Rust-colored wood chips may be the first place your mind goes when you think of mulch, but mulch isn’t limited to traditional landscaping materials. Mulch can be anything that is laid on top of the soil to suppress weeds and retain moisture in garden beds.
Compost, straw, leaves, grass clippings, wood chips, landscape fabric, and cardboard are seven excellent mulching options to use in your vegetable garden.
Keep reading for my top mulching recommendations for vegetable gardens, and a few tips on how and when to apply mulch for healthier plants and less work on your part!
The benefits of mulching
Mulching is a popular practice in landscape design and perennial agriculture, but it has a number of benefits in the vegetable garden, listed below.
Suppressing weed growth
The primary purpose of mulch is to control the spread of weeds in the garden. Weeds – other than making a garden look unkempt – rob vegetables of nutrients, water, and sunlight, so it’s no wonder most gardeners want them gone.
Mulch cuts back on the grower’s workload by suffocating weeds before they get unmanageable. Mulching a garden bed adds another layer to the soil, blocking any light that could get through and prohibiting weed germination and growth.
Retaining water in the soil
Mulching works another miracle in the vegetable garden by retaining water. The extra layer of material slows the evaporation of water from the soil, keeping water close to plant roots through even the hottest, driest summer days. Better water retention means that you have to water the garden less.
Insulating plant roots
The added layer of material acts as an insulating layer as well. Pieces of mulch trap air close to the surface of the soil, keeping plants warmer in winter and cooler in summer.
Slowing the spread of disease
Disease and pest-free mulches protect against and slow the spread of plant diseases. Soilborne diseases and fungal infections may be spread through backsplash, or rain and water droplets that splash from one plant’s foliage onto the soil, and then onto another plant. Mulch creates a barrier that absorbs backsplash and separates plant foliage from the soil underneath.
Building up vegetable garden beds with mulch slows natural processes, eroding the soil over time. Rain, wind, and animal activity are just a few of the ways that soil and nutrients are moved away from garden beds. Building up a layer of mulch every year or two slows this process by locking in nutrition where your vegetables need it.
Providing habitat for beneficial organisms and insects
Thick pieces of bark, straw, and compost provide shelter for pollinators, predatory insects, and soil-building organisms like earthworms. Beneficial insects that are introduced to the garden will be more apt to stay if shelter is available, and the presence of mulch will draw pollinators and predatory insects to the garden naturally.
Organic vs Inorganic mulch
Mulches can be either organic (once living) or inorganic (non-living). Pine bark, wood chips, leaves, sawdust, and grass clippings are examples of organic mulches, as these materials eventually decompose. Landscape fabric, black plastic, rubber, and gravel are considered inorganic mulches that don’t break down over time.
The best mulch for vegetable gardens
While not representative of every possible material you can use to mulch your vegetable garden, the following list contains the best mulches for raised beds, landscape borders, and walkways, as well as the best mulches for organic gardening.
It’s hard to beat compost in terms of nutritive capacity and aeration. Organic compost actually does triple duty in the garden–it enriches the soil with nitrogen, adds beneficial bacteria and microorganisms to the soil, and improves soil texture, aeration, and drainage.
Although bagged compost can be somewhat expensive, compost is free if you make your own at home! Composting is a great way to use food scraps while also improving the overall health of your garden.
Check out this article for some tips on what to compost, where to store your compost, how to turn a compost pile, and so much more!
Organic compost is relatively quick to break down–it needs to be applied to garden beds once a year, at minimum. Spread the compost at least two inches deep for it to be an effective mulch.
Straw is another great option for mulching vegetable gardens, especially leading up to winter, because straw traps heat immaculately well. Pieces of straw create air pockets that insulate plants from cold weather. Straw also retains moisture, keeping your garden beds from drying out too quickly.
If you choose to mulch your vegetable garden with straw, make sure that you purchase or collect straw and not hay. Though the two materials are similar – both are dried grass – hay is much more likely than straw to contain seeds. Mulching your garden with hay will only reseed the whole bed in weed seeds, so be careful!
One exception is pea hay. Pea hay is made from garden pea plants that have been harvested and dried to resemble straw. Because of its many intertangled strands, pea hay is more likely than straw to remain in place and has significantly more nutrition.
Peas are legumes, meaning that these plants absorb and store atmospheric nitrogen in their roots and release it into the soil when the plants decompose. Mulch your vegetables with pea hay and give them a boost of essential nutrients!
Straw is lightweight, so it doesn’t compact your garden beds – unfortunately, straw is so lightweight that it may blow away during heavy winds. For this reason, you’ll want to layer straw at least two inches deep for mulch.
Leaves are a great option for mulching vegetable gardens, and are easy to come by! Save your fallen leaves in autumn and compost them at home for an effective, inexpensive mulch.
The process of composting leaves is simple and takes about six months. While you might be tempted to mulch with whole or partially shredded leaves, the decomposition process is essential in this case.
Leaf mulch accomplishes another unintentional objective by creating a habitat for pollinators and other beneficial insects. Because of their seasonal availability, leaves make a great fall mulch that insulates plants against colder temps and also houses pollinators as green material becomes increasingly unavailable.
Leaves enrich the soil with organic matter and nutrients and improve the texture of the soil by reducing compaction. But be cautious when using composted leaves as mulch – some leaves, particularly black walnut, are actually toxic to many vegetables.
It’s better to use leaves from your own garden, so you know exactly what leaves you’re turning into mulch. Steer clear of any leaves that look sick, or you run the risk of introducing new diseases and pests into your vegetable garden.
