Mulch is often thought of as an optional or decorative element in the garden. However, it offers a number of benefits to gardeners, including moisture retention, improved soil structure, and weed control. Mulch is typically applied from mid to late spring, when the soil has warmed up and the threat of frost has passed. Some gardeners also apply a layer during the fall to protect their plants. Mulch is a cost-effective option recommended for those that experience weed growth or poor drainage.
Simply put, mulching is when you apply a layer of either organic or inorganic material to the surface of the soil. While raised garden beds already offer a variety of benefits that do not require the use of mulch, some gardeners chose to add it to give their plants an additional boost. When adding in mulch, it is important to take into consideration the type and amount of mulch used. This article explores the pros and cons to using mulch in raised garden beds and some types of mulch you can use.
Benefits to Using Mulch in Raised Garden Beds
From moisture conservation to weed deterrence, there are many benefits associated with mulching your garden beds.
Suppresses weed germination and growth.
Weeding can be a great bother, especially when they pop up all over the place like whack-a-mole. While raised beds already deter weeds from encroaching, mulch acts as a crucial weed suppressant, drastically reducing the amount of weeds in your garden. It also eliminates the use of chemical herbicides, which can be harmful to the environment.
One of the primary benefits of mulch is its ability to conserve moisture, which offsets the rapid drainage that occurs in raised beds during the summer. Both organic and inorganic mulches limit evaporation, and organic mulches absorb moisture. During periods of intense heat, mulch keeps plants from drying out and helps them tolerate drought-stress better. Pine mulch and wood chips are recommended for moisture retention.
Prevents Soil Erosion.
Subpar soil and environmental stress can cause the soil to become loose and erode. Erosion can be easily managed by applying a layer of mulch. Mulch slows run-off velocity by acting as an anchor to stabilize the soil. When faced with steep slopes, it can be used in tandem with other erosion prevention methods for optimal effectiveness.
Provides soil with nutrients.
Organic mulches such as grass clippings and leaves improve the structure of the soil by adding in organic matter and nutrients. This aids in improving soil aeration and drainage, along with moisture retention.
Cons to Using Mulch in Raised Garden Beds
Most gardeners agree that it is useful to mulch your garden beds, but there are also some drawbacks. Excessive mulch can suffocate your plants in a layer of impermeable material and cause them to die. While 2 – 4 inches suffices for most mulches, organic mulches only need around 2 inches. Finely textured mulches like shredded hardwood should be applied sparingly compared to mulches with coarser texture, such as pine bark nuggets.
As the result of anaerobic decay – decomposition without enough oxygen – mulch has a tendency to emit an unpleasant, pungent odor similar to vinegar, ammonia, or sulfur. High quality mulch should smell like freshly cut wood or earthy compost. Not only does rotting mulch smell bad, it can kill your plants. When this occurs, remove some of the mulch and turn it over with a fork. Make sure it is in a sunny area so that light from the sun can kill off any toxins that have accumulated.
Possibility of overheating.
While it sounds funny, mulches can overheat and spontaneously combust under certain atmospheric conditions. When mulch becomes too dry under thick layers, the heat trapped inside can build up and combust. Even if the chance of your mulch combusting is improbable, it can still overheat and cause damage to plants. To prevent this from happening, wet your mulch and place it away from your home. Combustible types include shredded rubber, pine needles, and pine bark nuggets.
By contrast, mulch can become susceptible to mold and fungal growths under humid, moisture conditions. Though they may look unsightly, they are not inherently harmful to your plants. One way to get rid of mold is to turn it over or loosen it with a rake to improve air circulation.
Can kill plants, especially trees and shrubs.
Despite its benefits, excessive layers of mulch can be detrimental to plants. When applied in a thick layer than allowed to dry out, it can become hydrophobic, acting as a water repellent. Instead of draining into plant roots, the water slides off, leading to a dearth of moisture. Mulch volcanoes – mulch piled around trees – can also condemn trees to a gradual, suffocating death.
Common Types of Mulch
If you find yourself conflicted about which type of mulch to use, then it's generally better to use organic mulch, which can prevent water evaporation, improve soil structure, and block weeds from infiltrating your garden beds.
Organic mulch: The most common type of mulch, organic mulches are derived from natural materials such as bark, grass clippings, and leaves. They are the preferred choice in vegetable gardens because of their ability to improve the soil quality and reduce evaporation in the summertime.
Inorganic mulch: Inorganic mulch consists of synthetic materials that don’t decompose, such as plastic, rubber, or even glass. Usually added for cosmetic purposes, they will last longer than organic mulches, reducing the replacement cost. Some also have added benefits; gravel helps with drainage and perlite helps keep moisture in the soil. Rubber mulch, the type often found in children’s playgrounds, is not recommended because it contains toxic chemicals, smells bad, and is generally not healthy for your garden.
Though the terms are often used interchangeably, compost and mulch are not the same. Mulch is used as a covering while compost is used as a soil amendment. If soil quality is an issue, use compost. Mulch is recommended to address any of the above: suppressing weeds, preventing erosion, or retaining moisture.