So you’re online or at the home store looking at the myriad of mulch options, and you see hardwood mulch. What is it? Does it perform better than other mulches? Is it the best choice?
The answers to those questions come down to the details of your garden or landscape needs.
In this article, we’ll look at what hardwood mulch is and the pros and cons of using it. We’ll also take a closer look at the issue of using fresh hardwood chips.
What Is Hardwood Mulch Made From?
Generally, speaking, trees fall into two main classes: hardwood and softwood.
As the name suggests, hardwoods tend to be slightly denser and sturdier than softwoods. However, according to HowStuffWorks.com, there are also several other differences between the two:
- Hardwood tree species are usually deciduous. This term means that hardwoods lose their leaves on a yearly cycle. Softwoods are typically conifers, or evergreens.
- Hardwoods form encapsulated seeds, like fruit, nuts or acorns. Softwood trees typically produced unprotected seeds in the form of pinecones.
- Most hardwood trees tend to grow at a slower pace than softwood trees.
Hardwood mulch comes from the bark and inner wood fiber layers of hardwood trees.
North America supports numerous species of hardwood trees. These examples are just a fraction.
Although you can buy 100% cedar and 100% cypress mulch, most mulches termed “hardwood” are a blend of various tree species.
Some brands even offer organic options, like this one from Organic Mechanics.
Benefits Of Hardwood Mulch
So now you know what hardwood mulch is. But what are the reasons why you might want to use it?
Let’s take a look at the benefits this mulch material has to offer.
As an organic material, hardwood mulch provides vital nutrients that your plants need to thrive.
Shredded bark is the most common form of hardwood mulch. As opposed to actual wood fibers, the bark contains a higher nutrient density that enriches your soil and feeds plants.
Forms a Strong, Protective Layer
With time and water exposure, hardwood mulch tends to compact more than some other mulch materials.
Thanks to this quality, hardwood mulch is great for:
- Deterring weeds
- Preventing soil erosion
- Retaining moisture
- Insulating roots from temperature fluctuations
- Resists washing or blowing away
Because the natural fibers tend to form such a strong network, hardwood mulch can be an excellent choice for slopes or water-prone areas.
Some Varieties are Very Long-Lasting
While rapid composting may be a priority for some gardeners, you may be looking for a mulch that you won’t have to replace often.
Especially if you choose a chipped version, oak tends to be the best hardwood mulch in terms of longevity. In fact, you may be able to go several years between re-applications.
Much hardwood mulch comes from the tree’s bark. As trees are harvested for lumber, the bark is often the first by-product.
Converting bark into mulch recycles the leftovers instead of sending them to the landfill.
Drawbacks Of Hardwood Mulch
Even though hardwood mulch brings plenty of advantages, there are some drawbacks to keep in mind.
May Block Water and Airflow
The fact that hardwood bark mulch compacts brings some great benefits, but it can also have a dark side.
Hardwood mulch fibers aren’t naturally absorbent. As a result, freshly applied mulch provides excellent drainage for water to reach your plants’ roots.
As the mulch compacts over time, though, water may start to run off the mulch surface rather than reaching the soil.
You may also run into a problem with your plant roots getting proper airflow. While keeping moisture in the soil is usually a good thing, permanently damp soil could lead to root rot.
This could be especially troublesome for plants who prefer drier soil, like blueberries or succulents.
One way to prevent to serious compaction issues (especially around vulnerable plants) is to stir up your hardwood mulch regularly.
May Attract Termites
If you live in a termite-prone area, adding additional wood to your property in the form of mulch may increase your chances of a terminate infestation.
If you already have a termite problem, look for a different mulch material. If you’re drawn to the appearance of wood mulch, both cedar and cypress have natural insect-repelling qualities.
The Dangers of Fresh Hardwood Chips
Have you recently chipped up brush or trees on your property, leaving you with fresh wood chips sitting around? Does your local municipal department offer free wood chips from tree-trimming projects?
If so, you might be thinking about using these chips as garden mulch. After all, why not rid yourself of leftover chips or spread a layer of free mulch?
Not so fast.
Fresh hardwood chips are not the same as mulch that you can purchase from a nursery or big box store. Store-bought mulch has been aged for at least one year, so the decomposition process has already begun.
Let’s take a look at a couple of issues you may run into with fresh hardwood chips.
Risk for Spreading Plant Disease
If you use freshly chipped mulch made from diseased trees, you run the risk of introducing the pathogen to your existing plants.
Fortunately, this drawback appears to be a rare occurrence that only happens in certain circumstances. Healthy trees probably won’t have a problem. On the other hand, trees that have bark wounds or other risk factors for disease seem to fare the worst.
The aging process neutralizes most plant pathogens, so purchased mulch should keep delicate trees safe.
Key Takeaway: The risk for fresh wood chips to spread disease is likely low. But to be safe, purchase aged mulch to use around vulnerable trees.
Fresh wood consumes a great deal of nitrogen as it decomposes, and the soil is the closest nitrogen source available. As fresh wood leaches the nitrogen it needs, some plants can get left depleted.
Nitrogen deficiency can cause several issues.
- Yellow leaves
- Leaf drop
- Stunted growth
- Reduced harvests or blooms
There is good news here, though. According to Texas A & M AgriLife Extension, using fresh chips as a surface mulch will only deplete nitrogen at the soil’s topmost layer.
So as long as you don’t work the fresh mulch into the soil, you won’t have a tremendous amount of nitrogen depletion.
With that being said, even a small amount of nitrogen depletion is too much for certain garden plants. For example, vegetables and annual flowers have delicate root systems which require more nutrients to thrive.
On the other hand, plants and trees with established root systems probably won’t even notice a little less nitrogen.
Aged mulch has already decomposed to the point where it no longer leaches nitrogen from the surrounding environment. In fact, aged mulch releases its nitrogen stores.
Key takeaways: Feel free to spread a generous layer of fresh chips around established perennial flowers, trees and shrubs. But use another mulch material or aged hardwood chips for vegetable gardens and annual flowers.
In summary, hardwood mulch:
- Enriches your soil with nutrients
- Does a great job of protecting plants
- Makes use of lumber by-products
Particularly if you’ve struggled with mulch washing or blowing away in the past, a hardwood variety can be a great solution.
However, hardwood mulches can have some drawbacks, too. So be sure to take your local environment and specific needs of your plants into consideration.