Most succulents, whether planted indoors or out, require a different type of soil than other plants. With their thick, fleshy leaves, succulents can store water and even nutrients in dry climates. They can endure extended periods of drought and tend not to like too much humidity. By using a soil made specifically for succulent-type plants — which mimics their native soil conditions —growers can keep the leaves and roots healthy and thriving.
Many species of succulents prefer warm temperatures, whether grown indoors or outdoors. Since water is stored in the leaves, care must be taken to avoid freezing conditions; water expands when it freezes, so the moisture held in the succulent leaves will burst the plant fibers, resulting in mushy plants that could die.
Like any plant, succulents need the right amounts of sunshine and water. This is where using a well-draining succulent soil comes in handy, as it allows for proper drainage.
A basic potting soil common at plant nurseries usually contains peat moss as its primary ingredient, but this tends to repel water, preventing it from properly saturating the roots. On the other hand, some potting soils contain materials that hold water very well — a little too well for most succulents. A good idea to follow is to re-pot the plant using succulent soil to free up any bound roots and to allow for optimal airflow.
Succulent soils are made up of organic and mineral components. Organic materials add nutrients to the soil and work to retain just the right amount of moisture. The mixture might include compost, tree bark, and coconut coir. The mineral components are usually some combination of sand, gravel, grit, and perlite. Avoid soils with clay or vermiculite, as these minerals hold more water than is necessary.
The specifical mineral makeup of succulent soil affects the grit size, which in turn affects its texture and porosity. Sand is the mineral additive with the largest diameter. Silt falls somewhere in between, and clay has the smallest diameter, which is why it compacts so firmly and is not suitable for succulents. Generally, sandy soils work very well for succulents — the large particles, and therefore larger pores, mean they dry out quickly.
Growers can undertake two home tests to estimate their soil's texture. Simple feel tests involve feeling the sand particles in the soil and estimating the silt and clay content based on how flexible and sticky the sample feels — for example, whether it holds together after being squeeze in a fist.
Jar tests also determine the amounts of sand, silt, and clay and allow the grower to make any adjustments to the combination to improve plant health. To run a jar test, fill a mason jar 1/3 full of soil, then add water to about one inch from the top. Add a tablespoon of powdered dishwashing detergent, screw on the cap, and shake the mixture.
After one minute, mark the top of the soil division on the side of the jar. Mark again after two hours, and again after 48. A soil texture analysis worksheet will help you understand the results.
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As a rule, the average potting soil is not ideal for succulents, but that doesn't mean you need a whole new bag of soil. By adding mineral grit like sand at a ratio of 1:1 or 1:2, you can transform a basic soil — containing bark, peat moss, and compost — into an adequate succulent soil. Just be sure that your initial soil has no moisture-retaining crystals.
Since each succulent requires slightly different care, many gardeners find that a more customized soil blend recipe works well. Create a well-balanced soil from one part organic material — potting soil, pine bark, compost, or coconut coir — to two parts coarse sand, perlite, pumice, or fine gravel. Combine the options in each section however you choose, ensuring you end up with 1 part organic to 2 parts mineral. Coarse sand such as builders sand is ideal for the mineral component. Avoid beach sand, as the salt content will harm the plants.
Although not necessary, top dressings on the surface of the soil can help protect the leaves from standing water and minimize rot. They can also enhance and polish the look of the potted plants. Common materials for top dressings are pebbles, sea glass, colored sands, and moss.
Succulents planted in outdoor areas tend to get more sunlight and airflow than indoor plants, which helps them dry out, even if the soil is a bit more moisture-retentive. When necessary, outdoor soil can also be enhanced for succulents by placing them in a gritty, sandy loam and topping that with a layer of gravel mulch. Raising the soil level or planting in beds is also an option, especially if the garden soil contains a high amount of clay.
To avoid overwatering succulent soil, it's helpful to keep a record of the watering schedule. Allow the soil to completely dry out before thoroughly soaking the growing medium. In addition to a soil that is porous enough to let the water pass rather than holding onto it, drainage holes are essential when you're watering plants in this way. They will ensure the roots do not soak in the water at the bottom of the pot.
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