Benefits of mulch

Mulch is one of the best things you can do for your landscape. Mulch has many benefits throughout the year. Here are tips on the dos and don’ts of mulch.

In winter, mulch insulates soil. This provides a warmer environment for earthworms, microbes and other beneficial organisms in the soil. Warm soil allows these organisms to stay active longer into the cold season, helping to improve your soil. Mulch also insulates plants roots, helping them survive cold temperatures. And mulch breaks the force of heavy rain, reducing compaction and erosion.

In summer, mulch reduces plants’ water needs. Mulch insulates the soil, which helps to keep it from drying out. As our summers get hotter and drier, mulch is increasingly important to help keep your plants and trees from getting drought stress. Ciscoe Morris says that research shows having mulch over the soil profile in summer can keep the soil temperature at 75 degrees, even when the air temperature is 90 degrees. This is a huge difference in keeping the root system functioning properly.

Year-round, mulch greatly reduces weed growth by keeping sunlight from reaching seeds, thus preventing them from germinating. This reduces the amount of work you have to do to keep landscape beds looking good. Mulch also feeds beneficial soil life, helps prevent the spread of soil-borne diseases like anthracnose and black spot, and adds an attractive feature to landscape beds.

Dos of mulch

Do apply mulch every year to keep your plants healthy. Spring and fall are the best times to apply mulch because the soil is moist and weather tends to be more moderate.

Do use an organic mulch. Organic mulch includes natural materials such as leaves, straw, bark and other plant byproducts like cardboard or paper. These things break down over time, and will eventually be incorporated into the soil itself – providing nutrients in the process.

We like mulches that contain wood chips and compost. Medium-textured mulch is best. Fine particles tend to pack down and retain moisture, which then evaporates before reaching plant roots. Coarse-textured materials may be too porous to hold adequate amounts of water. See below for more details about organic mulches.

Do use a thick layer of mulch. The general recommendation is about three to four inches of mulch in a planting bed, depending on how coarse the material is. This is the minimum depth for good weed control. Anything less will not keep the weeds at bay.

Do use the right mulch for the job. For example, for vegetable gardens, you may want to use compost or organic straw for the mulch layer. Wood chips or bark are better for shrub beds.

Do weed before you mulch. Remove weeds from the soil surrounding the shrubs in late winter or early spring, when it is still naturally moist. Remove each weed plant entirely, including the roots, because established weeds can continue to grow through a layer of mulch.

Do remove by hand all weeds that manage to penetrate the mulch layer. Do that as soon as you notice the weeds. Pulling those few weeds on a regular basis will prevent weeds from overtaking the mulched area.

Don’ts of mulch

Don’t apply mulch too close to the trunk of trees and shrubs. Keep it at least a hand’s width away from the trunks of trees and shrubs. According to Penn State Extension, a good rule of thumb is to pull mulch three to five inches away from young trees and eight to 10 inches away from mature trees. Mulch that is too close to the trunk can suffocate its roots, and moisture can build up, encouraging diseases that decay wood.

Don’t apply too thin a layer. If you don’t use a thick layer of mulch, light can still reach weed seeds and it won’t be an effective insulator against heat, cold and rain.

Don’t use a synthetic mulch. Synthetic mulches are great for pathways but not a good choice for landscape beds. Mulches such as plastic sheets or landscape cloth don’t feed soil organisms, may keep the soil too moist (a problem in our damp climate) and are a pain to deal with as they break down. Do you really want to pick little bits of plastic from your landscape beds?

Organic mulches

Compost – Compost is well-decomposed organic matter. It could include yard and garden waste, food scraps and/or animal manure. It is great for retaining moisture, suppressing weeds and improving soil. Compost is very sustainable and environmentally friendly, since you are using materials that would otherwise go to the landfill. It breaks down quickly, so needs to be replenished more often than other types of mulch.

You can make compost yourself or purchase it in bags or bulk. Read about how to make compost at home from University of Maryland Extension.

Wood chips (arborist chips) – This bulky mulch is ideal for enhancing soil structure by improving drainage and making it more moisture retentive. You can often obtain wood chips for free from tree service companies. Many times the chips will contain leaves along with wood chips. This combination of greens and browns (nitrogen and carbon) is great for feeding the soil.

Bark – Coarse or medium bark lasts a long time. Fine bark can pack down to create a barrier that prevents water from reaching plants. We prefer composted bark, which has begun to break down, so will start feeding your soil right away.

Leaves – You can simply rake autumn leaves into your beds. If you shred them with a lawn mower before you add them, they will stay in place better and break down more quickly.

Mushroom compost – This alkaline mulch is light and easy to use. Given its high pH, it’s ideal for lime-loving vegetables, including brassicas like kale, cabbages and broccoli. Avoid using on lime-hating plants like rhododendrons, camellias and heathers.

Grass clippings – Dry or compost before using. Mix with other materials to increase porosity and reduce matting. A source for some nitrogen but also higher alkalinity, which may compromise nutrition.

Animal manure – A good source of nutrients. Compost before applying or plant damage (burn) may result due to high salt content. Ideally, should be mixed with a coarse-textured material.

Peat moss – We don’t recommend using peat moss in gardens because mining peat from bogs releases CO2 into the atmosphere, increasing climate change. In addition, it is not recommended as a top dressing because water will not penetrate when it is dry.

Straw – It is coarse-textured so it persists a long time, but can blow away easily unless mixed with other materials. While generally not suitable as a landscape mulch, it does provide winter protection as well as cover for grass seed. It works well in vegetable gardens.

Cardboard and newspapers – These are useful as sheet mulch. The sheet of cardboard or thick layer of newspaper creates a barrier that weeds have a tough time breaking through. As they break down, they will feed the soil. See more about sheet mulching below.

We can help 

In Harmony will begin applying mulch to our clients’ landscapes in March. Contact us if you’d like an estimate for your yard.

Find out more

In this video In Harmony co-owner Ladd Smith explains several types of mulch and their uses.