Cacti make little demands on the water supply, but all the more on their plant substrate. Here’s how to mix your cactus soil yourself.
If you want the newly purchased cactus to grow properly, you should take a look at the substrate in which it is located. Often the succulents for sale are placed in cheap potting soil in which they cannot thrive properly. Good cactus soil is easy to mix yourself.
Cacti are generally considered to be undemanding and easy to care for, which is primarily since they rarely need to be watered. But precisely because cacti as succulents are naturally adapted to extreme locations, the right plant substrate is all the more crucial for a successful culture. Cacti can only grow well if, like all other plants, they can develop their root system well, which helps them to absorb the important nutrients from the soil.
Unfortunately, cacti are often enough simply put in normal potting soil instead of in cactus soil, which does not meet the requirements of most species. If it does not come from a specialist store, you should repot a freshly purchased cactus in a suitable substrate. Commercially available cactus soil, which is tailored to the needs of most cacti, is recommended as potting soil. However, if you want to cultivate, maintain or breed several different cacti in the house, it is advisable to mix the right soil for your cacti yourself.
Depending on the species, cacti have different demands on their substrate
Mineral or humus?
The plant family of the cacti (Cactaceae) comes from the American continent and is very extensive with up to 1,800 species. So it is only natural that not all members have the same location and substrate requirements. Cacti that come from the hot and dry desert and semi-desert areas or dry mountainous areas (e.g. Ariocarpus) prefer a purely mineral substrate, while cacti from the lowlands, tropical rainforests, and temperate latitudes have significantly more needs for water and nutrients.
The absolute starvation artists among the cactus plants include Ariocarpus and the partly epiphytic selenicereen, for example, the Aztec, Lophophora, Rebutia, and Obregonia species. They are best planted on a purely mineral substrate without any humus content. Echinopsis, Chamaecereus, Pilosocereus, and Selenicereus, for example, prefer a substrate with a higher nutrient and lower mineral content.
Barrel cacti come from South America and prefer loamy, slightly acidic soil
The ingredients of good cactus soil
Since many of our cacti come in rather small pots, an individual soil mix for each cactus is usually too time-consuming. It is therefore advisable to prepare a good universal mixture to which one or the other ingredient can be added if necessary for specialists. Good cactus soil should have excellent water storage properties, be permeable and loose, but structurally stable, and have good ventilation.
The individual components are usually potting soil, potting soil or very well-seasoned compost (three to four years), quartz sand, peat or coconut fiber, coarse-crumbly dry loam or clay, pumice and lava fragments, or expanded clay fragments. These components can be used to mix different humus-mineral substrates that most cacti can tolerate. The drier and more sandy the natural location of the cactus variety, the higher the mineral content should be. The demands on the pH value and lime content of the soil vary depending on the type of cactus. The pH value of the self-mixed cactus soil can be easily checked with a test strip.
Mix the cactus soil yourself
For a simple universal cactus soil mix, 50 percent potting soil or potting soil with 20 percent quartz sand, 15 percent pumice, and 15 percent expanded clay or lava fragments. The mixture of 40 percent humus, 30 percent loam or clay, and 30 percent coconut fiber or peat is a little more individual. Then add a handful of quartz sand per liter to this mixture. It is important that the coconut fibers are soaked in water before processing and then processed slightly damp (but not wet!).
Clay and loam should not be too crumbly, otherwise, the cactus soil will be too compact. Under no circumstances should you use play sand or construction sand for the sand, as this will compact a lot. Now mix the ingredients well in a flat box or on a cardboard box, let everything sink for a few hours, and mix the soil again. Tip: Many cacti prefer a low pH. You can achieve this, for example, by using rhododendron soil instead of humus. If you have used potting soil instead of potting soil to mix your cactus soil, you should refrain from fertilizing the cactus in the first year, as this soil is already pre-fertilized.
Purely mineral cactus soil consists of a mixture of 30 percent crumbly loam and fine-grained lava fragments, expanded clay fragments, and pumice in equal parts. The grain sizes of the individual components should be around four to six millimeters so that the fine roots of the cacti find support. Since this mixture does not contain any nutrients, cacti in a purely mineral substrate must be lightly fertilized on a regular basis.