I think all gardeners can agree on one thing: mulch is essential! Good mulching practice saves water, naturally controls weeds, enhances soil fertility and plant health, and spiffs up the appearance of a space. Yet everyone has varying opinions on what type of garden mulch they prefer to use. Straw, compost, bark, leaves… there are many different mulch materials to choose from! So, what kind of mulch should I use in my garden, you ask? Well, it depends – on your individual needs, budget, space, aesthetic, type of garden, and what materials are most available to you.
This article will explore the pros and cons of 8 popular types of mulch. We’ll look at factors such as cost, durability, appearance, unique benefits, as well as potential risks or drawbacks. Then, you can make an informed decision about what type of mulch is best suited for your garden space. Or, a combination of many mulch materials – like we use!
If the concept of mulching is new to you in general, be sure to stop by our Mulch 101 article. It digs deeper into the benefits of mulch, the living soil food web, and best practices of when and how to apply mulch in your garden.
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Organic vs. Inorganic Mulch
Garden mulch options can more or less be broken down into two categories: organic or inorganic mulch products. Organic mulch includes natural materials such as leaves, straw, bark, pine needles, and other plant byproducts like cardboard or paper. These things break down over time, and will eventually be incorporated into the soil itself – providing nutrients in the process.
On the other hand, rock, stone, lava rock, and man-made products like plastic sheeting, rubber bark, or geotextile landscape fabric are all examples of inorganic mulch materials. Those types of mulch are usually more durable, and thus need to be replenished less often or not at all.
Keep in mind that the designation of organic versus inorganic here is only a matter of chemical make up – if the materials contain carbon or not. It doesn’t necessarily mean that all ‘organic’ mulch types are ideal to use in a garden that follows non-toxic organic gardening practices. For instance, some bark products may be dyed with chemicals, or straw sprayed with herbicides. On the flip side, rock is technically ‘inorganic’ but is totally natural.
Types of mulch we’ll explore today:
- Bark mulch or wood chips (including rubber bark)
- Gravel, stone or rock
- Cardboard, paper or burlap
- Other plant matter
- Plastic sheeting or landscape fabric
Distinct areas in your garden may call for different types of mulch. For instance, you may choose to use one material in your vegetable beds, another around trees or in flower beds, and something else in pathways. If you look around our garden, you can quickly see that we utilize at least four or five kinds of mulch throughout our space.
Compost is our favorite type of mulch to use in our raised garden beds. Not familiar with compost? Essentially, compost is any well-decomposed organic matter, including plant material and/or animal manure. Compost may be homemade, or purchased in bags or bulk. Learn about 6 different ways to compost at home here.
- Compost works triple-duty to reduce evaporation, insulate plant roots, and nourish the soil food web. In addition to acting as mulch, it is one of the primary natural fertilizers we use in our garden!
- The fluffy, fine texture and high nutrient content makes compost a great choice for vegetable gardens, flower beds, herb gardens, and containers. It is easy to work and plant around.
- Compost is pollinator-friendly, as ground-dwelling bees don’t mind burrowing through it like other more chunky material.
- Made from food, landscape, and animal waste otherwise destined for landfills, compost is incredibly sustainable and environmentally-friendly.
- Compost mulch decomposes quickly, and thus needs to be replenished more often than other types of mulch. We top off our raised beds with fresh compost twice per year, during our seasonal crop changeover and amendment routine.
- It may not suppress weeds as effectively as other mulch options, unless applied in a substantially thick layer.
- Improperly-composted or fresh animal manures may contain excessively high levels of nitrogen and is harmful to plants. Be sure that any animal manure compost you use has been well-aged. Furthermore, manure from dogs, cats, or pigs should be avoided altogether as they can carry pathogens that are harmful to humans.
2) Bark Mulch or Wood Chips
Bark or wood chips come in many forms, such as large bark nuggets, small bark, wood shavings, or shredded bark – also known as gorilla hair. Bagged bark products are readily available at any garden center. Bulk bark or wood chips should also be easy to find, through your local landscape supply company or tree trimmers.
