Wondering why your plants are not growing well, despite you giving them generous amounts of mushroom compost? Then you may be growing them in the wrong soil conditions. In fact, the addition of mushroom compost might even be making things worse!
Some plants naturally prefer an acidic environment for optimal growth. For example, many deciduous trees and evergreens like magnolias, blueberries, willows, and Rhododendrons love growing in acidic soil – and adding mushroom compost will turn the soil alkaline. This higher pH level will not help these plants thrive, and might even kill them in the long run.
We have compiled a short list of common plants that do not like mushroom compost. However, this list is not exhaustive, so make sure to do your own research before adding mushroom compost to your garden!
What is mushroom compost?
You have probably heard a lot of gardeners swear by the benefits of mushroom compost. But what is it? And how does it benefit many garden plants?
Mushroom compost is made up of organic materials like corn cobs, hay, hulls, horse manure, peat moss, and various other ingredients. This type of compost is usually used by mushroom growers as a slow-release fertilizer.
Depending on the brand, the ingredients of this compost might vary slightly. Generally, it requires around three to four weeks to decompose before being sold in bags. Many gardening and landscape suppliers sell mushroom compost since it is popularly used as a soil amendment for gardens and container plants. Mushroom compost is also used as a mulch to enhance the soil quality in vegetable and ornamental gardens.
Aside from the nutrients, it contains, mushroom compost also improves garden soil through its moisture retention capabilities. This means you can decrease your watering frequency while your plants still grow healthily. The only downside of this type of compost is that it can increase the salt level in the soil, which can cause dehydration and compromise yield quality. And, as previously mentioned, it also increases the soil’s alkalinity, which is really bad for acid-loving plants.
Why some plants do not like mushroom compost
Some plants do not like mushroom compost because of its high alkalinity. It has the ability to neutralize the acid content in the soil, and unfortunately, a lot of fruit bushes and ericaceous plants prefer moderately to highly acidic soil conditions. If you apply mushroom compost while growing these types of plants, your gardening efforts are less likely to succeed as the plants will not thrive in such an alkaline environment.
Additionally, using mushroom compost can increase the concentration of salt in the soil. This means that a lot of the moisture will be absorbed by the soil, leaving less water available for the plants. Hence, with increased salinity, your plants will also suffer from root dehydration and water stress.
Ericaceous or acid-loving plants must therefore not be given mushroom compost and should be planted in soil with a pH below 7. If you are not sure about the pH level of your garden soil, you can purchase a pH soil tester such as the Kensizer or Luster Leaf 1601 Rapitest Test Kit. If your soil is alkaline, you can add soil amendments like sulfur, ericaceous compost, a pine needle mulch, leaf mold, and acidifying liquid feeds to make it more acidic.
10 Plants that do not like mushroom compost
Although mushroom compost is nutrient-dense and beneficial for many gardens, not all plants love it! This is mostly true for ericaceous plants, which do much better in an acidic environment. If you are not sure whether or not your garden plants will benefit from your homemade organic mushroom compost, then do check our list below. Hopefully, you will find the answers you are looking for!
1. Azalea
Azaleas are a type of flowering shrub that thrives in well-draining, acidic soil. If planted in alkaline soil, they will starve to death! Azaleas need a soil pH of about 5.5 to 6.2 to grow healthily and maintain their bushy foliage. A soil rich in mushroom compost will turn them yellow and kill them over a period of time.
So, if you are growing an azalea plant, it is best to use acidic, loamy soil. Instead of adding mushroom compost, use ericaceous compost to achieve the right soil pH for this plant.
2. Berries
Berries also love acidic soil. Whether you are growing strawberries, blueberries, or any other types of berry, make sure that they are planted in soil with the ideal pH range. For example, blueberries require a pH between 4.0 and 5.3, while strawberries need about 5.5 to 6.5 to thrive. Instead of mushroom compost, you can use a generous amount of leaf mold or peat moss to achieve the desired soil acidity.
3. Salvia
Salvia plants, otherwise known as sage plants, are members of the mint family that bloom with colorful flowers. Although they can be easily cultivated in regular garden soil, these plants prefer moderately acidic, dry soils with a pH range between 5.5 and 6.5. To make the soil more acidic, you can add chelated iron, soil sulfur, or aluminum sulfate. Do not leave your salvia in waterlogged soil, as it will likely die from root damage.
