Warning: Why Mushroom Compost is Not Ideal for Succulents

Mushroom compost is a great soil amendment for many plants. However, it is not recommended for cacti and other succulents because of its high water retention. Succulents thrive in dry conditions, and keeping their feet wet can cause root rot and other fungal infections.

Before I explain everything in detail, let’s first understand what mushroom compost is and some of its benefits.

Despite its name, mushroom compost doesn’t contain any mushrooms. It is a by-product of mushroom farming. You may call it spent mushroom growth media because it’s obtained after the mushrooms are harvested.

This compost typically ranges in color depending on the age and material used. When fresh, it appears lighter in color with more visible straw. On the other hand, it looks darker when aged. Although fine-textured, unscreened mushroom compost often contains clumps.

Why use mushroom compost?

Just like the regular compost manure, spent mushroom compost is often used as a plant fertilizer and soil amendment. It has many benefits for plants that don’t mind wet soil. 

Spent mushroom compost can be a great source of different nutrients, including nitrogen. Its high calcium content makes it especially useful for growing fruits and vegetables. So, it’s your best bet when growing tomatoes and other plants that need high amounts of calcium.

Mushroom compost can also improve soil structure as it degrades over time. The straw and other materials in the media aggregate the soil, improving aeration and water retention. To benefit from this, it’s recommended to apply when the soil is fairly dry to avoid soil compaction. 

When applied on top of the soil, this compost can also act as a mulch, cooling the plants’ roots during a hot summer. 

Why mushroom compost is not ideal for succulents

The following are disadvantages of using mushroom compost for growing cacti and other succulents.

It can cause root rot

As I said, mushroom compost has a great level of water retention ability. Using it as a fertilizer or soil amendment can be detrimental to succulents and other plants that don’t like wet roots. As with overwatering, this compost can cause root rot and other fungal problems.

Root rot develops when excess moisture in the soil stops air from circulating in the soil. roots. This causes plant roots to suffocate and die because of insufficient air. Rotten roots cannot take up moisture and nutrients, and this makes the rest of the plant starve to death.

Fungal infections can also occur when the soil is kept too moist. The damp conditions are ideal for the growth of bacteria and fungi. So, mushroom compost is such bad news for cacti and other succulents.

It does not contain beneficial microorganisms

Spent mushroom soil is often sterilized before it’s sold as compost. This is basically to get rid of pests, weeds, and diseases. The pasteurization process also kills beneficial insects. This renders the material less beneficial to your plants.

Beneficial insects such as dung beetles, ants, termites, and springtails help in aerating and improving the structure of the soil. They are also important agents for breaking down organic materials in the soil.

May compact overtime

Over time, mushroom compost may cause soil compaction. This can greatly hinder drainage and aeration. Succulents and cacti need extremely well-draining, loose, sandy soil. Your best bet is to use sandy, gritty composts with a small amount of organic matter.

Final thought

In most cases, I prefer making my own succulent compost. I mix 1 part loam by volume with 1 part sharp sand and 1 part fine horticultural grit. This gives me a medium that maintains drainage and aeration, preventing excess moisture around the roots of the succulents.