Traditional gardening and landscaping often involve heavy applications of hardwood mulch around the bases of rather isolated and lonely plants. This creates a sparse, tidy space where plants are placed like furniture or ornaments.
The purpose of mulch is to help retain moisture, prevent weeds, and buffer the roots of plants from scorching sun.
Many who grew up in the 1970’s and earlier will remember when mulch was not a ‘thing’. People did not put annual layers of wood chips on their gardens and there were not bags of mulch for sale at garden centers. Wood mulch became popular with the Clean Air Act of 1970. Until then, sawmills burnt their extra sawdust and wood chips and tree bark.
This was a source of air pollution, so they sought an alternative use for their by-product. The National Forest Service reported that tree bark chips were a useful source of humus in the forest. From there, an American obsession was born. It has grown to the point where mulch is now manufactured specifically for gardens, sometimes from old pallets and other material that does not serve the purpose of enriching the soil, and is instead, purely decorative.
Drawbacks to Yearly Applications of Mulch
Hardwood mulches do have benefits in the garden; especially suppressing weeds and holding moisture in newly planted beds. However, the annual application of hardwood mulch to replenish what is lost each year to decomposition and sun fading can be a real chore and expense. Of course, there is a definite place for mulch in a new planting until the garden is established and as time goes on. Here’s a short list of some of the drawbacks of mulching excessively every year:
- Hauling mulch around in wheelbarrows and shoveling scoop by scoop, raking it smooth, and cleaning up the mess each spring is a chore. Possibly more difficult than the actual weeding.
- Weeds are still an issue! Even in the deepest of hardwood mulch, weed seeds find their way to sprout and take hold.
- And, not to mention, some mulch often comes with weed seeds!
- Excessive amounts of hardwood mulch applied at high volumes to garden beds can damage the soil and make it more difficult for plants to grow.
- Fresh wood chips can pull nitrogen from the soil as they decompose, leaving less of this essential element for your garden plants.
- Mulch does not protect your beds from erosion due to heavy rains, We’ve all seen mulch wash-out haven’t we? It leaves valuable soil exposed and vulnerable to being washed away.
- When deep mulch is pushed against trunks of woody plants or over the crowns of perennials it kills the plants. It takes several years to kill a tree, but perennial death is quicker.
An Ecological Alternative
From an ecological view, there is a very little benefit to wood mulch for wildlife, birds, and pollinating insects. For a garden to fill ecological niches, plants of the appropriate species must interact in a community. Different species of plants growing together create a natural space where garden visitors such as butterflies will find flowers to feed from, and host plants to lay eggs on. Birds can find a place to nest and also forage on the plants or the insects they support.
Instead of applying layers of mulch around sparsely placed plants, try planting short, spreading, perennial groundcovers between your larger garden plants. Let them fill in over time and replace the mulch as they grow. (Stay tuned for Part Three, where we will address how to gradually make this transition over a number of years.)
Sometimes we call these plants “green mulch” or “living mulch”, because like hardwood mulch, they suppress undesirable weeds, hold moisture, and cover areas of bare ground. At the same time, they allow larger, prized specimen plants to shine. And by using native plants to create plant communities in your landscape, your gardens will be more attractive and hospitable to songbirds, butterflies, bees, pollinators and other creatures.
By utilizing the right plants as green mulch you can reduce your annual hours of labor, suppress weeds, retain soil moisture, build a thriving plant community that can sustain beneficial insect populations. You can also avoid potential issues from hardwood mulches such as nitrogen leaching and plant damage, as well as create a beautiful and aesthetically pleasing, diverse garden or landscape. What’s not to like?