Rubber bark or shredded rubber is a synthetic bark-size mulch product. I decided to not give it its own designated section in this article because I don’t believe it has a rightful place in a home garden. Made from shredded tires, rubber bark does give a waste product a second life. However, it is known to leach toxic chemicals that are harmful to the soil, plants, and nearby water resources.
- Can be fairly inexpensive, especially if you’re able to source bulk bark. Call around! Many municipalities or tree trimming companies even offer freshly ground wood chips to homeowners at no charge.
- Bark mulch is a very natural organic mulch option, as long as you avoid dyed/colored bark.
- Eventually breaks down to provide nutrients to the soil, and improve soil structure.
- When applied in a thick enough layer, bark does a good job at suppressing weeds.
- The variation of wood mulch products in size and styles makes them suitable for a wide range of landscaping applications – such as using fine shredded bark or wood shavings around delicate veggies and flowers, and chunky bark in pathways or borders.
- Because it eventually breaks down, bark mulch does have to be replenished every so often. The frequency varies greatly though, depending on your climate and the size or type of bark mulch used.
- Decorative colored bark may have been treated with chemical dyes, making it unsuitable for organic edible gardens. (Though some are colored with non-toxic dyes.)
- Buying bagged bark to mulch large spaces creates unnecessary plastic waste. Most landscape supply companies will deliver and drop off as little as half a yard!
- Pine bark is more acidic and takes longer to break down than hardwood mulch like cedar, fir or redwood, so is better suited for pathways or around trees than directly in veggie or flower beds. It can also be used on top of garden bed soil, but I would avoid mixing it in – unless you need to reduce the pH of alkaline soil. Cedar bark is known to be toxic to chickens, so avoid using it around your flock’s range space or coop.
- Native ground-dwelling bees and bumblebees will not burrow through dense bark. Leave some exposed soil or choose compost mulch to promote pollinator-friendly gardens.
Does bark mulch leach nitrogen from the soil?
Bark, wood chips, and other wood mulch products get a bad wrap for ‘robbing’ nitrogen from the soil. However, it doesn’t actually take nitrogen away from the soil. What happens is this: when fresh bark material is added to soil, there is a surge of activity in the soil-dwelling bacteria that are part of the nitrogen cycle. They turn their attention to breaking down the bark instead of continuing their work in the soil. The nitrogen is therefore temporarily ‘tied up’.
Yet as the bark is broken down, those bacteria and nutrients are returned to the soil. Furthermore, the nitrogen shift or tie-up is strongest when wood products are mixed into the soil, and especially new soil. There is far less impact when bark mulch is applied on the surface of established soil. In that case, the nitrogen tie up only occurs on the very top layer of the soil (well away from plant roots) and is part of the reason bark mulch is effective at suppressing sprouting weeds.
In all, there is only a minor and temporary disruption of available nitrogen to your plants. Freshly-ground wood chips cause more nitrogen tie-up than dry/aged bark products, so if you’re concerned about it, stick to applying fresh chips only in pathways or other open areas.
The most common types of straw mulch are wheat, barley, or oat straw. Don’t confuse straw with hay! Straw is a dry byproduct of grain crops. It usually contains very few seeds, but is possible to have some. On the other hand, hay is grass cultivated as animal fodder and very often contains weed seeds (sometimes quite noxious ones) – which will sprout and create a mess in your garden. No Till Growers has an excellent article about navigating the use of hay as mulch, if you’d like to learn more.
- Straw is inexpensive and widely available.
- It is lightweight (once separated from the bale) and easy to work with.
- Decomposes to provide fresh organic matter and nutrients to the soil.
- Straw may have been treated with pesticides or herbicides, which are then introduced to your garden. I have seen established plants wilt and die the day after contaminated straw mulch was applied around them!
- Some straw may also contain seeds, adding to your weed issues rather than reducing them. Seek out organic (pesticide-free), seed-free straw mulch for your garden.
- Because it is so light, straw can be messy and easily blow around in the wind. It will also need to be replenished every season.
