The Benefits of Using Mushroom Compost in Your Garden

Mushroom compost, also known as spent mushroom substrate, is an excellent organic soil amendment for gardens. As more gardeners adopt organic and sustainable gardening practices, mushroom compost has become increasingly popular as a nutrient-rich, environmentally-friendly additive that can be used to improve soil health and plant growth.

What is Mushroom Compost?

Mushroom compost is made from the remnants of materials used to grow mushrooms commercially, such as straw, hay, corncobs, cottonseed meal, and chicken manure. After mushrooms have been harvested multiple times from these substrates, the remaining compost is pasteurized to kill any pathogens. Although it contains some mushrooms, mushroom compost is not fertile enough to grow edible mushrooms for consumption.

The main ingredients in mushroom compost are:

  • Straw or hay
  • Corncobs
  • Cottonseed meal
  • Gypsum
  • Chicken manure

Since it contains partially decomposed organic matter, mushroom compost adds valuable nutrients and organic carbon to garden soil. The rich, earthy medium provides an excellent habitat for beneficial microorganisms like bacteria and fungi. Mushroom compost improves moisture retention and maintains a neutral pH between 6.5-7.5.

Benefits of Using Mushroom Compost in the Garden

There are many advantages to using mushroom compost in your vegetable or flower gardens:

1. Improves soil structure and texture

Mushroom compost contains lignins and other fibrous compounds that improve soil aggregation. As compost granules bind to the soil, they create small clusters of stable soil crumbs. This crumb structure enhances air circulation, drainage, and root penetration in clay or compacted soils.

2. Increases moisture retention

The organic matter in mushroom compost acts like a sponge to hold water in the root zone longer after irrigation or rainfall. Compost improves moisture retention in sandy soils and reduces watering frequency.

3. Provides a slow-release source of nutrients

As microbes in the compost break down organic compounds, they release essential nutrients slowly over the growing season. Mushroom compost supplies nitrogen, phosphorus, potassium, calcium, sulfur, iron, zinc, manganese, copper and boron. The gradual nutrient release reduces the need for frequent fertilizer applications.

4. Promotes healthy soil biology

The organic matter and neutral pH of mushroom compost provide ideal conditions for beneficial soil microbes like bacteria, fungi, protozoa, and nematodes. These microorganisms decompose organic matter, fix nitrogen, and make nutrients available to plant roots.

5. Helps remediate contaminated or compacted soil

Adding mushroom compost can begin the process of bioremediating damaged soils. As microbes consume and transform soil contaminants, compost additions dilute toxins and improve fertility. The organic material also reduces bulk density and improves workability in compacted areas.

6. May suppress plant diseases

Some studies indicate mushroom compost may help suppress certain soil-borne diseases like pythium root rot and rhizoctonia. Researchers believe compost stimulates populations of disease-fighting microbes. More research is still needed, but compost shows promise for biological disease control.

7. Improves cation exchange capacity

The organic colloids in compost provide many binding sites for positively charged nutrients like calcium, magnesium, and potassium cations. This increases the soil’s ability to retain essential nutrients and prevent leaching.

8. Provides a source of humic substances

Humic substances like humin, humic acid, and fulvic acid form as microbes decompose organic matter in compost. These compounds enhance soil fertility and stimulate plant growth. Humic substances also improve soil structure and nutrient availability.

9. Buffers soil pH

Mushroom compost contains organic compounds that resist changes in soil pH, acting as a pH buffer. This neutralizing capability helps stabilize pH levels and reduce fluctuations that can stress plants.

10. Sequesters heavy metals

Organic colloids in compost can bind and immobilize heavy metals like lead, arsenic, and cadmium present in contaminated soils. This helps prevent heavy metal uptake in food crops.

How to Use Mushroom Compost in Your Garden

Mushroom compost is very versatile and can be used in several different ways:

  • As an amendment when preparing new garden beds, mix in 1-3 inches of compost to a depth of at least 8 inches. For in-ground plants, mix compost into the entire bed before planting.
  • To boost nutrients for existing plants, spread compost around the base of plants and gently work it into the top few inches of soil. Use up to 3 inches for trees and shrubs, and 1 inch for annuals.
  • When planting seeds or transplants, add a 2-3 inch layer of compost to planting holes and mix well with native soil. This gives roots an immediate nutrient boost.
  • As a mulch layer around plants to retain moisture and suppress weeds. Apply 1-2 inches on beds and up to 3 inches around trees and shrubs. Replenish the mulch layer each year.
  • To make compost tea, steep compost in water to extract beneficial microbes and humic substances. Use the tea to drench plant roots or spray leaves.
  • As an ingredient in potting mixes, combine with peat moss, perlite or vermiculite for containers and raised beds. Use up to 25% compost in the mix.

