By Dr. Susan Hamilton
Mulch. You know it’s good for your landscape, but with so many choices, how do you choose which one to use? Different mulches have different attributes, so I base my selection by determining my most critical landscape need that mulch can satisfy. Any mulch will benefit your landscape by helping soil to retain moisture and by moderating soil temperatures, but different mulches will also help you in different ways.
For serious gardeners who want to see the plants in their landscape have maximum performance, an organic-rich soil is a must. The best mulch for making your landscape look neat and tidy with a well-defined design, while improving your landscape’s soil, is well-composted organic mulch such as shredded hardwood or pine bark. Composted leaves, grass clippings, peanut or rice hulls, and other green waste can also work. The more fine textured the mulch, the more quickly it will break down and be consumed into your soil, thus enriching its organic matter content and nutrient value. The coarser and larger the particle size, the slower the mulch will decompose, but the longer it will last as decorative mulch.
A variety of bark types and colors are readily available to appeal to almost everyone’s taste. By spreading the recommended 1- to 3-inch layer over your landscape beds, you will most likely find that a fine-textured mulch needs to be applied twice a year. This is not always cheap and is pretty labor intensive, but it is the best way to build your garden soil and maximize plant performance.
When I moved into a 20-year-old home with a landscape that had black plastic in all of the garden beds with super-sized pine bark chunks as the mulch, I quickly removed all the plastic and pine bark. I don’t think the previous owners ever had to mulch because the black plastic prevented the bark from making contact with the soil and decomposing. That’s not a good situation if you are a gardener like me. I’m happy to report that after six years of mulching with a finely shredded hardwood bark, I have fabulous soil!
Great soil allows me to grow just about any plant my heart desires. My soil has improved so much that last fall I made the decision to switch to a type of mulch that enhanced the reseeding of the flowering annuals and perennials I like to grow. I’m learning that the older I get, the less I want to have to plant each spring in the garden. I have been purposely planting flowering annuals and perennials that are great for seeding and volunteering in the garden each year. A coarsely-textured inorganic mulch like a mixture of sand and gravel is the best for maximizing seed germination in the spring. I rarely purchase flowering plants anymore. My chore has become thinning out the volunteers. Many make a welcomed gift to my gardening friends.
Gravel, stone, chipped brick and volcanic rock will not break down and enrich the soil habitat, but they can make an attractive mulch. And, of course, they are long lasting. Raking once a year and freshening areas with new materials is all that’s needed to keep the garden looking good.
How about pine-needle mulch? I love that it’s easy to handle and spread, and makes for a good winter-insulating mulch. Pine-needle mulch is great to use on container gardens in the winter and around pansies and other winter annuals like snapdragons, ornamental cabbage, and kale and in fall and winter veggie gardens. Somewhat slow to decompose, this mulch might give you a year of use out of it in the landscape, especially if you apply a 4-inch-thick layer. It won’t affect the pH of your soil either.
Have you heard of rubber mulch? The media has hyped the use of this recycled product. There is only one place where I’d recommend using rubber mulch: in a playground for children. Other than being recycled and a soft, cushiony and non-prickly surface cover, rubber mulch is not an environmentally friendly product. Like black plastic in the landscape, it will not decompose and enrich the soil. Rubber mulch also easily blows and washes away in heavy storms.
In the end, most of us like to use a mulch that suits our needs, both attractive and economical (that is, will last as long as possible in the landscape). No matter which mulch you choose, be sure to apply about a 3-inch layer to reap the benefits of retaining moisture and moderating soil temperatures.