We use mulch to cover bare soil, keep out weeds, regulate soil temperatures, create a protective ring around trees, and for its “finished” look. But what type should you use? Different mulches provide different looks and outcomes. Here, we help you sort it all out.
There are two broad categories of mulch – organic and inorganic. Organic types are plant-derived and will decompose over time – it does not necessarily mean that they are made organically. Inorganic types will not decompose; they are materials like rock and stone, plastic, and rubber.
Let’s look at organic mulches first. These include products made from trees, straw, pine needles, and even paper and cardboard.
Shredded Hardwood
Usually made from oak trees, shredded hardwood are the most popular type. Look for double-ground and even triple-ground products to achieve that fine-textured, smooth style.
Pros:
- Provides a uniform “finished” look.
- Dark color makes plants stand out.
- Suppresses weeds.
- A ring of mulch around a tree protects it from mower and string trimmer damage.
Cons:
- Changes color as it ages and decomposes.
- Will need replacement every few years.
- Can develop slime mold – which is not harmful to you or your plants, but can be very unattractive.
- Piling it on every year can create an unhealthy environment for your trees and garden plants.
Wood chips
This product is made from a variety of trees, all chipped to a uniform size. This is an excellent choice for a woodland path.
Pros:
- Low cost, sometimes even free from municipalities or tree service companies.
- Will break down and condition the soil over time.
- Suppresses weeds.
Cons:
- Raw wood chips can burn plants.
- It may be too rough and coarse-looking for some gardens.
Bark
Bark comes in a variety of sizes; the smaller the nuggets, the faster they will decompose. This product is often made from pine bark, but you can also find it made from cypress, fir and spruce, and other hardwoods.
Pros:
- Comes in different colors depending on the type of tree bark.
- A variety of sizes gives a variety of applications and looks.
- Suppresses weeds.
Cons:
- Doesn’t add nutrients to the soil.
- Pine bark is acidic (although this can be a benefit if you are growing acid loving plants).
Straw
Straw is best used as a temporary covering. Use straw to cover grass seed before it germinates, as a path through the vegetable garden, or to cover tender perennials in winter.
Pros:
- Inexpensive.
- Lightweight and easy to work with.
Cons:
- May attract rodent pests.
- It blows all over, and as such, it can be messy.
- It may have been treated with pesticides which may be harmful to your plants.
Grass Clippings
This is a mulch you make yourself! If you have a mulching blade on your mower, you can leave the grass clippings on the lawn and all the nutrients in the cut blades will be returned to feed your lawn. Another use would be to rake up the grass clippings and use them in your garden.
Pros:
- Free!
- Adds nitrogen to the soil.
Cons
- Decomposes quickly.
- It may contain weed seeds.
- Not very attractive.
- You shouldn’t use grass clippings treated with pesticides in your vegetable garden.
Leaf Mold
Also called leaf mulch or simply shredded leaves, this is crumbly, partially decomposed leaves. Rich and humusy, leaf mold is excellent for conditioning the soil and restoring nutrients. It makes a good winter cover for tender perennials and plants with a tendency to frost heave.
Pros:
- No cost.
- You can make it yourself by running a mower over fallen leaves.
- Adds nutrients to the soil.
- Protects plants from freeze-thaw cycles.
Cons:
- It takes about a year for leaves to age, so you’ll need space for that to happen if you don’t shred them.
- Needs frequent replenishment.
- Can blow away.
- Can mat if piled too deep.
Cocoa Hulls
Cocoa hulls are made from the shells of processed cocoa beans. It has a fine texture, a rich, dark color, and a wonderful smell. Use it in areas that are on the dry side as it can get moldy and only put down a one-inch layer.
Pros:
- Adds nutrients to the soil.
- Very attractive.
- Lightweight and easy to use.
Cons:
- Expensive.
- Decomposes quickly, requiring frequent replenishment.
- Develops mold easily.
- Poisonous to pets and wildlife if eaten.
Recycled (Enviro)
This mulch is made from old lumber scraps, construction debris, pallets, and old utility poles. It sometimes goes by the name “enviro mulch.” These wood scraps are milled to a uniform size and then dyed to a uniform color.
Pros:
- Less expensive than shredded hardwood mulch.
- You can feel good knowing you’ve kept this waste out of the landfill.
- Variety of colors available.
Cons:
- It may contain toxins, so don’t use it in vegetable gardens.
- Does not add nutrients to the soil.
Pine Straw
Pine straw mulch is simply the needles shed from pine trees. This product is very popular in the southeast United States, where it is harvested from under the trees.
Pros:
- A natural, renewable, and sustainable product with a small carbon footprint.
- It breaks down slowly, so it doesn’t need to be replenished as often as other organic products.
- The needles have a tendency to interlock, so they won’t (usually) be washed or blown away.
