The word “mulch” brings lots of thoughts to a gardener’s mind. Wheelbarrows, shovels, dust-covered arms, backaches, and calluses are just a few of the things the word conjures in my mind. Few people think about a ripe, red tomato, a perfect rose blossom, or a gorgeous hydrangea when they think about mulch. But, truth be told, without mulch, all of those beautiful things are far harder to come by. Despite its practical purpose and humble appearance — not to mention how much work it is to spread — mulch is absolutely essential to a healthy, productive garden. Let’s get digging into mulches and learn the whys and hows of this important gardening task.
What is mulch anyway?
Mulch is any material placed on top of the soil to suppress weeds, conserve soil moisture, add organic matter, and provide an attractive backdrop for plantings. Mulch can also reduce erosion, improve the soil’s structure and fertility as it breaks down, and stabilize soil temperature fluctuations. All of these benefits are why mulching is a key strategy in climate change gardening. As you can see, there are so many good reasons to make mulch a part of your garden.
Digging into mulches
But, not all mulches are created equal. While any material placed on top of the soil is technically considered a mulch, not all mulching products provide the same benefits. Your choice of mulching materials impacts the garden in many ways, and different garden areas call for digging into mulches of different kinds.
Garden areas can be broken down into three types:
• Intensively grown flower and vegetable beds
• Less-intensively planted areas, like tree and shrub beds
• Walkways and paths
Each of these three areas calls for a different mulching material.
• In intensively grown flower and vegetable beds, you’re going to want a mulch that decomposes quickly to add nutrients and organic matter to the areas where these fast-growing annuals, vegetables, and perennials are growing. This type of mulch typically has finer-sized particles and is broken down by soil microbes very rapidly.
• In less-intensively planted tree and shrub beds, stick with a mulch that is slower to break down. These products last longer, are less expensive, and have a larger particle size.
• For walkways and paths, choose a mulch that’s very long lived. It may even be something that won’t break down at all, such as rocks or gravel. Pathways need to be mulched less frequently than areas where plants are growing, so you’ll want the mulch to last for as long as possible.
Digging into mulches also means considering the preferences of your plants when deciding which type of mulch to use in your garden. For example, blueberries, azaleas, evergreens, and other acid-loving plants love to be mulched with pine needles that, over time, breakdown and help acidify the soil. Most other vegetable and flower garden plants, however, prefer a soil pH around 6.5, so mulches with a more neutral pH are best for areas where these plants are growing.
Types of landscape mulch
To help you decide which mulch is best for which garden area, here are details on a few popular mulching products.
Finished compost is a useful mulch for many different reasons. It’s affordable (or free, if you make your own!) and quick to break down, making it a great choice for intensively planted flower and veggie beds. Compost adds organic matter back to the soil faster than some other mulching products. It also spreads easily since its fine particles sift down around the plants.
Straw is an excellent mulch, especially in the vegetable garden. When digging into mulches that are loose, like straw, you’ll find that they’re also better at deterring pests that lay eggs down close to the soil, such as flea beetles, squash vine borers, and root maggots. Straw is inexpensive, easy to apply, and takes a season or more to fully break down. In my own vegetable garden, I use straw to mulch the walkways and larger vegetable plants like tomatoes and peppers. It also works well beneath cucumber and melon vines where it helps keep the developing fruits off the soil.
Shredded Bark or Hardwood
Shredded bark or hardwood mulches are great around woody plant material like trees and shrubs. Many landscape suppliers have single-, double-, and even triple-shredded wood products, depending on how quickly you’d like it to break down. While single-shredded lasts longer, it’s coarser in appearance than the finely graded triple-shredded mulches. Avoid dyed bark mulches, if possible, as well as cheap “gas station” mulch that could be made from construction debris and might contain contaminants.
A popular mulch in the Southern U.S., pine straw is made from naturally shed pine needles from several long-needled pine species. Because the needles interlock and stay in place, pine straw is an excellent mulching choice for hillsides and other erosion-prone sites, as well as for flat ground. As the needles are fairly acidic, when the pine straw decomposes it acidifies the soil slightly, making this an excellent mulch for acid-loving plants like blueberries, rhododendrons, camellias, ferns, magnolias, and evergreens.
Leaf Mold or Leaf Compost
This type of compost is comprised of a single ingredient: leaves. It can be made commercially from municipally collected leaves or at home from leaves collected on your own property each autumn. Leaf compost is friable, loose-textured, and lacks weed seeds. It breaks down quickly to release organic matter and is a great choice for flower beds and vegetable gardens.
When digging into mulches and discussing different kinds, one can’t forget about the freebies! Grass clippings collected from organic lawns are an excellent (and free!) mulch, just don’t use clippings from a lawn that was treated with broadleaf weed killers or you could harm your plants. Grass clippings decompose very rapidly, but because of their high nitrogen content and fresh state, they can burn young plants if over applied. Two inches of fresh grass clippings added every week or two are plenty. They are a great mulch when applied between crop rows in the vegetable garden.
Mushroom compost (also called mushroom manure or mushroom soil) is a popular mulch in some parts of the country. Essentially, it’s the by-product of the mushroom farming industry. Mushroom compost starts as a combination of decomposed organic materials like manures, straw, peat moss, and shredded corncobs. Though it’s originally used to grow mushrooms, the spent product remains high in organic matter and some plant nutrients. It’s inexpensive and readily available, and can be used on flower and vegetable beds. However, mushroom compost is not a good choice for shrub beds, especially those housing salt-sensitive evergreens. Mushroom compost is fairly high in soluble salts and, while mixing it into the soil does dilute them, applying a heavy mulching of mushroom compost can cause salt burn on certain evergreens.
There are, of course, other types of landscape mulch, but these are among the most popular.
How to mulch garden beds
After you’ve selected the best mulch for a particular garden area, it’s time to literally get digging into mulches and learn how to spread them. Regardless of what types of landscape mulch you select, proper application plays a key role in ensuring the health of your garden plants.
Here are some excellent mulching tips to keep in mind:
• Be careful not to smother plants under too much mulch. Apply two inches of compost or other fine mulches. For loose mulches like straw or pine straw, keep it under four inches. For coarse-textured mulches, like shredded hardwood or bark mulch, three to four inches is perfect.
• Mulch should never contact the stems or trunks of plants. Doing so makes the plant more susceptible to disease and insect damage. Never pile mulch against the stems and bark of shrubs and trees. A good rule of thumb is to keep any mulch at least three to four inches away from the base of the plant.
• The timing of mulch applications matters as well. Don’t apply mulch too early in the spring, while the ground is still saturated, or the soil may stay waterlogged for a long time. Alternatively, don’t mulch when the soil is too dry. Wait until a day or two after a good soaking rain in mid-spring to apply your mulch.
• Apply mulch before weeds become problematic. Throwing mulch over existing weeds won’t necessarily smother them, and you may find them popping up through the mulch a few days later. Weed beds thoroughly before laying down mulch.
As you can see, digging into mulches means choosing the right product for each area and applying it properly. Though mulching isn’t a glamorous job, it is a very important one. With a good layer of mulch in place, summer maintenance chores, such as weeding and watering, are greatly reduced and your garden beds look fresh and lovely.
Tell us about your favorite mulching product in the comment section below.
John Sonnenday says
Around trees and shrubs, I much prefer pine bark nuggets because they las a very long time. But they have become hard to find.
Christopher Mousseau says
I’m also a huge fan of mulching so thanks for this article! A couple points people may want to consider – grass clippings as a mulch may not be a great idea if any of the grass you’ve cut has produced seeds. In my experience there’s nothing more onerous than trying to remove grass from a flower bed!
Also – the notion that pine needles help acidify soil is a myth. Studies have shown that green needles are just slightly acidic, by the time they turn brown and fall off they are barely acidic and after just a few days on the ground they are not acidic at all. (www.gardenmyths.com)
Travis Lucy says
I’m a novice gardener and mulched for the first time with grass clippings this year. I don’t remember how thick the layer was, but I needed to pull grass from my vegetable beds a few times. At least my grass problem was less severe than my weed problem would have been.
Does this mean I should apply a thicker layer of grass next year?
A lot of my vegetable garden is in the shade of generation-old trees. Should I still apply 2 inches of mulch for optimal results?
Jessica Walliser says
Hi Travis – The grass popping up in your garden is a sign that perhaps your grass had gone to seed prior to cutting it. If you’re going to use grass clippings to mulch a garden, it’s best to mow a bit more regularly to ensure none of the grass plants have produced any seed that might sprout up in the mulched beds. One to two inches thick is plenty for a layer of grass clippings; any thicker and it could prevent moisture and air from moving in and out of the soil.
Dave C says
For s few years now I’ve collected leaves from my property in the fall, shredded them, and composted them in wire bins or fight on top of my raised beds. In the springboard move the partially composted leaves aside to plant. Sometimes I need to add more partway through the summer. By the next fall those leaves have all Ben incorporated into the soil, and I start over. I’m experimenting with no-till gardening so I’ll let you know how this works out.
Pine needles are only acidic when green, once they have turned brown they will not change the ph, that is a myth. You don’t mention arborist wood chips which are the best of the wood mulches and usually free.
I have tilled my garden I was gonna put mushroom compost on the top before plantingis
Jessica Walliser says
Mushroom compost would be okay as a mulch, but I would only use it every few years since it’s pH is fairly high and with repeated additions it can alter the pH of the soil. It doesn’t contain a lot of nutrients, but it does contain plenty of organic matter.
Rachel Williams says
It’s soooo important to know which state the Gardner lives in. Example:I’m in Coastal La.;too much rain. “Splash up”
spreads fungus; mulch is a “must”. For me CHOPPED pine straw!Shades roots, no splash up,allows air to circulate, holds its color, prevents erosion,doesn’t pack. Grass clippings, mushroom compost rots
us out. Also, seems to last indefinitely.
Rachel Williams says
How can I contact you about your potting
Soil recipe before I put it all together.
Nervous about drainage/pete to peralite.
I’m in Louisiana/you’re in Canada. Will my plants “drown”?
Jessica Walliser says
I’m in Pennsylvania. The perlite helps add drainage so your plants will definitely not drown. 🙂
Sue Gilmore says
I’m big on mulching too. In our kitchen garden, I mostly use our grass clippings as we have about an acre of lawn and we are pesticide free. In the fall, we add crumbled, dried leaves; it’s helped a lot in improving the tilth of our soil. Lots of clay in this area.