To new gardeners, mulching may seem like some sort of alchemical art: Someone throws some wood chips or dry leaves on a pile of dirt and (presto chango) a few months later they have beautiful, healthy garden soil or gorgeous, care-free perennials sprouting from the ground without weeds or work. It’s like magic. Well, this magic is really just a matter of knowing a bit about mulching.
What is Mulch?
Many of the benefits of mulching flow from what it is: mulch is a protective, insulating layer of material that’s put over soil or around the bases of plants. By acting as a barrier between the ground and above-ground environment, mulch ends up impacting your garden in a slew of ways. And, depending on the type of mulch used, it can do wonders to protect and nourish your soil and plants. But, if used improperly, it can just as easily damage them.
The benefits reaped from mulching mostly depend on which of the two types of mulch you choose to use: inorganic or organic. Inorganic mulches are mulches made from materials that are not plant-based. These can be rocks (stone, lava rock, pumice, etc.) or they can be synthetic materials like pulverized rubber, plastic sheeting and garden fabric (also often called landscape fabric, weed cloth and weed barrier). Organic mulches are made from plant-based materials. (So, in this context, organic refers not to the quality of the mulch but to the origin of the mulch.) Organic mulches can be made from all sorts of materials, like wood chips, pine needles, hardwood and softwood bark, hay, straw, cocoa shells, leaves, pecan hulls, cut grass, compost mixes and even newspaper.
While many organic mulches are readily available regardless of your region (like wood chips and leaves), the availability of some organic mulches may be related to local industries and agriculture. For instance, some areas may have fruit or berry mulches available whereas other areas won’t, just because there isn’t a local industry to produce the byproduct. The neat thing is that different types of organic mulches have different nutritional profiles themselves, so different types of organic mulches can affect your soil in different ways.
The Many Benefits of Mulching
- Improve moisture retention. By reducing surface evaporation and helping to maintain moisture, mulching reduces the overall need for watering. Not only does that promote sustainable living, it reduces water costs too.
- Improve soil structure and soil nutrient levels. Because organic mulches are made from biodegradable, plant-based materials, they decompose. And as they decompose, organic mulches replenish soil nutrients, affect soil structure and increase microbial activity, all of which improve plant health and reduce the need for soil amendments. Essentially, mulch can act like a slow-release nutrient bank that works and feeds your soil on its own schedule. What’s easier than hands-free fertilizer?
- Improve aeration. Organic mulch decomposition and microbial activity encourage earthworm habitation, and as any gardener will tell you, an earthwormy garden is a happy garden. Earthworms are little dirt farmers themselves who improve soil structure and disperse soil nutrients throughout your garden bed. As they do so, they improve air movement and water penetration, stimulating plant and root growth.
- Control weeds. By acting as a barrier that prevents weeds from getting the sunlight they need to thrive and spread, proper mulching can make a huge difference when in it comes to controlling weeds. What’s easier than hands-free fertilizer? How about hands-free weeding? Just lay your mulch down and it will do the rest.
- Reduced maintenance. Less time weeding, less time fertilizing, less time watering and less time amending your soil can mean a lot less time doing routine maintenance in your garden. And, while I love spending time in my gardens, I’d much rather spend it doing fun things like harvesting and snacking, not weeding and whining.
- Protection from heaving. During cold seasons, small and/or shallow-planted bulbs can be pushed out of the ground (called heave or frost-heave) and roots can suffer frost damage. Mulching helps control temperatures, protecting roots and bulbs from these effects of extreme temperatures and changes in soil temperature.
- Temperature control. Just like mulch insulates the ground in winter so that the soil freezes and thaws gradually, mulch controls cooling in the heat of summer, preventing plant roots and soil from extreme heat and related stress. Less stress means healthier, stronger growth and less susceptibility to disease.
Weighing the Benefits: Organic vs. Inorganic Mulches
While there are plenty of differences between organic and inorganic mulches, regardless of the type of mulch you choose, if used properly, any mulch will inhibit weed growth, slow water evaporation and reduce maintenance time. It’s just that there are a lot more benefits associated with using organic mulch instead of inorganic mulch (like improved soil structure, improved aeration and improved soil nutrient levels). But that doesn’t mean that there aren’t drawbacks too. For instance, while inorganic mulches don’t improve soil structure, that also means they don’t harm it either.
If you use an inorganic mulch, you don’t have to worry about it adversely affecting your soil composition or pH. On the other hand, because organic mulches do break down and have nutritional value, they can attract insects, slugs and even rodents. Plus, organic mulch can even go bad if not handled properly. In fact, there are plenty of problems associated with improper mulching, so there is no “right” mulch to choose; it’s all a matter of picking the mulch that works best for your situation and gardening style.
- Use 2 – 4 inches of mulch. Using less mulch is rarely effective and using more will be a waste (or worse, will stress your soil and plants).
- Don’t use organic mulches that smell like ammonia or sulfur. Strong smells like these are indicators that the mulch is bad and using it can lead to a bunch of mulch problems.
- Don’t put mulch over the crowns of plants. Instead, keep mulch a few inches away from plants and plant bases to discourage garden pests and fungal diseases.
For more information about keeping a healthy and happy garden, check out the Gardening Guides page. There you’ll find plenty of gardening resources and in-depth guidelines for growing your favorite herbs and vegetables.