What Is Mushroom Compost and Why Use It

Just like regular compost, mushroom compost is often touted as black gold. It acts as both a plant fertilizer and soil amendment that can benefit your plants when used properly.

50/50 Mix Mushroom Compost/Screened Topsoil

This 50/50 mix is made up of 50% Mushroom Compost and 50% Screened Topsoil. It is the perfect choice for those customers looking to grow vegetables! The Mushroom Compost portion of this mix has the highest level of nutrients compared to any other product we have available. The high amount of nutrients comes from the horse and chicken manure which is aged into the mushroom compost. The Topsoil component helps to add structure and support to your garden bed so the roots of your vegetables stay strong and in place.

This product is available in bulk only. Try yours today! Your vegetables will thank you!

SKU: 50/50 Mix Mushroom Compost/Screened Topsoil Categories: Bulk, Compost, Soil

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What Is Mushroom Compost and Why Use It

Nadia Hassani is a a Penn State Master Gardener with nearly 20 years of experience in landscaping, garden design, and vegetable and fruit gardening.

Barbara Gillette is a Master Gardener, herbalist, beekeeper, and journalist. She has 30 years of experience propagating and growing fruits, vegetables, herbs, and ornamentals.

Unlike the name suggests, mushroom compost does not a contain any mushrooms—it is a by-product from mushroom farming; the growth medium of mushrooms that is removed after the mushrooms are harvested. The more apt name for it is mushroom soil.

Just like regular compost, mushroom compost is often touted as black gold. It acts as both a plant fertilizer and soil amendment that can benefit your plants when used properly.

How Mushroom Compost Is Made

The substrate in which mushrooms are grown is based on a mixture of different agricultural materials: hay, straw, poultry or horse manure, ground corn cobs and hulls, cottonseed or canola meal, cocoa shells, crushed grapes from wineries, soybean mill, peat moss, and other natural organic substances such as gypsum, lime, potash, urea, and ammonium nitrate. The exact composition of the growth substrate varies from grower to grower.

This mixture is composted for about 30 days at a temperature of 160 degrees Fahrenheit, in which any weed seeds, pests, or disease pathogens are killed. Afterwards, the mature compost is steam-pasteurized at about 140 degrees Fahrenheit to kill any pests and pathogens that could cause surface diseases. Then the medium is inoculated with mushroom spawn, or mycelium, and covered with a layer of sphagnum moss and ground limestone to support the mushroom growth.

Mushrooms are grown and harvested for about three to four weeks. At this point, the medium’s ability to sustain mushroom growth is exhausted and replaced with fresh mushroom soil for a new batch of mushrooms.

No longer suitable for mushroom-growing, the material is still full of goodness for gardeners. Some mushroom growers treat it with steam to kill pests, pathogens, and weed seeds. The substrate is then sold as bags or bulk, often labelled as SMC (Spent Mushroom Compost) or SMS (Spent Mushroom Substrate).

The Pros and Cons of Mushroom Compost

Mushroom compost is not an cure-all for your garden soil. It has benefits and disadvantages.

Aged, cured mushroom compost can be applied any time in the spring or summer. Application is most effective when the soil is fairly dry, which avoids compacting the soil while tilling in amendments.

Aged mushroom compost, either worked into the soil or spread around the base as mulch, can be added to a wide range of plants, including:

• Lawns, also as a top-dressing for newly seeded lawns
• Vegetable gardens
• Orchards
• Perennials, trees, and shrubs
• Container plants

Make sure to only use well-aged mushroom soil around rhododendrons, azaleas, camellias, and other members of the Heath family, (Ericaceae) because the high salt content can harm the plants.

For flower beds and vegetable gardens, evenly spread one to three inches of mushroom compost over the surface and till it into the top six inches of soil. For container plants, mix about one quarter volume of aged mushroom compost with three-quarters of potting medium.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. What Is Mushroom Compost? Oregon State University Extension Service.
2. Spent Mushroom Substrate. Penn State Extension.