Succulents have become hugely popular in recent years, but giving them the right compost is crucial if they are to grow and thrive. Even the compost that you buy them in may not be suitable so it pays to investigate and if necessary repot them into some which will suit their needs.
Left in the wrong compost it can be virtually impossible to regulate the amount of water that the plants receive. You may then find that roots and stems rot, and the whole plant may die. Some nursery growers raise plants in peat or peat-free composts which contain high levels of organic matter and while this may be OK initially, as the organic matter starts to decompose, the structure of the compost deteriorates and the health of the plants growing in it suffers.
Why are succulent plants different
Originating from dry, arid landscapes succulents have evolved to conserve moisture in their tissues. Water can be stored in fleshy roots, stems and leaves for use at times of low rainfall and drought. Cacti are also a specialised form of succulent plant. Such plants also limit the amount of water that is lost from the surface of the stems and any leaves. In may cases they protect themselves from being browsed for moisture by animals through having thorns or toxin sap.
Soil conditions where these plants grow in their native environments are generally stony or sandy, with little in the way of organic matter. This means that the plants have evolved in very open, well aerated mineral soil which is also very freely drained. In such conditions waterlogged is unlikely, and if it does occur will last only a short time during which the plants are able to stock up on the moisture they need.
Growing all succulent plants in cultivation – both outdoors (where appropriate) and as houseplants indoors – needs to take account of their natural adaptations to a water-sparse environment. Providing them with an appropriate soil or compost is the best way to succeed in growing them.
Can you use multi-purpose compost for succulents
To be frank, creating a truly ‘multi-purpose’ compost is impossible. And for the optimum results with the vast range of different plants which gardeners grow, soils and composts should be tailored to suit their specific needs.
Multi-purpose composts are all based on forms of organic material, either in the form of peat or a peat-alternative. This organic material acts like a sponge in the compost, holding onto water and nutrients for the plants to use. And, when fresh, this spongey nature also helps to hold the compost open to allow drainage, prevent it becoming waterlogged, and let air permeate to the plant roots which is essential for their growth.
But as I’ve already mentioned, this organic matter will break down by decomposition over time so that the open structure deteriorates. This reduces aeration and impedes drainage. Not the conditions which the roots of succulents have evolved to thrive in. This means that multi-purpose composts are not suitable for succulent plants.
Which composts suit succulent plants
Sandy, gritty composts are best for growing succulents and cacti. These can be purchased as specialist mixtures or made up from different ingredients. The best base for a succulent compost is a good quality loam (the best type of soil). This will have a high mineral content that won’t decompose or break down. In turn that means that it will tend to retain its structure. The loam will also contain a small amount of organic matter.
This is then mixed with the drainage ingredients to make it more suitable for succulents. Such ingredients take the form of ‘sharp’, angular sand and fine horticultural-grade grit. The particles of both will help to hold the compost open and maintain drainage and aeration to prevent water-logging around the roots of the succulents.
I make my own succulent compost by mixing 1-part loam by volume, with 1-part sharp sand and 1-part fine horticultural grit. I use a flower pot to measure out the quantities, then mix the ingredients throughly. For plants which have been previously grown in peat or peat-alternative composts, I tease lots of it from the roots before repotting in my gritty mixture. And where possible I use unglazed terracotta pots.
This makes it far easier to regulate the moisture in the compost to suit the succulents. Excess water can be left to drain away to keep the roots alive and healthy. All in all a much better and more natural environment for such plants to grow in than a multi-purpose mix.