 inches deep and 20 inches wide if you have space. In general depth, the higher the better.
- Bottom Cover: Place at the bottom of the hole a few layers of gravel /pebbles/clay stones. Despite being this a massive mistake in potted plants, it is good practice when outside as will prevent the roots from getting wet as the eventual excess water will fill the rock’s spaces rather than developing the roots.
- Prepare the Mix: Prepare the mix to fill the holes. The recipe is the same as before and here reported again. If you do not have perlite you can replace all the volume with clay stones. If you have lots of soil to cover you can also use some soil cover as this is cheaper usually the potting soil
- ⅓ of potting soil: this can be replaced with topsoil as this one on Amazon
- ⅓ of perlite
- ⅓ of clay stones
- Drop half of the mixture in the hole;
- Place the lavender: be careful not to break too many roots and the remaining half of the mixture to cover the spaces between teh plant and the hole.
- Soil cover: Apply a soil cover of gravel or pebbles to avoid weed from taking and competing with the lavender plant
Now just pat yourself on the shoulder and wait for your lavender to grow and bloom.
Growing lavender is not particularly difficult if you do not live in a very cold or wet place. It is a stubborn plant. For those of you struggling with lavender, I would suggest going for the easiest type such as Grosso and Spanish.
However, if you are having trouble, probably there is something wrong with the soil. Here I noticed chatting with some friends over the topic. Chances are that you fall into one of the following.
Clay soil is quite inadequate to grow lavender. Indeed, the lack of airflow, poor drainage, and its ability to retain more nutrients, are all features that will negatively affect the growth of lavender plants.
My friend David planted its poor lavender plants in pots using its garden soil that was very high in clay content. There are several reasons to avoid gardening soil for potted plants (such as the presence of pests or other insects in it) and, on top of that, most of the time this is unsuitable for lavender.
Compost is high moisture retaining growing medium that is not advised, if not in small amounts, to be used for lavender soil. The only case in which compost can be added in a growing medium designed for lavender is in a very dry area. In this case, you should not go over 10%.
This is because the water-retaining ability of compost is not ideal for lavender. The compost tends to breakdown over time leading to increased acidity. This is another condition that is not very tolerated by lavender.
This is a problem that negatively affects not only lavender but the majority of shrubs and culinary herbs.
Sand or perlite should never be added to clay soil. This is because sand does not provide drainage or aeration to clay soil but, rather the opposite. Indeed, the small air pockets between sand granules are filled with the smaller clay particle forming an even denser structure than the original clay.
Sand and perlite can be beneficial in clay only and only if in large amounts (at least 50% of the mix). Moreover, perlite might not even be that good either as, over time, it tends to be pushed up (it floats in water) by the clay until it floats on the top. At this point, the perlite will not sink again (lighter than water) if not by external action.
Reading some gardeners forum I came across a guy that, in an attempt to avoid the soil amendment (he was planting lavender outdoors), decided to skip the digging process and add sand to its clay garden soil (rather than creating a mix for it). After a month his lavender started wilting and dying. This is normal and also discussed in other sources.
This is often a problem when planting lavender outdoors or in a large planter. Lavender hates wet feet. If you plant your lavender you might not pay attention and leave less soil around the plant “crown” (the wooden part where all the branches depart) creating a little basin where the water accumulates or stagnate more. You want to avoid this.
A strategy is to put a bit extra soil around teh plant so to create a “volcano” that then you cover with the soil cover (so the soil does not fly away over time). This will allow the water to gently flow over and far from the plant base limiting the amount of water your lavender takes. This is particularly important if it is placed outside in rainy weather.
Despite not being a common problem as the others, the soil pH can be too low (below 6.5 or acidic). In this case, to be 100% sure go for a soil test (they are cheap and quick). If the test comes out positive, then you need to add lime for instance so to increase the pH to at least 6.5, ideally 7.
Lime can be easily found in gardening shops or even online (as this one on Amazon). Lavender can grow well in slightly alkaline soil.
Can I Use Multipurpose Compost For Lavender?
Multi-Purpose compost should not be used for lavender due to its water-retaining capability, nutritional values.
One sentence per bullet point below. Each sentence summarises a key point of the article. From 3 to 5 bullet points
- A good lavender soil is the one that emulates the natural conditions in which lavender grows
- Drainage is key
- The lavender ideal growing mix should be airy, gritty, and slightly alkaline. Compost and a large volume of potting mix are to avoid.
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