What is the best mulch for a new garden bed? Mulch material comparisons for gardens and landscapes

THERE ARE A MILLION MULCH OPTIONS AND EVERYONE SAYS TO USE SOMETHING DIFFERENT

Wondering what is the best mulch for a new garden bed? Which to use? Here's a quick mulch comparison guide.

You'd think this would be the ONE area of life that is simple. There's a surprising amount of mulch controversy. And mulch myths. And even evil marketing of products that really don't work well at all. If your goal is to create a healthy, low maintenance landscape, I'm here to help.

My personal favorite materials are marked with an asterisk (*). I don't promise a comprehensive guide of all the mulch options in the world (because there are SO MANY mulch materials out there). But this covers the most common materials that you'll probably have access too, and enough context that you'll be able to consider your local options.

THERE'S NO SUCH THING AS A NO-MAINTENANCE LANDSCAPE (NOT EVEN CONCRETE)

Please remember: There is NO SUCH THING as a mulch material that 100% prevents weeds! Not even rubber coated plastic over rocks. Believe me, I've seen people try. Weeds are amazing.

Some materials are lower maintenance than others. For gardens and landscapes, the lowest maintenance while still keeping plants healthy? A deep enough application of an organic woody material (wood chips, bark). Organic materials decomposing on the soil surface are the best at preventing the majority of weeds.

But there will always be a few weeds to pop out here and there. Also, organic woody mulch materials will always need to be topdressed (a little bit re-applied) every few years.

The lowest maintenance mulch material? That's best at preventing weeds? Plants. A densely planted, well designed landscape is significantly less maintenance than anything other than concrete, once it is established. And even concrete needs periodic cleaning.

Just remember: there's no such thing as a no-maintenance landscape.

Arborist Chips*

By far the best mulch material for soil and plant health. Often can be sourced for FREE from local arborists. Diverse materials and sizes feed soil life and plants, while allowing water and air flow to plant roots. Only downsides: 1. It does need to be topdressed/ refreshed slightly more frequently than some other materials (approx. every other year). 2. When getting them for free, the volume you receive will often be a surprise.
Arborist chips are objectively the best for the plants and the soil. A deep application of arborist chips plus about a year is perhaps the best way to smother out weeds or lawn to create a new garden bed.

Small Fir Bark Nuggets*

My second personal favorite mulch material (after arborist chips). Small fir bark nuggets are large enough that they do not compact to form a water and air resistant layer (unlike shredded bark mulches). The fade to a natural brown color. They do not feed or improve soil to the level that arborist chips do. All bark mulches are more flammable than wood chips. Bark is naturally more water resistant than wood chips and dries out faster. This means they decompose slower, so small fir bark nuggets last longer in the landscape and do not need to be reapplied as frequently (every 2-3 years).

Medium/Large Fir Bark Nuggets

The same fir bark, larger chunks. The bigger the piece of mulch, the longer it will last in the landscape. However, if the pieces are too large, it can be difficult to get a deep consistent enough covering over the soil to prevent weed seeds. If plants are larger, and if there are large open spaces between plants, a medium or large chip size is a possibility. Keep in mind that you'll need to go deeper to get a full coverage (you'll still need multiple pieces deep and overlapping to prevent weeds). When establishing new plants or in smaller spaces, small fir bark nuggets are more realistic.

Cedar Chips*

A great choice for preventing weeds in gardens and landscapes, it is a MYTH that cedar chips inhibit the growth rate of plants. They can slightly decrease seed germination, but if you plan on sowing seeds, it's best to rake the mulch away, regardless. When it comes to preventing weed seeds from germinating, however, it is very effective. Cedar chips absorb water and are slightly less flammable than bark mulch materials. They last slightly longer than arborist chips due to larger size.

Dense Plantings*

Probably not a "mulch material" you were expecting, but a well designed and densely planted landscape is the lowest maintenance mulch material. Note that dense does not mean "messy" or "expensive" (it's all about good design). A densely planted landscape prevents weeds better than any mulched landscape. Many plants (not all) can be less flammable than wood and bark mulches. When you install a new landscape, you will need to select a material to cover the area until plants fill in. But as plants grow, you need less and less mulch over time.

