Marl as a substrate for cacti: is it really so good? How to use it and with which plants does it work

The use of marl as a substrate component for the cacti’s cultivation has been widespread for years, especially in Italy. Thanks to the studies and research conducted by my friend Andrea Cattabriga – grower, researcher and succulent expert at the international level. But what are we talking about, when we discuss marl? Quite simply, a greyish and highly friable rock, to the point of breaking up into flakes until it becomes powder. It’s used to create substrates for the cultivation of many cacti and some succulent plants when combined in some dosages with other materials such as quartzite, pumice, sand, gravel, lapilli, peat, field soil (clay).

In this article we explore the benefits of using marl in cactus cultivation, we see how to make a valid marl-based substrate, and we try to understand, above all, with which kinds of cacti this material can work and with which ones it should be avoided. (…)

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Substrate, loam, soil mix: which is the best soil for cactus and succulent plants?

I may look like a mordant, but I want to clear the field of misunderstandings and false myths: the right soil for cacti does not exist. There are many types of soil (or composts, substrates, mixtures, the question does not change) and there are genera that prefer certain substances and others that require more. Established this and removed one of the first Faq (Frequently Asked Questions) by cacti enthusiasts to the first arms – “Which is the best soil for my cactus?” – it can be said on the contrary that on the one hand there are the characteristics that a good soil for cactus must necessarily have; on the other hand the needs of the single plants. The question was simple and the related answer was given by italian cacti expert Giuseppe Lodi, who, after observing “the butts of roots of certain imports” and having noticed how these were encrusted with clay loam, suggested a base soil absolutely natural and versatile: “You can start from a mixture of common clay loam (field or garden), coarse sand and leaf soil, in equal parts. Of these three components none of them can be enough, alone” (Giuseppe Lodi, “Le mie piante grasse” – Edagricole).

Except perhaps for the difficult availability of the loam of leaves (be careful to go for the woods and get bags of decomposed foliage: there are fines for collections of this kind), the recipe provided by the Italian pioneer in the cultivation of cacti and succulents was more than sensible, as well as experienced. Considering the difficulty of finding the loam of leaves (Lodi suggested leaves of beech or chestnut), that moreover must be well decomposed (and it may contain fungi and bacteria dangerous for the plants), this element can be replaced by good quality peat, sieved fine, without lumps and filaments. Too bad that over the years we have forgotten Lodi advice to focus everything on what for many is still the standard substrate of peat, lapillus and pumice in equal parts, standard enough to fit any kind and species of succulent.

In the following article now we see which is the best substrate for growing cacti and succulent plants based on my experience over the years with proofs and experiments on various mixtures. (…)

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