- Straw provides an excellent hiding space for pest critters and insects near your plants. This is an issue with many types of mulch, but straw is an especially prime habitat.
4) Gravel, Stone or Rock
Pea gravel, lava rock, river rock, or crushed granite… There are numerous rock and stone options to choose from. I consider gravel more of a landscaping product than a mulch, but it can function as both! We use quite a bit of gravel (3/8″ green rock) in our front yard garden pathways, along with large cobblestones for perennial bed borders.
- Rock gravel is one of the most durable, long-lasting mulch options. After the initial purchase and installation, gravel should not need to be replenished like other types of mulch.
- Because of its weight, most gravel mulch doesn’t easily get disturbed by wind or rain.
- It can make a space look very clean, sharp, and attractive.
- Great for pathways, between garden beds, in open spaces, or in xeriscaped gardens. Not suitable for vegetable beds, flower beds, or directly under trees.
- Gravel, rock and stone products are often more expensive than other mulch options.
- It is heavy to work with, and fairly permanent in nature.
- Gravel doesn’t feed the soil like organic mulch materials do, though it can offer some protection.
- While it provides insulation and prevents evaporation, rock can create undesirable or excessive radiant heat – especially in hot climates.
- Without the use of gravel stabilizers below, smooth pea gravel moves and sinks when you walk on it, which is not ideal for some people. Loose rock can make using a wheelbarrow or garden cart challenging in the space. Other types of gravel (those with more jagged edges) lock in place better, providing for added stability as well as better weed suppression.
Free top-notch mulch, anyone? Oh, how I wish we had more deciduous trees and leaf litter on our property! We’d be making piles of supreme leaf mold, that’s for sure. (Leaf mold is just another name for fully composted shredded leaves). It is best to use shredded leaves for mulch. Whole leaves clump together and can create a mat that blocks the passage of water or air to the soil. Easily shred leaves by simply passing over them with a lawn mower. Then, the small pieces are all collected in the bag – ready for mulching with.
- Chances are, you can collect leaf litter for free!
- Leaves are light and easy to work with.
- Shredded leaves readily decay, providing nutrients and fresh biomass to the soil.
- Dense leaf layers do an excellent job at smothering weeds.
- Supply may only be seasonal, unless you can figure out a way to store your collected leaves.
- Leaf mulch needs to be replenished each season.
- Leaf piles tend to harbor pests like snails, slugs and pillbugs.
- Insufficiently shredded leaves (or very thick layers of shredded leaf mulch) may mat and block air or water exchange to the soil.
6) Cardboard, Newspaper, or Burlap
Natural cardboard (undyed, unwaxed) can be used as ‘sheet mulch’ either on its own, or with heavier organic materials like wood chips on top to hold it down. Simply rip off your shipping labels and tape, and put those delivery or moving boxes to good use! Burlap fabric or several layers of newspaper can also be applied in the same manner.
- Cardboard is easily accessible, inexpensive or even free.
- Repurposing cardboard from shipped items into use as mulch is a superior form of recycling: upcycling!
- Sheet mulching is incredibly effective at holding moisture in the soil and also smothering weeds – perfect for large open spaces, in pathways, around trees, and under new raised beds.
- Burlap sacks (such as coffee sacks) or rolls of burlap fabric make great long-lasting sheet mulch. You could also add a layer of newspaper below burlap for added protection.
- Like other organic types of mulch, natural paper products decompose and release nutrients to the soil over time. Burlap will take longer to decompose than paper, but can also be rolled up and reused as needed.
- Cardboard is usually too large, thick and awkward to use amongst full vegetable or flower beds, with the exception of their pathway areas.
- Avoid shiny, colorful newspaper inserts. Those will not degrade easily and may contain toxic dyes.
- In my experience, woven burlap sacks occasionally contain a combination of natural fibers (jute) along with synthetic plastic-like fibers for added durability. If your intent is to allow the burlap fabric to decompose on the soil surface, steer clear of any that aren’t made from 100% biodegradable materials.