Bark Dust and Shredded Bark

Fir bark can contain more splinters than hemlock bark. Bark dust or shredded bark mulches have their downsides. Fine bark mulches can settle and compact to form water and air resistant barriers, decreasing plant health (you can use a pitchfork to aerate mulch periodically, though it is a pain). Bark is naturally more flammable than wood chips (and bark dust dries out quickly in the sun) making it a great tinder. It does not increase soil health and fertility like arborist chips. If the aesthetics are worth the downsides, bark mulch is an acceptable mulch material.

Black or Clear Plastic

Black or clear plastic can be used to smother and "solarize" existing weeds or lawn, but is not a recommended addition to gardens and landscapes in other contexts. If you use it as mulch around landscape plants, it can heat up the soil, cut off air and water flow, and stress plants.
It is also possible to smother weeds or lawn with only a deep application of arborist chips. Plastic under another mulch material is a waste of your money. If you want to solarize weeds or lawn, do so with just plastic (for recommended amount of time, during the correct time of year, depending on what you are solarizing). Please not that solarizing can decrease soil health (it kills soil life). Then, apply an organic mulch material (wood or bark) to prevent new weed seeds from germinating. Plastic that has been notable soiled or degraded by sunlight cannot be recycled. Plastic also releases microplastics and their addition to the landscape is a consideration.

Rubber Mulch

Even deep rubber mulch does a poor job of preventing weeds. Notably more flammable than organic materials. Varying levels of toxicity, depending on the source. Emits a bad smelling odor when it heats up on hot sunny days. Companies hoping to make a quick buck do a great job at marketing this ineffective material, because it sounds like it will be indestructible. And what can grow through rubber, right? A lot. Worst of all, it is nearly impossible to clean out of a yard or garden once it has been spread across an area. I have spent many hours working to clean up this ineffective material, and I have had many clients do the same. It is neither practical nor ethical to use rubber mulch in landscapes or gardens.

Landscape Fabric/Cloth

Landscape fabric is only effective at preventing weeds for the first few years. Fabric soon becomes clogged with decomposing organic matter, and blocks water and air flow to plant roots. This does not always kill plants, but will slow growth and increase stress (which increases susceptibility to pests and diseases). Fabric can be used to smother weeds, but fabric does not prevent weed seeds from germinating. The material you put on top of the fabric prevents weed seeds from germinating. Consider removing, smothering, or even spraying weeds using another method, then mulching deeply with an organic material (like wood or bark) before installing plants. Fabric gets buried under decomposing mulch over time and is extremely difficult for future gardeners to remove. In different contexts, fabric and other materials can be used temporarily to smother weeds, but is not a recommended permanent addition to a garden. In other contexts, like under decorative dry creek beds, under pathways, or in agricultural settings, landscape fabric may be relevant.

Gravel and Rocks (as Mulch)

Surprisingly, weed seeds still germinate in gravel. In my experience, more so in gravel than in wood chips or bark. Gravel mulches absorb heat from the sun, heat up the soil, and can stress plants.
Rocks do not decompose and go away, but that als means they do not feed the soil. Organic matter (like leaves, dust, other plant materials) can get caught between rocks, decompose, and create little bits of soil over time, so be sure to keep rocky areas clear.
Note that I'm talking about mulching around plants. Gravel and rocks in pathways or decorative dry creek beds are different.

Leaves

I'm sure you've heard the saying "leave the leaves"! Leaves are a fantastic mulch material, though most will decompose quickly. They're great at building soil. However, if you're looking for a material that will consistently prevent weeds, begin with a deep application of a wood or bark material. If trees and plants drop leaves on top of your mulch, it's great to "leaf them be." Their color will fade quickly and they will decompose and help your mulch do it's job of preventing weeds. Large trees that drop deep leaves will prevent weeds on their own, though you may need to excavate landscape plantings a bit. Don't shred your leaves! Native insects sleep in leaves over winter, so the simple act of leaving them helps beneficial living creatures.

Cardboard/Newspaper

Cardboard or newspaper can be used to smother existing weeds or lawn, but is not a recommended addition to gardens and landscapes in other contexts. It is also possible to smother weeds or lawn with only a deep application of arborist chips.
If you use it as mulch around existing plants, it will cut off air and water flow, and will stress or potentially kill the plants. Cardboard and newspaper (even with tape removed) contains many microplastics and their addition to the landscape is a consideration.

Straw

Straw can be a great mulch material, though it decomposes quickly and is not something I recommend for low-maintenance landscapes. However, I have often used straw to mulch my vegetable garden beds. Be sure to ask if the straw is herbicide free! Many grain crops are sprayed with herbicides to kill them before harvesting, and residual herbicide can harm your garden plants. Note that hay and straw are NOT the same thing. Hay is more likely to contain seeds.

Trail Mix/Brush Hog Fuel

Weed prevention is similar to other wood chips, though not my favorite mulch material for landscapes and gardens. Trail mix or brush hog fuel often contains large chunks of wood, so a deep application is needed to create a consistent soil covering to prevent weed seeds from germinating. It's notably difficult to spread larger pieces around smaller plants. Materials are shredded, torn apart, and splintery (unlike arborist chips which are "chipped"), so not as comfortable to work with or as nice looking as arborist chips.

Dyed/Colored Bark

The dyes used to color mulches are not a concern (typically carbon-based dyes and iron oxide based dyes), but it is not uncommon for recycled wood to be used to make dyed mulches. Recycled old treated lumber can contain and leach harmful chemicals (fun things like arsenic), so it's important to learn the source of the wood before spreading it all over your yard. Or just stick with the undyed types.

Sawdust

Sawdust compacts easily and creates an air and water resistant barrier. Not recommended. Especially beware of sawdust from treated lumber products.

Sand

Sand on the soil surface does not prevent weed seeds from germinating, so it is NOT an effective mulch material in the landscape.

Compost

Trick option! Compost is not mulch. Compost is a great soil amendment (when needed), but it does not prevent weed seeds from germinating, so it is NOT an effective mulch material.

Pine Needles

Pine needles make a fantastic mulch! The only reason I did not add my asterisk for personal favorite materials is because I don't personally have experience purchasing them to use as a mulch. It is generally considered a myth that pine needle mulch will significantly affect the pH of your soil (more than just a few inches deep). As long as materials are un-shredded, the are unlikely to compact and create water or air flow problems.

Coconut Coir

Coconut coir can be used as a mulch material. However, unless you live near somewhere coconuts grow, it is generally expensive and impractical as a bulk mulch material.

Nut Shells

Various nut shells may be available for purchase in your area. If not available in bulk they may be expensive. However, they make a great mulch material. Be sure to mulch deeply enough! Two to four inches deep is a LOT of nut shells.

WHICH MULCH SHOULD YOU USE?

Here are my favorite mulch materials for low maintenance landscapes.

Arborist chips (free, builds soil, prevents weeds, needs topdressed more frequently)

Small fir bark nuggets (needs topdressed slightly less frequently, slightly more flammable)

Cedar chips (similar to arborist chips, not free, not as great for soil but close)

Pine needle mulch (slighty more acidic for first few inches of soil)

Remember: A dense, well designed landscape is truly the least maintenance, once established

FOR BEST RESULTS

Remove weeds properly before mulching (especially aggressive/invasive species). Mulch deeply. Typically 2-4 inches (5-10 cm) deep.
OR use an extra deep application of organic materials to smother out existing weeds or lawn, and wait 6 months to a year before planting into the space. We're talking 5-8 inches (13-20 cm) or more, depending on the aggressiveness of the weeds you are smothering. Arborist chips are by far the best material for this method. Learn more about smothering methods for turning weedy areas or lawn into garden beds here.