Mulch Guide: Types, Pro Tips and Where to Mulch

A bed of wood chip mulch deters weeds and helps a day lily's color to pop in backyard landscaping.

Mulch can be organic (leaves, wood, and grass trimmings) or inorganic (plastic and rocks). Our guide details mulch types and where to use them in your yard.

Let’s get started with what mulch is and how mulch helps your yard.

What is Mulch?

Trees have been providing their own mulch for centuries. Their leaves or needles drop to the forest floor to create a nourishing coat of organic matter above the soil.

Homeowners have plenty of mulch types to choose from — organic and inorganic mulch, wood or plastic, for example.

While mulch can be any material, we don’t recommend grabbing the nearest item to throw on your flower beds as mulch. Your favorite bathrobe, for instance, will not suffice.

How Mulch Helps Your Yard

Mulch:

  • Prevents soil erosion.
  • Protects roots from exposure and damage.
  • Retains soil moisture.
  • Increase soil temperature.
  • If organic, mulch adds nutrients to the soil.
  • Reduces weeding by controlling or suppressing weeds in your garden bed.
  • Helps water and air to penetrate the soil.
  • Makes your yard more attractive.
  • Provides winter protection.
  • Protects soil from drying in direct sunlight.
  • Reduces soil compaction.

What is Organic Mulch?

Organic mulches are plant material such as fallen leaves, grass trimmings, pine bark, straw mulch, wood mulch, or bark nuggets. All of these decompose over time and enrich the soil with nutrients and organic matter, allowing your plants to flourish.

According to the University of Georgia Extension, landscape waste, such as leaves, grass clippings, and trimmings, make up 20% of landfill debris. A better solution: You can put these organic materials to good use in your yard while also helping the planet.

Because organic mulch decomposes into the ground, you will need to regularly mulch your yard, flower bed or garden.

Like leaves, organic mulch can cost little or nothing. If you have a lawn mower that mulches your grass trimmings, you’re providing nutrients back into the soil as part of your regular lawn care.

With organic mulch, you may find the benefits of your plants receiving plenty of nutrients outweigh the costs of replacement mulch. If so, then opting for an organic mulch is the best choice for you.

Pro tips: Ensure your organic mulch is chemical-free and seed-free for the best results. Seeds will lead to unwanted weeds that compete with your plants for nutrients and moisture. Keep in mind that many organic mulches take up nitrogen from the soil. Homeowners may need to maintain their plants with nitrogen fertilizer.

The New Jersey Agricultural Experiment Station encourages homeowners to apply the right amount of mulch to avoid the damages excess mulch may cause plants.

What is Inorganic Mulch?

Inorganic mulches are often made of stone or plastics and are low maintenance. These mulches don’t take nitrogen from the soil, carry weed seeds, or need regular replacement.

Homeowners who prefer a permanent mulch are willing to pay for this advantage. Cost varies. You can buy rocks by the bag or truckload. Plastic mulch by the roll and rubber mulch you can buy by the sack at any home improvement store or garden center.

Disadvantages of inorganic mulches? Inorganic mulches don’t return nutrients into the soil, and stone mulches can settle deep into the ground. Stones buried in the soil will make any future planting or digging a challenge.

Best Organic Mulch Materials for Your Landscape

Bark

This mulch contains softwood or hardwood and is most often available as shredded bark or bark chunks. Bark mulch resists compaction and is very attractive as ground covers.

Some shredded barks decompose slowly, making them an excellent option for homeowners who prefer few replacements. Bark chunks also take time to decompose but are more prone to washing away than shredded bark.

Shredded bark is effective at suppressing weeds and is one of the top mulch types to use on slopes. Shredded bark will take the nitrogen’s soil when decomposing, so add fertilizer to help keep your plants healthy.

Pro tip: Shredded hardwood barks sometimes contain high levels of manganese. Keep in mind that manganese can be toxic to plants in soils with a pH below 5.0.

Where to mulch: This mulch is excellent for slopes. Bark mulch layers are 1 to 3 inches deep. When using this mulch for trees and shrubs, ensure to mulch the whole bed. Avoid mulching directly against the trunk. Instead, leave an inch of space between the mulch and trunk. This mulch works well in annual and perennial gardens. Avoid using bark mulch in vegetable gardens.

Wood chips

Many different types of trees make up wood chips. This mulch resists compaction and remains in place. Wood chips from sawmills or tree companies sell for little to no cost, but can sometimes contain seeds that will lead to weed problems.

Keep in mind that free or low-cost wood chips may not have aged. Mulch that has not aged forms organic acids when decomposing, which can be toxic to plants. For this reason, it is best to buy your wood chips from a reputable vendor who can guarantee high quality, aged wood, and no seeds.

Small wood chips will take nitrogen from the soil. Homeowners will need to replace the soil’s nitrogen with fertilizer.

Where to mulch: Apply 1 to 3 inches of wood chips around tree beds, shrubs, and perennial gardens. When applying around trees and shrubs, do not mulch against the trunk.