When applying mushroom compost, it’s important not to overload the soil with excessive organic matter. Aim to use about 1-3 cubic yards of compost per 1000 square feet of garden space. Always moisten compost after application to activate the microbes. Over time, the compost will slowly integrate into the native soil.

Growing Mushrooms in Compost

While commercial mushroom compost is not suitable for growing edible mushrooms, it is possible to produce mushrooms at home using compost or manure. The basic process involves:

  1. Building the compost pile: Make a compost pile with materials like straw, hay, horse manure, rabbit manure, and small amounts of nitrogen sources like seed meals. Maintain proper moisture and aeration.
  2. Pasteurization: Heat the finished compost to at least 140°F for several hours to kill pathogens, weed seeds, and insect eggs. Allow it to cool.
  3. Spawning: Introduce mushroom spawn, which contains mycelium, into the pasteurized compost to colonize it with mushroom mycelium.
  4. Casing: Cover the colonized compost with a protective layer of soil or peat to maintain moisture.
  5. Pinning and fruiting: As mushrooms form from the mycelium, maintain ideal humidity and airflow to support growth.
  6. Harvesting: Cut or twist mushrooms at the base of the stem when caps expand fully.

Popular mushrooms like oyster, shiitake, lion’s mane and wine cap can be grown at home with practice using compost or straw-based substrates. Proper pasteurization and sterile technique are key to prevent contamination.

Using Mushroom Compost in the Vegetable Garden

Mushroom compost is an excellent amendment for vegetable gardens, enriching the soil with organic matter and nutrients. Follow these tips for getting the most benefits:

  • Tomatoes – Mix 1-2 inches of compost into planting holes and use as mulch. Compost boosts yields, ripening, and flavor.
  • Peppers – Incorporate compost when planting and side-dress established plants. Improves yields and nutrition.
  • Eggplant – Mix with native soil in planting holes to encourage large healthy fruits.
  • Squash, melons, cucumbers – Add compost to mounded rows and planting holes to stimulate growth and help retain moisture.
  • Carrots, radishes, beets – Loose, fertile soil enriched with compost helps produce smooth, well-shaped roots.
  • Cole crops (cabbage, broccoli, kale) – Work compost into planting beds to encourage big healthy heads and improve flavor.
  • Beans and peas – Compost inoculates soil with nitrogen-fixing bacteria that help legumes grow and provide nitrogen.
  • Onions and garlic – The nutrients in compost encourage large bulbs and improve storage life.
  • Leafy greens – Rapid growth and higher nutrient levels from compost applications.
  • Potatoes – Burying seed potatoes with compost gives them nutrients and excellent growing conditions.

When preparing planting beds, adding 25-50% mushroom compost provides ideal nutrition for vegetables throughout the season. Side-dress established plants with a 1-2 inch layer annually.

Making Your Own Mushroom Compost

To make mushroom compost at home:

Materials Needed

  • 1 cubic yard of nitrogen source – manure, grass clippings, food waste
  • 1 cubic yard carbon source – straw, leaves, paper
  • Water source
  • Compost turner or pitchfork


  1. Layer nitrogen and carbon materials, keeping pile moist but not saturated.
  2. Turn or mix materials regularly to improve aeration.
  3. Monitor temperature – should reach 140-160°F before cooling.
  4. Finish composting in 3-6 months when dark, crumbly, earthy-smelling.
  5. Cure mature compost by allowing it to sit undisturbed for 1-2 months.
  6. Screen finished compost to remove any undegraded chunks.
  7. Use immediately or store in breathable containers.


  • Add more nitrogen sources if the pile doesn’t heat up.
  • Increase turning frequency or add coarse material if pile lacks airflow.
  • Turn pile more if temperature exceeds 160°F to avoid overheating.
  • Add water if the pile becomes too dry; turn more if too soggy.

With the right ingredients and some attentive care, it’s possible to produce quality mushroom compost at home. Blending different organic materials tailors the compost to your garden’s needs.


Mushroom compost is a versatile, sustainable soil amendment that provides a wide range of benefits to gardens and landscape plants. The decomposed organic matter contains essential nutrients and humic compounds that enhance soil fertility, structure, and moisture retention. Mushroom compost helps create an ideal soil environment to grow healthy, high-yielding plants. By supporting beneficial soil microbes and providing slow-release nutrition, mushroom compost improves plant vigor and vitality without excessive fertilizer requirements. Both conventional and organic gardeners can utilize this earth-friendly, nutrient-packed resource to increase soil health and plant performance.