How to Prepare Soil for Outdoor Succulent Gardens
Are you thinking of adding more drought tolerant plants like succulents, to your garden?
Plants that love arid conditions are an easy way for gardeners to keep their thumbs green without having to invest a lot of time or effort.
Just give them the conditions they need, and they’re generally quite self-sufficient after that.
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Planting succulents is also a smart way to incorporate water-wise practices and expand your garden into areas outside of established irrigation zones, like rocky slopes or sandy areas where other flora won’t thrive.
But for xeric plants to thrive in dry conditions, they need a different type of soil than regular garden loam, which is typically too nutritious and retains too much water for too long.
The answer to this is to create your own medium that’s not overly rich with a gravelly or sandy texture for sharp drainage.
This can be used in beds and borders as well as in large planters, and it’s easy to make your own signature batch with locally sourced ingredients.
Plus, this recipe is also a smart choice for any drought-tolerant plants that prefer lean, well-draining soil.
North American natives like gaura and liatris flourish in it as do Mediterranean herbs such as rosemary and thyme, and alpine plants like anemones.
So, are you ready to whip up your own water-wise growing medium? Then let’s dig into how to make succulent soil for outdoor gardens!
Succulent Plants and Water
To cultivate any plant successfully, it helps to replicate their natural environment.
Most wild succulents grow in gravelly or sandy soil, and often thrive in small pockets of lean dirt on cliff sides and in rock crevices.
A feature of succulent plants is that they store water in the thick, fleshy tissue of their leaves and stems. Popular types include cacti, echeveria, and sedums.
They also take many shapes and sizes, from low-growing ground covers like English stonecrop to midsized agaves and aloes or towering organ pipe cactus.
Most occur abundantly in semi-arid zones that receive regular rainfall, even if it is brief or infrequent. And when the rains do come, the gritty soil becomes fully saturated but dries out quickly.
To survive and get the most out of these rare dousings, the roots of these fleshy plants have adapted for rapid rehydration.
The roots are shallow and spread out in a diffuse net around the plant to catch as much of the water as possible. And they’re highly sensitive to water in the ground, absorbing as much as 50 percent of available moisture during heavy rains.
Some varieties do have a large taproot, but they’re more for anchorage than for finding groundwater at depth.
Other adaptations help succulents to conserve water as well, such as a thick and waxy surface cuticle layer to protect the water-storing tissues, as well as hairs and spines to protect and insulate against harsh elements.
But the key to their good health is in the soil – it must be well-draining to keep the delicate roots happy and prevent root rot.
So let’s get into the components for soil that succulents love!
Ingredients for Well-Draining Soil
All soils are made up of five basic ingredients in varying degrees:
1. Minerals come from the erosion of rocks and are divided into three classes: clay, silt, and sand. The percentage of particles in the three classes is referred to as texture – clay particles are small, silts are medium, and sand particles are large.
2. Organic matter comes from the residue of animals, microbes, and plants as they live, consume, and eliminate, then die and decompose. The amount of organic matter determines its quality for agricultural purposes.
3. Living organisms such as plants, micro-organisms like bacteria and fungi, as well as animals, birds, insects, and even humans all contribute to the cycle of soil building.
4. The primary gases of nitrogen, carbon dioxide, and oxygen are found in the small spaces between mineral and organic particles.
5. Water is the final ingredient and the amount of moisture in the soil determines in good part how much a plant can grow.
The size of organic and mineral particles impact the rate of water infiltration, with large pore spacing at the surface providing the fastest rate of infiltration.
In a nutshell, coarse and gritty growing mediums provide the porous nature for aerated roots, optimal moisture saturation, and the fast drainage needed for succulents to thrive.
And because they do best in growing mediums that aren’t overly rich, they require only a little organic matter.
The Recipe
To create optimal conditions for your succulents, the site must be well-draining and filled with gritty or sandy earth.
If you don’t have perfect soil in your beds and borders, you can use a commercial cactus potting mix, but this can get pricey if you’re amending large areas.
I’ve also found that commercial cactus mixes, especially ones that contain peat moss, are still too slow to hydrate and drain for my liking.
Adding grit to commercial mixes gives faster infiltration and sharper drainage, but it’s just as easy, and more economical, to make your own.
As a general rule of thumb, make a batch consisting of one-quarter of organic materials for nutrition and tilth to three-quarters of minerals for aeration and drainage, or one part organic to three parts mineral.
For indoor containers, I use an extra part of organic material – you can find how to make potting soil for succulents here.
But for outdoor garden beds, a lean medium works best.
For the organic matter, I recommend materials such as fine bark mulch, coconut coir, compost, garden loam, or worm castings.
Avoid materials like peat moss which is slow to rehydrate and makes it difficult to quickly drench the roots.
Good mineral options for drainage and a porous, lofty texture include aquarium or bonsai pebbles, chicken grit, crusher dust, granite or shale chips, lava pearls, pea gravel, coarse perlite, pumice chunks, and landscape sand.
With the mineral portion, it’s helpful to choose two textures with different sized particles, such as pumice and sand – combined, they provide better aeration and drainage than a single texture.
Avoid compacting minerals like fine sand or those that retain water, such as non-calcined clay and vermiculite.
Prepping Garden Beds
Premix your ingredients on a tarp or in a wheelbarrow or dump them all on site and mix in place.
Prepare the dirt in your xeric garden beds to a minimum depth of six inches and up to 24 inches, depending on the varieties grown.
Small varieties like echeveria and lithops are fine with a shallow bed but ones with deep, anchoring tap roots like yuccas need greater depth.
To provide even better drainage, mounded berms or raised beds are also helpful.
Beds can also be cut into a slope or located in naturally occurring cracks and crevasses in the terrain for a sloping topography, letting gravity take care of some of the drainage.
Containers and Planters
Prepare the same recipe for outdoor containers, planters, and troughs, adding in an extra half to one part of organic material if desired.
The earth in containers dries out and is depleted of nutrients faster than in garden beds, and I find a little extra compost keeps container plants lush with strong growth.
Also, to accommodate their delicate roots, choose shallow containers with drainage holes for your succulents.
Pots and planters that are too deep, or those without drainage holes, tend to keep the deeper layers saturated for too long.
Fast Saturation, Sharp Drainage
Keeping your outdoor succulents healthy and happy starts with giving them the growing medium they need for fast saturation and acute drainage.
Just follow the proportions of one part organic matter to three parts mineral content to give your plants the nutrients they need plus a porous, non-compacting soil with good aeration and a sharp texture for fast water movement.
And remember, this blend makes a good choice for any plants in your water-wise garden!
What kind of soil do you like to use for plants that love dry conditions? Tell us about it in the comments section below.
And for more succulent care and cultivation ideas, add these guides to your reading list next: