Mushroom compost is an excellent ingredient for soil amendment and provides a consistent supply of nutrients to plants. Still, this nutrient-rich resource is harmful to some plants, especially acid-loving plants, because of the alkalinity and salinity levels in the compost.
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What Is Mushroom Compost?
Mushroom compost is a combination of the organic material used for mushroom farming.
Once the farmers harvest the plants, they collect the remaining mushroom substrate and sell it commercially as compost.
The compost isn’t made of rotting or ground-up mushrooms as many would believe.
Is Mushroom Compost Good for All Plants?
Not necessarily. Mushroom compost has high salt levels that kill germinating seeds and destroy certain plants.
It can also cause leaf burn where the plant leaves wilt and turn yellow-brown. Leaf burn or leaf scorch occurs because compost salinity reduces water availability for your plant tissues causing foliage to seem burned at the edges.
Over-fertilizing your plants can cause leaf scorch because the fertilizers compose soluble salts.
Mushroom compost uses gypsum or lime as composting ingredients, increasing the soil’s alkalinity.
Acid-loving plants or ericaceous plants cannot thrive in such conditions because the compost neutralizes the soil acidity.
Still, many studies indicate that the average pH of mushroom compost is about 6.6, which is an ideal range for most garden plants.
Plants That Don’t Like Mushroom Compost
Some plants can’t handle the high levels of salts in mushroom compost, including:
Fruit/veggie plants
| Blueberries |
| Raspberries |
| Gooseberries |
| Cranberries |
| Rhubarb |
| Juniper |
| Radishes |
| Peppers |
Decorative plants
| Azaleas | Hydrangeas |
| Rhododendrons | Magnolia |
| Camelias | Daffodil |
| Aster | Ferns |
| Begonias | Gardenia |
| Holly | Heather |
| Iris | Nasturtium |
| Japanese maple | Salvia |
Plants That Like Mushroom Compost
Most flowering plants, herbs, and vegetables flourish when you add mushroom compost to the soil because they’re salt-resistant, while others require salinity to thrive.
Some of these plants include:
- Acacia
- Tomatoes
- Hibiscus
- Honeysuckle
- Junipers
- Lavender
- Lilac
- Agapanthus
- Aeoniums
- Butterfly weed
- Chinese silver grasses
- Columbine
- Gazania
- Prickly pear cactus
- Sea holly
- Sea thrift
- Ornamental clovers
- Polemoniums
How to Use Mushroom Compost?
You must mix mushroom compost with soil and never grow plants directly in it.
If you want to improve your soil quality, mix your compost in a ratio of one part mushroom compost to two parts garden soil.
You can also purchase ready-made potting soil mixed with mushroom compost in the right portions for your flower beds. For potted plants, your compost should make up a quarter of the soil volume in the container.
Still, mushroom compost is rich in soluble salts that can kill germinating seeds and young plants, especially salt-sensitive crops.
It’s, therefore, best to avoid applying the compost to young vegetables.
Instead, make compost tea by mixing one part of compost with four parts of water to neutralize the harmful effects of the salts and introduce microorganisms to your plants.