In the gardening world, few practices are as universally beneficial yet often overlooked as the application of mulch. Mulch is a catch-all term for material - whether organic or inorganic - that is spread over the soil. You are probably used to seeing wood chips or straw used as mulch, but plastic sheeting, cardboard, ground rubber, and even gravel are also used. Mulch as a whole has many benefits, and each material excels in different areas. In this article, we will discuss the different benefits that mulch offers and which materials stand out in each use case.
Soil Moisture Retention
What Is It: Anyone who has ever cared for a plant will notice that water evaporates from the soil, drying it out and requiring you to water it more. Covering the surface of the soil in mulch will help prevent this, both by keeping evaporated water from easily escaping and by shielding the soil from direct sunlight. This action helps to keep the soil moist and reduce the amount and frequency of watering required to keep your plants healthy.
Which Mulch to Use: The best mulch for this is plastic sheeting, with cardboard in a close second. Plastic doesn’t allow for the exchange of moisture with the air except for near-open edges, such as the holes around plants, and even those areas can be weighed down with something (such as wood chip mulch) to keep the area sealed. If you’re not interested in further contributing to the micro-plastic epidemic then look to cardboard as your next best option. It is much more biodegradable than plastic but still offers a solid barrier against sunlight and evaporation. If you want something that will work well without making your backyard look like a recycling plant, then straw and wood chips are your best options, though they’re not quite as good at moisture retention as plastic sheeting or cardboard.
Gravel is the worst option for soil moisture retention due to the many relatively large gaps between the pieces, which is a shame because gravel looks best in exactly the kind of dry climates where moisture retention is most important!
Temperature Regulation
What Is It: Plants care about temperature just as much (if not more than) we do, and the area around their roots is especially important. Mulch acts as a thermal regulator, keeping the soil cool in the summer and warm in the winter. This can keep plants healthy and productive further into the cool season than they would be otherwise and can help plants weather extreme heat in the summer.
Which Mulch to Use: This may not be the most scientific answer - talk to your local university’s ag extension for that kind of info - but we think straw is the best overall at thermal regulation. The many small, overlapping pieces of straw help insulate the soil better than mulches with a more open structure, like gravel. In the cooler months, decomposition of the material will even lend some additional heat to the ground as microbes break the straw down. Black plastic sheeting is also a good option, as the black surface will help the sun warm the ground even when it’s cool outside, despite the fact that a thin sheet of plastic isn’t the warmest material in the world.
Weed Suppression
What Is It: Everyone knows weeds, and nobody likes them. Covering the soil with mulch is a good way to keep them under control, as the lack of sunlight on the ground and the many obstacles in the way of a newly sprouted weedling prevent them from growing unimpeded. Proper use of mulch can drastically reduce or even eliminate weeds, all without using any herbicides.
Which Mulch to Use: Here again we see plastic sheeting come out ahead, as it is just as impermeable to weeds as it is to water. That being said, the real answer here is weed mat. The weed mat is a decent mulch by itself, but the woven fabric material is designed to be permeable to water and sunlight while entirely preventing weeds from sprouting through it. If you put the weed mat down first, you can put whatever you want on top of it and have it be just as effective as plastic sheeting at fighting weeds. You’ll need to be vigilant for tears in your weed mat, especially if you have gravel on top of it. If you don’t, the weeds growing up through the tear will show it to you soon enough!
Soil Health Improvement
What Is It: Soil is an ecosystem on a very small scale, and the health of that ecosystem determines how well your plants will grow in it. Healthy soil provides a safe environment for the many microbes living in it and a structure conducive to root growth, among many other things.
Which Mulch to Use: Organic is the name of the game here, as anything that can decompose will help nurture the soil. Wood chips and straw are both great options that will eventually break down, adding their nutrients to the soil and making it better over time. If you’re familiar with making compost, you can basically use anything that you’d use for the carbon side of the compost equation as mulch and it’ll be good for your soil health. Some of those items might not be practical (looking at you, grass clippings!) or attractive, but they will all eventually break down and make your soil better.
Plastic and gravel are the worst options for this. Broken down plastic will do your soil health no favors, and while gravel might technically be good for breaking up dense soil structures, using an organic material will be much better.
Erosion
What Is It: Erosion is the removal of soil due to physical factors like wind and rain. Bare, uncompacted soil will wash away in the rain or blow away in the wind, leaving you with less soil to work with. Since compacted soil is bad for your plants, your best option is to keep your soil safe from the elements.
Which Mulch to Use: When it comes to wind, anything you put over the top of your soil will help. Anything is better than nothing when it comes to rain, but things that can soak up water or prevent it from hitting the soil entirely are best. Wood chips and straw do a great job of both covering soil against wind and keeping it from being inundated by rain, both of which reduce erosion. Plastic sheeting is a good option too as long as it’s properly weighed down, though it will channel rainwater out to uncovered areas, where it won’t be available to your plants and may cause erosion issues. Gravel, as usual, is the worst option, as it does nothing to help soak up water.
Aesthetics
What Is It: It’s how it looks! Aesthetics are an important part of any garden, even strictly functional ones.
Which Mulch to Use: Whichever one you like! When it comes to aesthetics, all that matters is whether you like the way it looks. Even the worst mulch, like gravel, can be paired with other materials to shore up its weaknesses. If you see a mulch that you love but it’s not ideal for one of the topics we discussed above, don’t count it out. Just combine it with another type of mulch!
Mulch and Drip Irrigation
Mulch is a great option no matter how you’re watering your garden. That being said, it does work best with drip irrigation. Drip irrigation can be placed underneath your mulch of choice, which means the water will go directly into the soil instead of having to penetrate the mulch first. This means shorter watering times and less water used. Some types of mulch, like plastic sheeting and cardboard, will even prevent a sprinkler from watering your plants at all unless the mulch is removed prior to watering.
Whether you're the green-thumbed guru of your neighborhood or a budding gardener whose experience is currently more about enthusiasm than expertise, we’re here to help. The journey from 'seedling' to 'full bloom' is paved with support from experienced people. If you're itching for a nudge in the right direction, looking to take a deep dive into the wonderful world of drip irrigation, or just want a friendly chat about how to make your garden better, The Drip Store is here for you. Our team is ready to help you make your gardening dreams come true.