4. Grass clippings
Another easy and inexpensive mulching material to use in your vegetable garden, grass clippings are quick to decompose and easy to find. Next time you mow your lawn, collect the clippings to use a mulch!
Make sure to only use dry grass clippings as mulch for your vegetable garden. Wet grass clippings can form a slimy mat that sits on top of the soil, ultimately interfering with water absorption.
It’s essential to only collect and mulch with grass clippings from a trustworthy source. Compromised grass clippings can introduce diseases and chemicals into the vegetable garden, so be sure to only use grass clippings that you know are disease and pest-free and have never been treated with any herbicides or chemicals.
One downside to using grass clippings is that it isn’t the most attractive mulch to use in the garden. As the grass clippings break down, the color will change from green to brown and may release an odor as the organic matter decomposes.
5. Wood chips
Possibly the most readily available and readily known of all mulches, wood chips are best used to mulch perennials plants and garden paths–though they can be used to mulch vegetables too.
There is a prevailing belief that wood chips, especially pine bark chips, rob the soil of nitrogen, but Linda Chalker-Scott, a Master Gardener and the Washington State University editor, dispels this myth in “Wood chip mulch: Landscape boon or bane?”
Many studies have demonstrated that woody mulch materials increase nutrient levels in soils and/or associated plant foliage. My hypothesis is that a zone of nitrogen deficiency exists at the mulch/soil interface, inhibiting weed seed germination while having no influence upon established plant roots below the soil surface.
As long as wood chips sit on top of the soil and are never tilled in, you won’t see any detrimental effects of using wood chips in your garden. For this reason, wood chips are best used in permanent beds or no-till gardens.
If you’re still wary of nutrient deficiencies caused by green wood chips, opt for wood chips that have been aged for six months or more–most gardeners agree that aged wood chips are safe for all vegetables.
Of course, quality is an important factor when acquiring wood chips to use for mulch. Although fresh wood chips from trees are totally safe for your vegetable garden, bagged and dyed wood chips may consist of pallet wood and scrap wood that could contain chemicals. Always source your wood chips locally from a source you trust.
6. Landscape fabric
For many growers, landscape fabric is the go-to mulch for its durability and ability to be customized. Landscape fabric is made of pieces of black polyester or polypropylene woven together to make a mat, and is typically sold in rolls of varying lengths sized to fit different garden beds.
Landscape fabric is excellent at suppressing weed growth because the woven mat creates a nearly impenetrable barrier for weed growth. The recycled material is also reusable and is designed to be easily put down in early spring and pulled up at the end of the growing season.
Landscape fabric can just as easily be a permanent part of the garden, especially for perennial beds and walkways. Stake landscape fabric with metal landscape staples, or weigh the material down with sandbags, cinder blocks, or any other material you have on hand.
It’s important to install an irrigation system when using landscape fabric. While the woven nature of landscape fabric allows some water to pass through, it is less permeable than organic mulches, so have an irrigation plan in place before the heat of summer sets in. Check out this article for more information on drip irrigation and how to use it.
Cardboard is another inexpensive and readily available mulching material. While not technically an organic mulch, cardboard does break down rather quickly, but is fairly effective at suppressing weeds until it decomposes. You may need to weigh cardboard down with rocks or dirt to keep it from blowing away.
Newspaper and cardboard, while excellent ways to repurpose a waste product, do have drawbacks. Some paper products are made with toxic inks and held together with tape, so steer clear of glossy newspaper and remove any tape or staples from cardboard before using it in the garden.
It’s important to wet cardboard before and after laying it as mulch, both to add weight and to kickstart the decomposition process. Dry cardboard will repel water, but wet cardboard will wick water from the surface closer to plant roots in the soil.
When to mulch vegetable gardens
It’s typically recommended to mulch vegetable gardens once a year, at the beginning of the growing season. Mulching too early can actually make plants colder, but waiting too late in the season could actually make plants hotter and more humid.
The best time to mulch vegetables is in mid to late spring, after the beds have been amended but before summer temps soar and the soil begins to dry out.
Fall is also an ideal time to mulch if you’re growing cool-season crops into the winter. Mulch will insulate plants and allow them to produce later into the season.
How to mulch vegetable gardens
Depending on the mulch used, you can mulch your garden beds before or after you plant.
Mulch annual vegetables before you plant if using plastic or fabric, but you can mulch vegetables after planting if using materials like compost and straw.
Take the time to weed your vegetable garden before you lay mulch–that last weeding will slow the regrowth of weed seeds. Not all mulches are perfect at suppressing weed growth, but organic mulches are easy to weed under–simply pick up a section of mulch, disturb the soil underneath, and return the mulch to its place.
The practice of mulching annual vegetable gardens has a number of benefits, including suppressing weed growth, retaining moisture, and insulating plants against fluctuating temperatures and contagious diseases. Any one of these mulches–or a combination of a few of them–will undoubtedly bring healthier plants and better harvests next season, so get that wheelbarrow and get to mulching!
Chalker-Scott, Linda. “Wood chip mulch: Landscape boon or bane?” WSU, Washington State University, https://s3.wp.wsu.edu/uploads/sites/403/2015/03/wood-chips.pdf. Accessed 22 November 2007.
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About the author:
When not writing content or growing flowers in her native Virginia, you can find Sarah hiking a long-distance trail deep in the woods. Follow along with Sarah’s adventures at http://sarahcolliecreative.com.