Mulching, what you need to know

Lee ArmilleiField Notes

Spring is the time of year for property cleanups; weeding, pruning,and mulching beds. When it comes to mulching, there is more to know than you might initially think. Follow some advice from the experts to select the right type, do it correctly, and spend your money wisely.

Described below are some of the benefits of mulch, types of mulch, problems caused by improper mulching, and finally notes on how to mulch properly.

Benefits of mulch

Weed suppression

When applied to a depth of 2-4 inches, mulch acts as a weed barrier. Although weed seeds can blow in and germinate on top of mulch, weeds in the soil layer are less likely to germinate due to lack of sunlight. Additionally, if weed seeds do germinate, the plants tend to be easier to remove in a mulched bed.

Moisture regulation:

Mulch allows water to soak into the soil and protects it from evaporating. A layer of mulch reduces the amount of water needed and saves time by eliminating the need for repeated applications. Just make sure to water thoroughly so that the water reaches the entire root-ball of your plants.

Improved soil

Natural, organic mulches break down and provide beneficial nutrients to the soil. Organic matter also improves soil texture, moisture retention, and a slow release of nutrients.

Erosion control

Mulch acts as a protective cover and helps prevent soil erosion. Sediment from eroded soil is a major contributor to water pollution. Plus, the top layer of soil is usually rich in organic matter, so there’s no sense in letting that wash away. Therefore, bare soil should always be covered, and mulch is an excellent way to do this.

Plant protection

I see it all too often- trees in the middle of lawn with gashes in the trunk. I also see surface roots in lawns that have been repeatedly run over by mowers and aeration machines. Mechanical damage to trees creates wounds that invite infection, weakening and possibly killing the tree. A layer of mulch around your plants provides an excellent physical barrier between the plants and maintenance equipment.

Types of mulch

Leaf mulch

This is the GreenWeaver favorite and great choice for sustainable gardens! Leaf mulch is the partially decomposed leaves collected in autumn. It’s often available through townships and boroughs that do fall leaf collection, and then sold back to the community. You can also manage your own leaves or simply spread fall leaves through the garden in fall. Furthermore, it replicates the natural forest process of decomposition and adds all of the benefits to a garden listed above.

Shredded hardwood mulch

Shredded hardwood is readily available, reasonably priced, spreads and smooths easily, and breaks down over a couple years. Its functional, tasteful, and an all around good choice for the garden. At GreenWeaver, we only use natural brown mulch.

In addition to natural brown mulch, there are now other color choices. Black mulch? Red mulch? How about purple or green? (Yes, it unfortunately exists.) More expensive than natural brown mulch, dyed mulch is marketed as better because it has dye that keeps it looking fresh longer. The dye is actually the most annoying part of the mulch. It’s messy to apply; it stains sidewalks; and the dye can even be tracked inside on shoes. In the horticultural hot-bed in which we live, there’s a reason display gardens never use dyed mulch.

Pine straw

Pine straw is commonly used in the south, but less so in the mid-Atlantic. Personally, I like the style and texture. It is light and very easy to apply and, surprisingly, doesn’t blow away. It is particularly good around acid-loving plants since pine straw has a low pH. My only real issue with pine needle mulch is that it is usually transported from the Carolinas. Mulch is a personal choice for the garden, but I honestly think pine mulch quite beautiful.

Licorice root mulch

Licorice root mulch is about 2-3 times more expensive than shredded hardwood. The reason why people like it is that licorice root is known to have anti-fungal properties which can help prevent artillery fungus. Nothing is a sure bet though, so just be aware. When the licorice roots are shredded, there tends to be a lot of curly pieces that lock together, but during application may leave the surface lumpier than shredded hardwood. I was concerned about the carbon footprint of licorice root mulch, but it’s a by-product of the licorice industry, which makes me feel a little more at ease. I’m not sure where it is being shipped from, but there are manufacturers as close as Camden, New Jersey.

Problems caused by improper mulching

Mulch is beneficial in moderation, but can cause many problems when used incorrectly.

Improper mulching
“Mulch volcanoes” are a result of improper mulching. Excess mulch invites disease and these trees will likely die prematurely.

It may seem obvious that plant roots prefer to be underground where it is moist. It follows that when you expose roots to sun and lack of moisture, the plant suffers. Similarly, plant stems and trunks prefer to be above ground where they can dry quickly and receive sunlight.  When excess mulch is piled around the crown of a perennial or the trunk of a tree, that above-ground part stays moist for excessive periods.

Excess moisture, where it is not warranted, can cause a number of problems including disease, rot, and adventitious root growth (roots that grow from confused plant cells).

*Note on Weed Barrier Fabrics- Fabrics are inferior to natural mulch because they prevent the organic matter in mulch from breaking down into the soil. Additionally, they are ineffective because weed seeds settle on top of the fabric and germinate. Finally, weed barriers are costly. For these reasons, GreenWeaver never recommends using weed barriers in the landscape.

Proper mulching technique

  • Define the mulch area and cut an edge to the bed if desired. Please be careful not to cut roots to desirable plants.
  • Spread 2-4 inches of mulch through the open areas.
  • Avoid the base of perennials, shrubs, and trees.
  • Remove any mulch that ended up on top of plants.
  • Smooth out any bumps and lumps. Get on your hands and knees for best results. Or, use the back of a rake for larger areas.
  • Maintain mulch annually. Do not allow more than four inches of mulch to accumulate. If the goal is aesthetics and there is already enough mulch, either remove the old mulch and compost it, or sprinkle a very light decorative layer over the old mulch.

Now that you’re an expert, make sure any open areas in your garden get a healthy layer of mulch. And of course, contact GreenWeaver if you need help.