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Mulching: Benefits and How Tos

What is Mulch?

Mulch is organic matter that you can lay on top of the soil to cover it up. Common types of mulches include: shredded bark, wood chips, straw, saltmarsh hay, cocoa bean hulls, composted leaves, and grass clippings. Anything that is from a natural source (not human-made like plastic), doesn't contain weed seeds and isn't too green (such as fresh grass clippings) can be used as a mulch.

When it comes to mulch, use what's cheap and readily available because it usually has to be reapplied every other year.

What is Mulch Used for?

To understand what mulch is, learn from nature. Go out to a wooded area and look on the ground. Do you see bare soil? Of course not. You see a layer of decaying organic matter, such as leaves. If it hasn't rained for awhile, you'll notice that the top of the leaf layer is dry. But, turn it over and you'll see moisture on the leaf litter and on the soil. Put your hand on the moist ground that was covered by the leaves and you'll feel that it is cool to the touch. You might also see all kinds of little critters, like earth worms and other bugs that are eating the mulch, breaking it down and making the nutrients available to the plants that are growing nearby. This is how topsoil is made. Plant material dies, falls to the ground, is broken down by organisms (from worms to bacteria) and is turned into nutrients and humus. Soil life is possible only when there is food, water and shelter. Nature provides the food and shelter each time a leaf falls onto the ground.

When soil is uncovered it becomes vulnerable to the ravages of the sun, wind and rain. Baresoil also can't provide food and shelter to all the critters that help break down organic matter and keep the soil alive. As gardeners, we want healthy soil that is teeming with life so our plants that we spend time and money on and build our passions around can thrive.

Applying mulch to our gardens mimicks how nature cares for plants in the wild. Mulch protects our soil, provides food to beneficial soil organisms and add nutrients to the soil.

Benefits of Using Mulch:

• Protects the soil from wind and rain erosion.
• Shades the soil from being baked by the sun. Hard, baked soil repels water and limits the movement of oxygen into the soil.
• Retains soil moisture.
• Keeps the soil temperature more constant than if it was exposed to the air; thus, protecting it from extreme heat and cold.
• Provides food and shelter to beneficial soil organisms such as earthworms.
• Breaks down into soil-building humus and nutrients with the help of the soil organisms it provides an environment for.
• Prevents weeds from taking over. And weeds that do happen to grow through the mulch are easily pulled out. Weeds are the earth's bandaids, who quickly move in to cover up any bare soil. Don't encourage them by providing them with the right conditions. Cover up that dirt!
• Prevents soil from splashing onto plants. Plants with mud splashed on them look bad. And, the soil can often carry spores and diseases that then get splashed right onto your plants. Not a good thing.

How Do I Use Mulch?

To a new garden, we apply a 3- to 4-inch layer of shredded bark on top of the soil. We are lucky to have a sawmill two miles from our nursery and can get large quantities of shredded bark. Remember the "cheap and readily available" motto when it comes to mulch.

To existing gardens, we apply a new 1- or 2-inch layer of shredded bark each spring right on top of the old mulch. This does two things:

1. Replenishes the mulch that decomposed the previous year.
2. Covers up dead leaves from our roses that may have had disease spores on them, such as blackspot or powdery mildew. Burying the spores prevents them from being released to the air.

A fresh layer of mulch each spring also makes the gardens look nice.

Yeah, but...!

Q: Yeah, but I heard that mulch will cause your plants to turn yellow because it ties up the nitrogen in the soil.

A: This is true only if mulch is incorporated into soil that is already low in organic matter and nutrients. Mulch that is placed on top of the soil rarely, if ever, causes nitrogen deficiency because the nitrogen used to break it down is quickly replaced through the decomposition process. Before a mulch is applied to bare soil, the soil should be ready for plants. That means it should have lots of organic matter, such as manure or compost already incorporated into it. And it should have a high level of nutrients. These can be added by incorporating into the soil a slow-release, all purpose, natural or organic granular fertilizer. The pH should also be at a neutral level: from 6.5 to 7.0.

Q: Yeah, but I heard that mulch makes a good home for overwintering insect pests.

A: O.K., it just might, but it also makes a good home for the bugs that eat the pest insects. In the neverending struggle of prey and predator in the insect world, you'll quickly see that a balance will be struck in a well-mulched garden between good bug and bad bug. As you move your mulch around to plant a new rose, you might notice a few predatory beetles dashing for cover. These guys are voracious! They seek out all kinds of nasties, such as grubs, slugs and whatnots and eat them for lunch. Much more happens in this battle underneath the mulch than we may ever realize or appreciate (or want to know about). If you have an insect pest problem, there are lots of ways to control them that have a minimal impact on the fragile balance found in a healthy garden. You can find out more about insects and natural controls on our bugs page. You'll need to decide for yourself what you're willing to tolerate, and weigh the benefits of mulching against the downside of maybe having a few bad bugs show up in your garden now and then.

Q: Yeah, but I don't have a sawmill two miles from my house and I don't know where to get any mulch.

Check with your local hardware store, home and garden store, or nurseries. All of these types of stores carry mulches of some kind --usually wood chips or shredded bark -- and sell them in bags or in bulk. The bagged mulch is usually pretty cheap, from $1 to $2 per bag. Lots of municipalities also have leaf composting operations. They usually give the compost away to local residents, or charge a minimal fee. Power companies are always trimming tree branches and need to get rid of all the ground up bark. They'll usually deliver all you want for free. If your neighbors have lots of leaves bagged up every fall, you can get those for free (along with a few curious looks) and make your own compost to use as a mulch.

As you can see, I have an answer for just about every "yeah, buts" when it comes to mulch. I'm a firm, staunch believer in mulches. Ever since I read Ruth Stout's "No Work Garden" book back in the '70s, which very convincingly advocates the use of mulch, I've never left any soil uncovered. Bare soil just isn't natural. Remember the dust bowl of the '30s? The hardworking, well-meaning farmers tilled up all the prairies and exposed vast amounts of fragile soil to the wind and sun and the wind won. The same thing, albeit on a smaller scale, can happen in your backyard.

If you want to weed all the time, watch your soil wash away each time it rains, take more from your soil than you put back, get hit in the eye with dust during a dry windy day, subject your little plants to drowning in mud after a heavy rain, and treat your soil like dirt, then don't mulch.

But, if you want to have a healthy garden and leave your soil better than when you found it, try mulching.