- Holds moisture.
Cons:
- It can hold too much moisture, which invites molds, mildews, and rots.
- It has a coarse look, may not be suitable for all gardens.
- Does not have as much nutrient value as other organic mulches.
- More expensive than other tree-based products.
Green
If you have too many weeds, that means you don’t have enough plants! Groundcovers and other low-growing plants can be used as mulches. They cover and shade the ground, which keeps weed seeds from germinating. They can be used to control erosion, especially on slopes. Cover crops can be used in vegetable gardens to add nitrogen.
Pros:
- Good for under and around trees, and in perennials gardens.
- It does not need to be replenished or refreshed (unless plants die).
- You can create a beautiful, intermingled garden with different colors, shapes, and textures of groundcovers.
Cons:
- It can become expensive, especially if covering a large area.
- Weeds can grow through groundcovers, but not as many.
Newspaper and Cardboard
These materials are often used under other mulches in vegetable and flower gardens. They can also be used to kill grass and other vegetation when building a new garden.
Pros:
- Free, or nearly so.
- Increases soil moisture.
- Feeds beneficial microbes in the soil as it decomposes.
- Excellent as a base layer in a no-till vegetable garden.
Cons:
- Chemicals in inks (especially color ones) can leach into the soil.
- Not very attractive if used alone.
- Can harbor slugs.
- Will blow away if not held down.
Compost and manure
These products are used mostly for topdressing – a thin one to two-inch layer can be put down in flower and vegetable gardens. As you work in the garden, these mulches become incorporated into your soil.
Pros:
- Conditions and feeds the soil, adds beneficial microbes.
- Inexpensive; you can make your own compost.
Cons:
- It can be smelly.
- Decomposes quickly.
- It may contain weed seeds.
- Fresh manure can burn plants.
Inorganic mulches will not ever decompose (at least, not in your lifetime), so they rarely need replenishing. They are low maintenance and have the ability to retain soil moisture.
Plastic and Landscape Fabric
Landscape fabric is used under inorganic mulches to create a barrier between the soil and the mulch. The fabric will help suppress weeds and allows air and water to reach the soil, but no nutrients are added to the soil because there are none to add.
Plastic should only be used as a soil sterilizer. You can put plastic down in a new garden and it will increase soil temperatures so that weeds and weed seeds are killed. This process is called solarization. Remove the plastic before planting because plastic does not allow air or water to reach the soil. Do not use it around plants!
Do not use plastic or landscape fabric under organic mulches. As organic products decompose, a layer of topsoil develops on top of the barrier. Weeds can grow in even this tiny sliver of soil.
Pros:
- It keeps products like stone and glass from sinking into the soil.
- Suppresses weeds when used under other inorganic mulches.
Cons:
- Does not add nutrients to the soil.
- Plastic does not allow water or air to reach the soil.
- Unattractive if used alone.
- Can rise up and become tattered and torn over time.
Stone and Rock
Decorative stone and rock can add a beautiful element to your home’s exterior. It’s very popular in xeriscapes and in alpine, rock, and gravel gardens. Limestone screenings for creating a path, pea gravel, pebbles, lava rock, river rock, and tumbled, polished stones are just a few of the options available.
Pros:
- Use in places where nothing will grow, such as under deep eaves.
- Good for creating a path.
- Large variety of shapes, sizes, and colors.
Cons:
- It keeps soil colder longer in springtime and can overheat the soil in summer. This can be harmful to your plants.
- It needs landscape fabric underneath.
- Will collect falling leaves and other debris and may be hard to keep clean.
Rubber
Rubber mulch is made from old tires that are shredded or chopped into nuggets. It’s a great way to give a second life to something that can only go into a landfill. It makes a soft landing when used under kids’ playsets
Pros:
- Long-lasting; doesn’t rot or fade.
- It doesn’t attract insects.
- It’s lightweight and is easy to work with.
- It is often dyed, giving the gardener a variety of colors.
Cons:
- Expensive.
- It can float away in heavy rains or be blown away in high winds.
- It may leach toxins into the soil – don’t use it in vegetable gardens.
- Difficult to dispose of when you no longer want it
Tumbled Glass
Recycled from bottles, jars, and windows, glass is tumbled until it is smooth and the pieces are uniform. The pieces can be as small as gravel or as big as your fist and come in various colors. Use it as you would rock or stone. Seven pounds of glass can cover one square foot to a depth of one inch. It creates a drier environment, so don’t use it with moisture-loving plants.
Pros:
- It gives a beautiful, sparkly look
- It lasts “forever” and rarely needs replenishment
- Lots of sizes, shapes, and colors.
Cons:
- Expensive
- It can be difficult to keep clean and shiny.
- It needs landscape fabric underneath.
Now that you know about the different types of mulch and how to use them see our article “How to Mulch” for information on best practices!
