Mulch has a number of benefits for the garden. However, you need the right mulch to get the most benefits from it. Here is a guide to when and how to use hardwood mulch.
What Is Hardwood Mulch?
Hardwood mulch is the ground-up bark and wood of hardwood trees. It is often a by-product of work on utility lines or in the lumber industry. The mulch contains many species of wood. The individual pieces vary in size. Some hardwood mulch is shredded instead of or after being chipped. To achieve a smaller particle size, some hardwood mulch is shredded multiple times.
Pros and Cons of Hardwood Mulch
Here are some specific pros and cons when using hardwood mulch.
Hardwood mulch is readily available. It is sold in big box stores and nurseries. In addition, some municipalities offer it to people who live in that area, and all you have to do is shovel it into your vehicle. Hardwood mulch is available in bulk from soil and mulch vendors in most areas.
Hardwood mulch is the least expensive type of mulch. As mentioned, in many cases, it is available for free from city utility departments. A bag of hardwood mulch is usually under $5.00 when picked up. It may be more expensive if delivered.
Regulates Soil Temperature
Like all mulches, hardwood mulch helps keep the soil warmer in the winter and cooler in the summer. In the spring, mulch may delay the soil warming up slightly, but this can be fixed by moving the mulch aside until the soil warms up, and then putting the mulch back.
Regulates Soil Moisture
By covering the soil, hardwood mulch helps regulate soil moisture. The wind doesn’t blow across the soil, drawing moisture out of it. By covering the soil, mulch protects it from the sun, slowing evaporation.
Because mulch covers the soil and dissipates the rain falling on it, mulch helps retard erosion. While it won’t stop gullies from forming in a flood, normal rainfall is much less likely to wash away soil. Wind can’t blow soil away because it is covered by mulch.
A thick layer of hardwood mulch retards the growth of weeds. At the recommended depth of three inches of mulch, something about the wood chips keeps weed seeds from germinating. If they do germinate, the weeds die before breaking out of the mulch. Scientists are not sure exactly why this occurs, but lack of sunlight, a local like of nitrogen, and possible chemical compounds produced by the wood chips are some possibilities. Since weeds steal water, nutrients, and sunlight from your plants, keeping them under control is very important.
Adds Organic Matter to the Soil
A layer of mulch three inches thick decomposes about an inch of mulch a year. This adds organic matter to the soil, which improves soil structure and feeds the soil microorganisms that help plants grow.
Prevents Soil Splashing
Many diseases live in the soil. When the soil splashes up onto wet leaves, the disease is able to grow and infect the plant. A layer of hardwood mulch prevents the soil from splashing up on the plants. This reduces the incidence of soil-borne diseases.
Protects Tree Trunks
Wire and string edging tools can cut the bark off of trees and shrubs and leave injuries. Sometimes those injuries are severe enough to kill the tree. Other times, they allow entry into the tree tissue for insects and diseases. Even if the injuries do not kill the tree, they are unsightly. A layer of mulch on the ground around the tree keeps grass from growing, eliminating the need to edge around the tree. This protects the tree trunk from those kinds of injuries.
Keeps Fruits and Vegetables Off Soil
Using hardwood mulch around fruits and vegetables keeps the produce from touching the soil. This prevents belly rot and other rot caused by soil-borne diseases. A layer of mulch also protects the fruits and vegetables from many insects that live in the dirt. Produce is also cleaner when harvested, reducing processing time.
Reduces Soil Compaction
Covering soil with mulch reduces soil compaction. You have to spend less time standing on the soil weeding. The organic matter mulch adds to the soil also breaks the soil up and leaves it less compacted. Compacted soil resists water and air infiltration, causing problems for the roots that live in it.
May Contain Pesticide Residue
If you source your hardwood mulch from municipal mulch piles, some chips may have pesticide residue or diseases on them. However, research has shown that this is not a significant factor in damaging plants the mulch is used around. There were some pesticides that were used on lawns that, when mixed into mulch or compost and spread around trees, caused the trees to die. These pesticides were withdrawn from the market and are no longer used.
May Deplete Nitrogen
The soil microbes that digest mulch and help it decompose use nitrogen during that process. When spreading mulch over a new area, the nitrogen in the top part of the soil may be temporarily depleted by the soil microbes. This does not appear to be a long-lasting depletion, since the mulch itself has nitrogen in it that becomes available as it decomposes. However, when first mulching a new area, I sprinkle some blood meal around on the soil before I add the mulch. This adds enough nitrogen to offset any temporary depletion.
If you get hardwood mulch from a municipal utility, it has not been heat treated and may contain weed seeds. However, this is usually not a major problem. I would confidently use municipal mulch without worrying about excess weeds.
