The Importance of Mulch

Mulch can be a gardener’s best friend. It adds visual appeal to the landscape as well as providing many benefits to the plants.

Most gardeners agree that mulch makes any garden look better. Mulch is a form of ground covering and is used around trees and shrubs, along either side of the driveway, around the house foundation, under hedges, in vegetable and cutting gardens or anywhere that you want to cover bare earth.

From a design standpoint, mulch adds continuity to landscape beds within the yard, helps to make a newly planted gardens look fuller, and softens the line between garden and grass.

But mulch is far more than just a pretty ground covering. – It’s a real garden workhorse! Mulch deflects the sun and keeps moisture in the ground which keeps the soil cooler in the summer. During the winter months, mulch acts like a big, warm blanket insulating the earth and plant roots. Because mulch is organic, it will naturally break down and decompose over time. This creates wonderful compost which adds nutrients to the soil. Rich soil attracts earthworms which help to further enrich the soil. Finally, mulch helps to keep down weeds and unwanted grass.

Choosing a Mulch

Because there are so many different mulch products available it is difficult to know which ones are best. Basically, there are three types of mulch: plastic mulch, real mulch and stone mulch. Let’s consider all three.

Plastic Mulches

Plastic mulches usually come on a roll and are sold as "landscape fabric" or "plastic weed barrier." Because they are made from plastics and are not organic they do not provide nutritional benefits and are not necessarily environmentally correct. They are effective weed barriers, however.

Nonporous sheets of black plastic are not recommended for use in the garden because, while they are very effective at keeping weeds from coming up, they do not allow water to penetrate through to the plant roots.

Porous landscape fabrics allow rainwater to penetrate the soil. They work fairly well at keeping the weeds at bay. Landscape fabric is terrific to put down before installing a brick or stone patio or walk, under driveway stone, and under mulched paths and play areas.

Real Mulches

The real organic mulches are the best because they are lovely in the garden as well as functional. Although they decompose quite rapidly and need to be replenished often (about every season), it is this very decomposition which adds nitrogen to the soil and improves its structure.

We recommend shredded hardwood mulch for all planting areas. This mulch is made from shredded bark and has a good brown color – like dirt. We prefer shredded bark to bark chips and nuggets because it breaks down more quickly and improves our area’s infamous hard clay soil. If you prefer the look of chips or nuggets, spread the shredded mulch down first and then cover it with a layer of decorative mulch.

Wood chips can also be used as mulch. While wood chips are less expensive than bark mulch and can often be obtained for free, it is not nearly as attractive as bark and tends to have a yellowish color which looks unnatural in the landscape. Wood chips are a good, economical cover for large vegetable and cutting gardens, and play areas and paths.

Do not use freshly ground wood chip mulch around any plants until it has had an opportunity to age (usually 8-12 months). Fresh wood chips rob the plants of nitrogen which often results in the death of plants.

While bark mulch is the most common real mulch, some gardeners use salt hay, pine needles, coco beans, and even peanut shells, sawdust, seaweed, buckwheat hulls and cranberry vine!

Stone Mulch

Gardeners who either dislike the appearance of bark mulch or who are creating a specific design statement often use stone mulch. While stones do cover the soil and provide a bit of weed control, they do not improve the soil. Stone mulch, especially river rocks, can add beautiful color and interest to a garden. It is difficult to create a design incorporating white marble chips without making the garden look like a fast-food restaurant. White stones can also reflect heat onto surrounding plants causing sun scorch. In general, stone is expensive and difficult to work with.

Too Much of a Good Thing?

While spreading real mulch is one of the best things a gardener can do to benefit plants, piling up too much mulch can end up killing plants! Never use more than 3" of mulch around trees and shrubs. Thick layers of mulch will obstruct root development. If the mulch in the garden has turned into an impenetrable hard mat, there is too much mulch built up. You will need to either remove the mat layer or break it up with a garden fork. Also, if mulch is piled up next to the trunk of a tree, it will soften and rot the tree bark creating easy access to disease and insects. If there is too much mulch in the garden remove the old mulch before adding new. Old mulch can be added to the compost pile or worked into new garden beds.

What is That Disgusting Stuff?

Because real mulch is organic it will break down and decompose, creating rich garden soil. Rich soil combined with lots of warm, rainy weather is an environment that may cause fungus to grow. There is one particularly disgusting- looking fungus that looks, quite frankly, like yellow/orange vomit. While it looks awful, it is completely harmless. It can be removed with a shovel or it can be left to disappear on its own.

Resource Center