7) Other Plant Materials
A plethora of other organic mulch materials are out there, if you simply take a look around! Pine needles, dry grass clippings, sawdust, and living (or cut) cover crops are all popular natural mulch options as well. In Australia, shredded cane sugar mulch is readily available and commonly used much like straw – but without the risk of seeds. We love to collect and use miscellaneous nutrient-rich plants like yarrow, borage, comfrey, and fava bean leaves and stalks from our garden. Like leaves, it is best to cut those into smaller pieces before spreading them over the soil surface.
- With a little creativity, you can likely find many types of natural mulch materials in your yard – for free! Hint: they’re the same types of things you’d collect to add to your compost pile or worm bin; especially those that would fall into the compost “browns” or carbon category.
- At the risk of sounding like a broken record, here I go: All of these natural materials will feed the soil as they decompose, simultaneously increasing nutrient density along with the activity of worms and beneficial microorganisms.
- Avoid using grass clippings if the lawn has been treated with insecticides or herbicides. I personally would not want any synthetic lawn fertilizer residue going into my edible garden either.
- Some plants may readily self-seed and later sprout in your garden, which can be a nuisance. For instance, chopped borage leaves make stellar green mulch, but I suggest avoiding getting their flowers or seeds in the mix! You’ll have borage everywhere.
- Overly thick layers of plant matter can form a solid mat across the soil and be counterproductive, smothering soil (and the soil food web) instead of gently protecting it. The general rule of thumb is to spread mulch in a 2 to 4 inch layer. Yet, err on the lighter side to test the performance of any new-to-you material.
8) Plastic Sheeting or Landscape Fabric
Examples of man-made, inorganic mulch products include black plastic sheeting and geotextile landscape fabric, also sometimes referred to as “weed cloth”. They can be used straight on the soil surface alone, or as a liner below other materials – such as under gravel or bark in pathways. It is usually pinned down in place with landscaping staples. While it is true that these types of mulch products are synthetic and don’t offer the same soil-enriching benefits as organic mulch does, they do have notable benefits.
- Black plastic sheeting and landscape fabric can be incredibly effective at suppressing weeds and reducing evaporation, which saves both effort and water. In fact, they’re often more successful at blocking weeds that other types of mulch.
- The application of black plastic or similar materials on the soil surface as sheet mulch warms the soil and radiates heat to plants overnight, which heat-loving vegetables like tomatoes, peppers, and eggplants love.
- This ability to warm the soil also helps those plants get a boost in the early spring, or survive longer into the early fall. (Though all mulch provides insulation for soil and plant roots).
- Landscaping plastic or fabrics don’t add nutrients or organic matter to the soil like other mulch does, though they can still help with soil water retention, erosion, runoff, and insulation.
- Some plastic sheet materials aren’t very permeable, and therefore can cause pooling or drainage issues. Seek out products that are breathable and permeable to water.
- Synthetic groundcover products are not created equal, by any stretch of the imagination! There is some awful thin stuff that readily tears to shreds, thwarting its purpose while also creating a mess and waste. However, there are also high-quality durable materials available that will last for years and years – longer than organic mulch.
I hope that this exploration on various types of garden mulch was informative, interesting, and helps you narrow down your selection. No matter what type of mulch you choose, remember that any mulch is better than none! Barren exposed soil is prone to runoff, erosion, and quick evaporation. Mulch keeps soil protected and healthy – along with your plants!
However, don’t be tempted to go overboard. As a best practice, apply two to four inches of mulch on top of the soil surface. Too deep of a mulch layer can lead to excessive moisture and root rot. Also avoid piling mulch directly up against tree trunks or the stems of tender plants, which can make them susceptible to rot or pest problems.
Thank you so much for tuning in! Please feel free to ask questions in the comments below, and spread the mulch love by sharing this post.
Don’t miss these related articles:
- Mulching 101: When, Why & How to Mulch Your Garden
- What is No Till Gardening? The Benefits Explained
- Composting 101: What, Why & How to Compost at Home (6 Ways!)
- How to Amend and Fertilize Garden Soil Between Seasons
- How to Kill or Remove Grass, and Grow Food Not Lawns!