Sawdust

This mulch acidifies the soil around acid-loving plants such as rhododendron, magnolia, and blueberries, but weeds have an easy time sprouting in this mulch.

Sawdust will often cake, making it difficult for water to penetrate the soil. This mulch will also take nitrogen from the soil, so it is best to check your plants’ health. Use aged sawdust to help prevent nitrogen deficiency in the soil.

Where to mulch: A 3- to 6-inch layer of sawdust works best in the soil around acid-loving plants. Sawdust also makes an excellent mulch for walkways.

Straw

Straw makes an excellent winter mulch and mulch for the vegetable garden, but be sure to use straw rather than hay. Though straw may contain weed and crop seeds, hay will often carry much more.

Straw is an affordable mulch that has good weed resistance, conserves moisture, and insulates the soil. This mulch type will decompose over a short period and will need regular replacement.

Pro tip: Keep in mind that straw is highly flammable.

Where to mulch: Straw makes a great mulch for vegetable gardens, annual and perennial gardens, and newly sown lawns. It also works as a mulch around trees and shrubs in the winter.

Pine needles

Also known as pine straw, this mulch decomposes slowly and adds fragrance. Pine needles resist compaction and will stay in place due to their needles interlocking. This mulch enables air, water, and nutrients to penetrate the soil.

Where to mulch: Pine needles make excellent mulch for slopes, annual and perennial gardens, shrubs, and acid-loving trees.

Leaves

Leaves work best as mulch when coarsely shredded. Wind will blow whole leaves away, and finely shredded leaves will prevent water from penetrating the soil.

Leaves also are excellent at controlling weeds. They decompose quickly and will add plenty of nutrients to the soil.

Where to mulch: Shredded leaves are a desirable mulch for your turf, vegetable garden, flower bed, trees, and shrubs. Homeowners also can compost leaves to create a compost mulch.

Compost

This mulch is an excellent source of nutrients for your plants. Better yet, compost is the ultimate DIY project: You can make compost yourself. If your compost is dry, be sure you spread only a thin layer and top it with another mulch.

Where to mulch: Compost is a nutritious mulch for vegetable gardens, trees, shrubs, and flower beds.

Grass clippings

Grass clippings make a good weed resistant mulch. Create a 2-inch mulch layer with dry grass to prevent the grass from matting together. Fresh clippings will grow compact, creating a barrier that prevents water from reaching the soil.

Pro tip: Don’t mulch with grass clippings that you have treated with herbicides.

Where to mulch: Grass clippings are a nitrogen-rich mulch that works best in vegetable gardens.

Best Inorganic Mulches for Your Landscape

Black plastic

Black plastic provides excellent weed control, warmth, and moisture conservation, and it prevents rainfall and air from accessing the soil. Cut holes in solid plastic film to allow water to enter the soil and replenish the plants.

This mulch will lose its effectiveness when exposed to sunlight. Homeowners can bury the plastic in the ground and it should last for years.

Where to mulch: Black plastic works best as a mulch in vegetable gardens where irrigation systems are under the plastic. Avoid using black plastic around shrubs, as this mulch can harm a shrub’s long-term health.

Pebbles, crushed stone, lava rock

Pebbles, crushed stone, and lava rock make a permanent mulch that provides good weed control but makes removing twigs, leaves, and other debris difficult.

A layer of pebbles and rock reflects solar rays and will create a hot landscape environment for your plants. Rocks come in a variety of textures, colors, and shapes, making it a decorative mulch for your landscape.

Pro tip: Gravel can penetrate the soil, which can make any future diggings quite tricky.

Where to mulch: Do not use this mulch near acid-loving plants. Avoid applying it to areas where you wish to dig. Pebbles and rocks work well as a layer atop fabric mulches and where permanence is desirable, such as driveways, walkways, and foundation plants.

Landscape fabrics

Landscape fabrics, also known as geotextiles, let air and water penetrate the soil (unlike black plastic). To make geotextiles last longer, stay in place, and have a more attractive appearance, add a light layer of another mulch on top.

This protective second layer of mulch acts as a barrier between the fabric and the sun’s damaging rays. When using landscape fabrics, homeowners will need to remove weeds as soon as they appear. Otherwise, the roots will grow into the fabric and become difficult to remove.

Where to mulch: Landscape fabrics work best as mulch around trees and shrubs. Geotextiles won’t work well in vegetable gardens and flower beds because digging in your vegetable garden and flower bed will damage the fabric and make it ineffective.

When to seek landscaping help

If you’re tackling a major home project, such as planting trees and shrubs around a pool or putting in native plants and flowers in your front yard, landscaping pros near you can offer expert advice and make the whole job easier.

What they’ll tell you is that no one mulch does everything. Picking the best mulch for your yard often comes down to your preferences, where you plan to mulch, and the specific needs of your plants.

If you still have your heart set on using your bathrobe as a layer of mulch, it may not be what we recommend, but no one is here to judge. Well, maybe the worms.

Jane Purnell

Jane Purnell

Jane Purnell is a freelance writer and actor in New York City. She earned her B.A. from the University of Virginia and enjoys a warm cup of French press coffee.