Termites and Other Insects
Hardwood mulch will not cause termites, particularly if the mulch is bagged. Bagged mulch is usually heat-treated to kill weed seeds and insects in it. Hardwood mulch can provide a bridge from the soil to your house for termites. Leave a six-to-eight-inch gap between your house and any mulch you spread.
Applying Hardwood Mulch to the Garden: When Do I Use It and When Do I Not Use It?
Hardwood mulch is appropriate for any place mulch is called for. I use it around trees and shrubs, in landscape beds, and in my vegetable garden. I also use coarser hardwood mulch for garden paths.
What Is The Best Time To Apply Hardwood Mulch?
In the spring, I add an inch of hardwood mulch on top of my existing hardwood mulch to replace the mulch that decomposed over the last year. This not only replenishes the mulch, but it also makes my landscape beds and the areas around the trees and shrubs look fresh and bright.
I place mulch around transplants as soon as I plant them, as long as they are at least four inches tall. If they are shorter than that, I start with a small amount of mulch on the ground. As the plant grows, I gradually add mulch until I have a three-inch layer around the plant.
When planting seeds, I remove any mulch from the ground and then plant the seeds. I wait until the seedlings are four inches tall to add mulch around them.
How To Apply Hardwood Mulch To The Garden
Never let the mulch touch the trunk of a tree or shrub or the stem of a plant. Always leave a three-inch gap between the tree trunk and the mulch and an inch gap between the stem of a plant and the mulch. If the mulch touches the plant, it will cause a spot of rot that may be fatal. After applying hardwood mulch, always water enough to soak the mulch. Otherwise, it will wick the soil moisture out of the ground and tie it up so your plant can’t get it. Hardwood mulch is safe for use around pets.
I use hardwood mulch around my seedlings in the vegetable garden. I spread it around the stem, so the mulch stretches from one seedling to the next. In an area where I am planting vines, like pumpkin or watermelon patches, I spread the mulch around the area where the vines will grow before I plant my seeds. I do not put the mulch where I plant my seeds, but when the seedlings are four inches tall, I spread it around them. This means that when the fruit, like the watermelon, grows, it is on a bed of mulch instead of on the soil. I don’t have as many weeds or diseases using hardwood mulch this way.
I use hardwood mulch in my flower beds anywhere I have transplanted plants. I wait to spread it where I plant seeds until the seedlings grow. Hardwood mulch in flower beds also hides my irrigation hoses so my drip irrigation does not look unsightly. Trickling the water to the roots under the mulch keeps so much water from evaporating, especially in the hot summer months.
I would use hardwood mulch around my fruit trees if I only had one or two. Make a donut around the tree trunk, with mulch from three inches from the tree trunk to the edge of the drip line.
I use living mulch like white clover in my orchard. It is cheaper, and the bees love it. In addition, the living mulch fixes nitrogen.
I go ahead and use hardwood mulch around all my berries, even the acid-loving ones like blueberries and strawberries. The hardwood mulch doesn’t really change the pH of the soil, so I use fertilizer for acid-loving plants around my blueberries and strawberries to provide the acidity they need. Blackberries, which prefer alkaline soil, do very well with hardwood mulch around them. I spread the mulch from just around the stem to the edge of the dripline.
Ornamental Trees and Shrubs
Hardwood mulch is appropriate for any tree or shrub. Start with a three-inch layer three inches from the trunk and extending to the edge of the drip line.
I use coarse hardwood mulch on my garden paths to make a cushioned surface to walk on and keep down the weeds. It is cheaper than gravel and easier to use.
Where Do I Buy Hardwood Mulch
Hardwood mulch is readily available. You can buy bags of it from the big box stores like Home Depot, Lowe’s, and Walmart. Most nurseries have bags of it, and some have bulk piles, which are cheaper. As mentioned above, some municipalities offer hardwood mulch free if you go and pick and shovel it into your vehicle. Finally, bulk soil and mulch dealers will deliver a load for a fee. You can buy hardwood mulch online, but often the shipping is so much that it is cheaper to go pick it up locally.
Some Good Hardwood Mulch Options
I buy Timberline hardwood mulch. They offer a range of mulch types, including shredded and chipped mulch. Timberline is a company that distributes primarily in the Eastern and Midwestern United States. The mulch is made from bark and wood waste from sawmills. I like that they take a product that would otherwise be burned and make something useful out of it.
Vigoro produces premium-colored mulches using hardwood chips. They dye the mulch different colors, such as black, reddish brown, or red. I prefer natural hardwood mulch, but some people think the dyed mulch shows off their plants better. Vigoro products are only sold at Home Depot stores.
Hardwood mulch is appropriate for any application you need mulch for. I use it in my vegetable garden, around my trees and shrubs, and on my garden paths. It is widely available and fairly cheap. Sometimes you can even get it for free from municipal utilities.