4. Geranium
Geranium, also known as cranesbill, is a perennial shrub that deserves a spot in your hanging baskets or flower beds. Geraniums are loved by many gardeners for their colorful flowers that come in shades of pink, red, white, violet, apricot, and yellow.
These ornamental plants are easy to grow and do not require mushroom compost to bloom. Keep the soil pH between 6.0 and 6.5, and use slow-release fertilizer or vermicompost instead to stimulate flowering.
5. Juniper
Juniper is an evergreen shrub that grows best in acidic soil, preferably between pH 5.0 and 7.0. This plant is highly forgiving and will probably flourish even in poor soil, but is best grown in nutrient-rich soil. You can give it a boost with either homemade or commercial compost. However, just avoid mushroom compost as this will not be very beneficial. As long as your growing medium is well-draining and provides good aeration, your juniper should happily thrive without serious issues.
6. Lupine
Lupine is an attractive flowering plant that can grow up to four feet under favorable conditions. One of its growing requirements is moist, well-draining, loose soil. Although it can thrive in highly acidic soil, this tall, spiky flower grows best in a neutral or slightly acidic medium.
Lupines also do not require a lot of fertilizer, as too much can increase leaf growth at the expense of flower production. However, if your growing medium is slightly alkaline, then applying an acidifying fertilizer will be beneficial.
7. Gardenia
Gardenia, also known as Cape jasmine, is an evergreen praised for its dark, glossy leaves and strongly scented white flowers. If you have fallen in love with its beauty and want to grow one in your garden, then you should know that it loves acidic soil with a pH between 6.0 and 7.0. Hence, it is best to avoid mushroom compost if you want to grow this beautiful flowering plant to its full potential.
Gardenias also need lots of space to avoid root competition. You can add perlite or pumice to the soil as well, to improve its drainage. Adding mulch like chopped wood or pine straw has proved helpful to increase moisture, boost soil nutrients, and prevent weed growth.
8. Heather
Heather, also called Scotch heather, is another evergreen flowering shrub that prefers an acidic environment. This classic garden flower loves composted bracken or rotten leaf mold as a nutrient source. If you want to see its flowers bloom beautifully, we highly recommend feeding it with a slow-release fertilizer and keeping it in an area that gets lots of sunlight.
Remember that this plant can be highly tolerant of poor, rocky soil, provided the soil is acidic – preferably around 6.5 or below. If your garden soil is neutral or slightly alkaline, you can increase the acidity by adding damp peat moss. Avoid using mushroom compost as this will make it alkaline.
9. Camellia
Also known as the queen of the winter flowers or ‘rose of winter, camellia flowers are highly sought-after for their lush blooms and thick, glossy foliage. These plants are also known as tea plants since they are harvested and used for caffeinated teas. The great thing about these beauties is that they are not very high-maintenance plants. As long as you provide them with an adequate growing environment, including neutral or slightly acidic soil, they will thrive and bloom!
Adding mushroom compost can impede the growth of your camellia, as it will increase the salt in the soil and make it more alkaline. Instead, try to keep the soil within a pH range of 5.5 to 6.5 and slightly moist. Add composted bracken, pine needles, or leaf mold to make the soil organically rich in nutrients.
10. Magnolia
Magnolias are a genus of flowering trees and shrubs that produce large, fragrant flowers that can be white, purple, yellow, or pink, depending on the species. Due to these unique, star-shaped flowers, they are a landscaping favorite among many growers.
If you want to grow magnolias in your own backyard, you need to make sure that the soil pH is between 5.5 and 6.5. Thus, you should avoid mushroom compost that will increase the soil’s alkalinity. Although magnolias are sufficiently adaptable to grow in clay or sandy soils, they are best grown in well-draining, moist soils to achieve the best blooms.
Conclusion
Mushroom compost is rich in organic matter and nutrients that support the healthy growth of your greens. However, not all plants like mushrooms compost since it can increase both the alkalinity and the salinity of the soil. If you are growing acid-loving plants, it is best to avoid mushroom compost and use other soil amendments to enrich your soil.
Image: istockphoto.com / Lilylian12