One of the first issues I ran into as a new gardener was the concept of mulch. Everyone said to use it, but no one explained what it was. If you start searching “mulch” online, you’ll soon discover that almost anything can be considered mulch, as long as it can cover the ground. This list of common mulches includes wood chips, compost, grass clippings, rubber, plastic sheets, cardboard, landscape fabric, rock, and more. It’s pretty intimidating if you’re a new gardener.
The thing is, mulch is absolutely crucial for a healthy landscape, especially in a desert climate like Utah. Mulch reduces weed pressure, holds water in the soil, and (depending on what it is) adds nutrients to the soil as it breaks down. Here in Utah we’re either in a drought or recovering from one, so anything that can help us save water is going to be an important part of our landscape. Let’s break it down and talk about the pros and cons of each type of mulch in a typical backyard setting.
1. Wood Chips/Bark:
Description: Made from shredded tree bark or chipped branches, this mulch is one of the most popular for decorative and functional use. There are a wide variety of wood mulches, and cost can vary a lot. Bagged wood chips from the local hardware store are often dyed and may not be the most cost-effective or nutrient-rich option for your soil. You can also request a free chip drop from a local arborist. It’s free, but you are at the mercy of when and what they drop off.
Pros:
- Long-lasting
- Visually attractive
- Excellent for weed suppression
- Breaks down slowly, improving soil structure over time
Cons:
- Can rob nitrogen from the soil as it decomposes (especially if mixed into the soil)
- May attract pests like termites if placed too close to structures
- Can get into the grass and be difficult to remove
Where to Use: Wood mulches are best in flower beds and perennial beds, not in vegetable gardens.
2. Straw and Hay
Description: Hay is a type of dried grass that’s higher in nutrients and generally used for feeding animals. Straw is the leftover plant stalks from a grain product like wheat and rye. Both can be used for mulch, but typically straw is the better option. Hay is better used for animal feed and is more likely to contain seeds that could become weeds in your garden.
Pros:
- Breaks down quickly and adds organic matter
- Great for vegetable beds and pathways
- Helps keep soil cool and moist
Cons:
- Can blow away easily
- Needs to be replaced regularly
- May contain weed seeds if not carefully sourced
Where to Use: Straw is great for vegetable gardens. It can also be inoculated with mushroom spores, which improves water retention and can give you a mushroom harvest.
3. Grass Clippings
Description: Readily available from your own lawn, clippings are a quick mulch fix. When using grass clippings, be careful not to use clippings that have been sprayed with herbicides as that can damage or kill the plants in your garden.
Pros:
- Free and abundant
- Adds nitrogen to the soil as it decomposes
- Suppresses weeds when applied thickly
Cons:
- Can mat down and smell if applied too thickly
- Should not be used if treated with herbicides
Where to Use: Grass clippings are ideal for vegetable gardens. Start with 1-2 inches around your plants and replace as it breaks down or blows away.
4. Compost
Description: Decomposed organic matter that can be used both as mulch and soil amendment. Compost can be made from any organic matter; anyone can start composting from the food scraps and plant matter in their own yard. The quality of the compost depends on what has been added to it and how long it’s been left to age. Animal manure composts can be high in salts, which can be detrimental to the garden if your soil already has high salinity levels.
Pros:
- Rich in nutrients
- Improves soil structure and fertility
- Encourages beneficial microbes
Cons:
- Needs replenishing more often than other mulches
- May introduce weeds if not fully composted
Where to Use: Compost is great to use anywhere in your garden! It’s great to add a couple inches when you are first starting a garden plot to amend and enrich the soil, then add ½” to 1” every year after that to replenish those nutrients.
5. Leaves (Shredded or Whole)
Description: Fallen leaves from trees. It’s best to gather the leaves and shred them either with a leaf shredding machine or a mulching lawn mower before using them as a mulch.
Pros:
- Readily available and free
- Adds organic matter and nutrients
- Helps regulate soil temperature
Cons:
- Whole leaves can mat and block water/air
- May blow away if not shredded or watered in
Where to Use: In Utah, leaves take a long time to break down, so it’s usually best to add leaves to your compost to break down before you use them as mulch. Some people add leaves straight to their garden beds in the fall to protect the soil over the winter, then either till them into the soil in the spring or remove them and put them in the compost.
7. Rubber Mulch
Description: Made from bits of recycled tires, this mulch doesn’t decompose or add any nutrients to the soil, but it will allow air and water to get to the soil.
Pros:
- Very durable and long-lasting
- Doesn’t attract insects or mold
- Good for playgrounds and paths
Cons:
- Doesn’t improve soil health
- Can leach chemicals into the soil
- Not environmentally friendly
Where to Use: This type of mulch is best restricted to playground areas. It’s not a good option for vegetable or flower beds.
8. Gravel or Rock Mulch
Description: Inorganic option made from small stones, lava rock, or pebbles.
Pros:
- Permanent and low maintenance
- Excellent for heat-loving plants and xeriscaping
- Doesn’t decompose or attract pests
Cons:
- Can heat up soil too much in summer
- Doesn’t add nutrients to the soil
- Difficult to weed
- Difficult to remove once installed
Where to Use: Many people use a combination of rock and landscape fabric to keep weeds at bay in areas that need to be low to no maintenance. Rock is typically not a good option in most planting beds.
9. Landscape Fabric (Weed Barrier Fabric)
Description: A woven or nonwoven synthetic material laid over soil to block weed growth, often used under decorative mulches like wood chips or gravel.
Pros:
- Somewhat effective at suppressing weeds
- Reduces the need for chemical herbicides
- Helps retain soil moisture
- Acts as a barrier between soil and decorative mulch (especially useful with gravel or stone)
Cons:
- Does not break down or add nutrients to soil
- Can inhibit water and air penetration over time
- Weeds can still grow in the mulch layer above it
- Roots may grow into the fabric, making future removal difficult
- Can degrade and become unsightly if left exposed
Where to Use: Landscape fabric should be used sparingly and ideally only as a short-term solution as it will need to be replaced. It’s best used along pathways or in areas that will receive little to no maintenance for a short period of time, and it’s best to cover it with an additional layer of wood or rock mulch to improve the appearance and extend the life of the landscape fabric.