What kind of soil do succulents use?
Today, I will introduce the experience of growing succulents, specifically what kind of soil to use for succulents. Here is a detailed introduction.
In China, especially among succulent enthusiasts, a lot of effort is put into soil mixing, which I personally believe is a misconception and not entirely correct. To quote a sentence from "Echeveria Cultivars": Echeverias can grow well in ordinary garden soil, and it would be even better with breathable, loose, and fertile soil.
As you can see, the issue of soil is not decisive; the key lies in the care. Currently, most of the succulent soil available in China is a mix of various planting materials (at least that's what I know). So, what role do these planting materials play in succulent soil?
1. Providing nutrition: This is mostly handled by garden soil and slow-release fertilizers. Peat can also play a role in slow-release fertilization, but it is recommended to "wash" the peat before use, as peat can easily change the soil's pH value.
I have tried using garden soil to grow succulents in Tianjin and Chengdu (both in the growing season). Oddly enough, the ones in Tianjin grew normally with proper water control and did not rot or decay, while the one in Chengdu was not so lucky. After a period of care, it quickly developed root rot and leaf decay. Although there was some soil hardening later on, the plant survived and grew robustly.
Why is this the case? Naturally, the humidity in Chengdu is much higher than in Tianjin. After watering, the garden soil does not dry easily, and the stagnant air causes anaerobic respiration in the roots, producing alcohol, which is harmful to plant cells and leads to root rot. If unlucky, the rotting wound can become infected with bacteria, causing the entire plant to die (the death is almost identical to what we call "drowning"). To avoid such a tragedy, we should prevent the plant's roots from being "suffocated" and find ways to make the soil looser and more breathable.
2. Breathable and loose: I believe that many misconceptions about succulent soil in China are in this area. Let's look at the planting materials that can make the soil breathable, loose, and prevent hardening.
Lava rock: Also known as lightweight rock, pumice, or planting stone, it has porosity, visible gaps, and strong water absorption and retention; because it is granular, it has good breathability when stacked. The disadvantage is that it is fragile.
☆Coconut bran: I use a lot of it... it's cheap and useful. Coconut bran is the fiber powder from coconut shells, a byproduct or waste of coconut processing (now used in horticulture, very eco-friendly, and very cheap). Its permeability and water retention are its characteristics, and its affordability is the most attractive (there are coconut bran bricks sold on TB, a small one can last a long time after soaking). Coconut bran is slightly acidic, which is beneficial for regions with alkaline water.
☆Vermiculite: Vermiculite can be used as a soil conditioner. With good cation exchange and absorption properties, it can improve soil structure, store water, and increase soil breathability and water retention, turning acidic soil into neutral soil. Vermiculite can also act as a buffer, preventing rapid changes in pH, and allowing slow-release of fertilizer in the growing medium, with no harm to the plant even with slight over-fertilization (good news for beginners). Vermiculite can also provide plants with K, Mg, Ca, Fe, and trace elements such as Mn, Cu, Zn (this role is not significant because you will mix in slow-release fertilizer). The downside is that vermiculite can easily turn to powder, but for succulents that need to be repotted every one or two years, I don't think it matters much, and it's very cost-effective.
Hakuryu soil: Personally, I think this soil is somewhat overrated. It is formed by the accumulation of volcanic ash and is the most widely used soil medium. It is also the most widely used cultivation medium in Japan. In simple terms, it is crushed volcanic rock, which is still beneficial for water storage and drainage and can provide trace elements.
☆Peat: Also known as peat, peat soil, black soil, or lignite. Sterile, non-toxic, and pollution-free, with good ventilation, light texture, water retention, and fertilizer retention. It can play a role in slow-release fertilization, and peat can be used as a humic acid complex fertilizer or directly as an organic fertilizer. I've said so much just to tell you why almost every succulent soil formula uses peat.
River sand: Very cheap and useful! Average water retention, good breathability, and reusable. It can be used, but the disadvantage is soil leakage.
Active carbon: Artificially granulated sintered carbon, containing no organic matter, with strong adsorption properties and a hard texture. Its function is only for breathability and water retention, and its performance is average.
I have also seen some rather unusual planting materials, mostly homemade.
Brick particles: Amazing! A genius-level thought process. Honestly, smashing bricks and screening them can yield good results, balancing water retention and hardness. But the breathability is not great.
Coal slag: The product of coal burning, with good breathability, average water retention, and requires soaking in water for a period to remove the "fire" (there are sulfides that can harm plants). It's actually very useful... I even saw someone use all coal slag to grow stones in his garden. PS: I haven't tried it yet, but I will experiment with it when I change the soil next year.
You can see that there are so many planting materials that can make the succulent soil loose, so you really don't need to be overly obsessed with a particular famous planting material. The ones marked with an asterisk are the components of the soil I use. I don't think there's anything to hide about this, as for the ratio... two-thirds garden soil, one-fifth peat, and the rest can be mixed with any one or several of the above,随意搭配. Some planting materials are prone to powdering, which can lead to soil hardening the following year, but for succulents that need to be repotted every one or two years, I don't think the harm is significant and there's no need to worry too much.
Also, regarding fertilizers, I believe slow-release fertilizers are sufficient. Overly fertile soil can lead to succulent stretching (see the article on stretching for more details).
The above is the complete introduction to the soil used for succulents, for everyone's learning and reference!