What Is Mushroom Compost? Benefits, Usage, FAQ


Many people mistakenly assume mushroom compost is primarily made up of decomposed or ground-up mushrooms, but that’s not true.

What is mushroom compost, and what makes it different from other types of compost?

Mushroom compost is a mix of the organic material in which table mushrooms grow. When growers harvest their crop, they gather up the remaining material, and it’s given away or sold commercially as a natural fertilizer.

In this article, I take a more in-depth look into the benefits and proper usage of mushroom compost.

I also answer common questions about this type of compost so you’ll know the appropriate way to incorporate it into your gardening routine.

What Do You Use Mushroom Compost For?

Soil additive – Mushroom compost is used just like other types of compost to enrich the structure of the soil and to add nutrients. The alkali content is ideal for certain plants and to neutralize highly acidic soils.

Lawn care – Grass grows especially well with mushroom compost. You can add the compost straight from the bag and rake over the grass for a thick, green lawn.

For bare spots, cover the area with the compost and work in the grass seed. There is no need to add topsoil, the mushroom compost feeds the seeds and controls moisture levels.

Increasing moisture retention – Mushroom compost is an ideal medium to fix overly dry or sandy soil. It has a better ability to hold water over other types of compost.

Garden booster – Tilling mushroom compost in with the soil in your garden makes it suitable for growing most flowers, vegetables, and fruits. The compost is also an excellent addition for well-drained potted plants inside and outside your home.

Related | Can You Compost Mushrooms?

Mushroom Compost Benefits

For those who have large gardens and want to avoid chemical fertilizers, mushroom compost is easy on the budget. The price makes it a cost-effective way to add nutrients in a natural way to your garden or landscape plantings.

Fresh mushroom compost tends to have a high alkaline content that is beneficial for acid soils. While this high alkaline can be troublesome for naturally alkaline and neutral soils, don’t let this deter you from using the compost elsewhere.

Mixing the compost with the existing soil is one way to diffuse the extra alkaline and salts and make it safe for use on:

  • Trees, especially fruit trees
  • Vegetables
  • Most flowers/flowering shrubs
  • Herbs
  • Lawns

Another benefit is reducing the time spent on watering plants. In areas where I find plants wilting by mid-day, I mix in a healthy portion of aged mushroom compost into the soil.

I need to water less often as the high level of moisture that mushroom compost retains keep plant roots hydrated longer.

Plants That Don’t Like Mushroom Compost

For all the benefits of mushroom compost, there are times you need to avoid its use. I have found certain plants cannot tolerate the high salt/alkaline levels that this compost mixture produces.

Plants like camellias, rhododendrons, summer-flowering heathers, and azaleas thrive in acidic growing conditions so they will fare poorly by exposure to the chalky minerals found in mushroom compost.

Members of the Pieris family of flowering shrubs will not tolerate mushroom compost. These evergreen shrubs are native to the eastern portion of the US. Many are part of the natural landscape in yards so be careful where you use mushroom compost as a mulch.

Blueberries and other fruiting bushes don’t like the chemical makeup of mushroom compost.

Root vegetables like carrots, potatoes, and parsnips also grow better without the use of mushroom compost.

Japanese maples are another plant that you should avoid mulching with fresh mushroom compost as the high alkaline will kill the specimen.

How To Make Mushroom Compost

While different growers use their own special blend of organic material in which to grow mushrooms, most use similar ingredients like:

  • Wheat or rye straw
  • Hay
  • Corn hulls and cobs
  • Horse or chicken manure
  • Grape scraps from wineries
  • Cottonseed, canola, or soybean meal

Mushroom farmers looking to grow a specific species may also add in other organic materials to the base. These materials can be peat moss, lime, gypsum, potash, ammonium nitrate, and urea.

Before this blend mixes with mushroom spawn to grow edible mushrooms, it’s left to compost for about a month. The heat that generates within this pile will kill off any seeds in the mixture and pathogens from the manure.

Once the mushrooms grow to maturity in this composted mixture, farmers remove them. The original growing medium is no longer suitable for a new crop of mushrooms, but has plenty of nutrients left to work as a general fertilizer and is sold off as mushroom compost.

Frequently Asked Questions

Will Mushroom Compost Burn Plants?

The high salt level in mushroom compost can kill seedlings and burn plants sensitive to the alkaline.

That is why gardening pros recommend always mixing mushroom compost equally with existing soil to prevent plant damage.

The method I use to reduce the risk of burning plants is to let the compost sit for several months before use. You can also till into the garden before winter, and by spring the salt levels should be fine for all plants.

Is Mushroom Compost Good For Tomatoes?

Yes, tomatoes do well in mushroom compost as the increase of calcium reduces the risk of blossom end rot that diminishes fruit production. Tomatoes love to grow in moisture-rich soil.

Spraying a mushroom compost tea on tomato plants can protect them from diseases like leaf mold and kills harmful bacteria.

Is Mushroom Compost Good For A Vegetable Garden?

Mushroom compost is a great way to increase production for most vegetable. Like tomato plants, the increase in soil moisture and nutrients aids in overall growth.

Most vegetables grow better in an alkaline soil, which mushroom compost provides. I use it in my vegetable garden every year with impressive results.

Is Mushroom Compost Good For Lawns?

Here is where mushroom compost is worth its weight in gold. Grass seed thrives in mushroom compost with its perfect blend of nutrients, moisture-retention, and mulch cover for quick, strong growth.

Grasses are not particularly sensitive to salt levels in the soil, so rake some mushroom compost all over your yard as a budget and environmentally-friendly fertilizer.

Is Mushroom Compost Better Than Cow Manure?

Mushroom compost and cow manure both offer a natural way to fertilize your plants. But, is one better than the other?

The effectiveness of gardening with mushroom compost is greater than cow manure because the compost has more ingredients that offer a better blend and balance of nutrients.

Cow manure can only offer the nutrients from the grass the cow ate, minus whatever the cow uses up to live and grow. Most cows graze on only grass and maybe a few types of other plants, so the nutrient variety is limited in the resulting manure.

How Much Mushroom Compost Do I Need?

For general planting of flower beds or vegetable gardens, the experts agree you should spread a layer of mushroom compost three inches deep over the area. Till the compost into the soil to around six inches deep.

For mulching, use two to three inches of mushroom compost to control weeds and hold in moisture. To enrich poor soil like clay, use a one-inch layer of compost. For sandy soil, use up to three inches to help with water retention.

To make easy work of calculating how many cubic yards, or bags of compost, you need to cover a certain amount of square footage, check out this handy compost calculator.

In Summary

Now you know what mushroom compost is and the benefits it brings to your home garden. It’s easy to see that using mushroom compost is a smart choice to enrich the soil and fertilize your plants naturally.

Experience the boost mushroom compost can bring to plant growth. Enjoy harvesting larger and more plentiful vegetables from your garden. Grow lush bundles of herbs and flowers.

When you use mushroom compost wisely, you can reap huge rewards.

I get a thrill when I see the exceptional results mushroom compost brought to my garden. Give it a try, and you might be pleasantly surprised as well!

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