El Dedon Verde

Add Mulch

If you could only do one thing in your garden or landscape that would offer the most benefits for your efforts, add mulch!

I’m fond of saying there are three things you can do to eliminate 95 percent of your gardening challenges. You’ve already learned the first two. First, put the right plant in the right place. Second, feed the soil, and let the soil feed the plants. And third, add mulch.

Of all the ways I can suggest to save time and work in our landscapes and gardens while doing more for our plants and soil than you can imagine, the generous use of mulch is perhaps the easiest of all. It’s practically foolproof… and yet offers so many benefits. In all the years I’ve been using it, I can easily recall the rare times I failed to put mulch down over a new garden bed. And that season’s results were always disastrous compared to the other times.



One of the most loathed tasks for any gardener or weekend warrior is weeding. Now, mulch won’t guarantee a weed-free landscape, but it does greatly suppress seed germination by blocking sunlight to the soil surface. And just as with the things you want to grow in your garden, if weed seeds don’t get adequate sunlight, they won’t germinate.

But unfortunately, weeds have the maddening ability to sprout and grow in even the most challenging conditions. Birds, wind, pets, and people will always be couriers of weed seeds, so they’ll still sprout in your mulch. But when they do, they’re easier to pull out since they’re rooted in the loose top layer of mulch.

If you’re not convinced, do a side-by-side comparison in one of your garden beds. Add mulch to half; leave the other uncovered. It should only take a few weeks for you to become a mulch disciple like me.


You don’t need to be a horticulturist to know just how quickly exposed soil surfaces can dry out under the hot baking sun. Over time, moisture below the surface evaporates away, progressively drying out more deeply with each passing day. Unfortunately, many plant roots grow within the top few inches of soil and suffer when those exposed soil surfaces become dehydrated. Conversely, a three-inch layer of mulch acts to provide a protective, insulating barrier from the evaporative effects of the sun and heat and helps the soil to retain precious moisture far longer and more deeply.


Similarly, that same layer of mulch moderates soil temperatures, keeping temperatures below grade cooler in summer and warmer in winter. Think of mulch as a thermal insulating blanket. Having a generous layer of mulch around your plants and trees can literally make the difference between life and death when it comes to extreme temperatures in both summer and winter.


Many disease pathogens reside in soil. They can easily be splashed up onto plant foliage by precipitation or irrigation. That’s a common way plants become infected. Once again, mulch reduces the chance of this happening by providing a physical barrier, a protective layer that blocks the splashing effects of pathogens and keeps them from making it onto the plant stems and leaves.


We’ve already had a thorough discussion of the importance of adding organic matter to improve soil. Any natural wood or plant-based mulch is a great source for this to improve the soil as it slowly breaks down and decomposes. It’s a two-for-one proposition, giving you all the benefits of mulch as well as adding organic matter all in a single step.


Surely you’ve noticed just how hard and crusty the soil surface gets when exposed to the elements. As such, the ground becomes impenetrable, precious top soil has nothing to protect it, and when it rains, there’s nothing to buffer the pounding drops or to hold soil in place. All of that adds up to the loss of precious topsoil, erosion, and destructive runoff. And all of that can be eliminated with a minimal layer of mulch. It’s such a no-brainer it’s hard to imagine that there are gardeners who don’t mulch.


Finally, there is no denying the eye-pleasing appeal that mulch adds to any landscaped bed. On top of the valuable benefits mulch offers to the health of our plants, a generous layer of mulch adds the finishing touch that complements and sets off your landscape or garden beautifully.If your landscape needs a quick-fix kind of spruce-up, even if you don’t do anything else at all, a top-dressing of fresh mulch to the beds offers an instant TV-yard-makeover punch.


Although any natural mulch will decompose over time, adding carbon and other important matter to the soil, some mulch can add other materials you would never want. This can include chemicals like arsenic from pressure treated wood. Play it safe with the mulch or soil you buy and look for the certification seal from The Mulch and Soil Council on approved bags. It assures the product you’re buying is free of chemical materials**.


There are many options when it comes to types of mulch. Choosing the “right” mulch is a matter of taste; but there are some pros and cons to consider with each. Organic mulches break down over time and eventually must be replaced. Bark mulch is the most common and comes in several sizes and types. The larger the pieces, the more slowly it breaks down.

Shredded wood can be slightly fuzzy, so it will cling to itself, making it a good option for slopes. I use this type most often as it looks great and breaks down slowly. And I do want it to break down… just not so fast that I’m having to replace it all the time. At my place, a 3-inch layer of mulch will last about 3 years before I need to replace it.

Other forms of organic mulch include pine needles, which look great in beds and can help to acidify soil; use them around acid-lovers like blueberries and azaleas. Another favorite is wheat straw. The large bales are easy to work with; I like this best for use in a vegetable garden.

Alternately, you may prefer a more permanent solution such as gravel, stone, lava rock, or brick chips. They don’t add any nutrients to the soil, but they don’t break down with time, which, depending on your objectives, can be good or bad. Crushed oyster shells neutralize acid soil and alkalize neutral soil. Brick chips, crushed stone, gravel, and poultry grit are pricey but last for many years.

No matter the mulch of choice, the idea is to create a blanket over the soil roughly 2-4 inches thick. Too much and you can actually impede the flow of water reaching the soil surface.

When planting seeds, mulch around the bed, but leave the soil exposed to light and warmth until the seedlings have sprouted and put on some growth. Spread mulch completely around the root zones of new transplants to stabilize temperature and moisture, but keep it pulled back about an inch from stems and leaves close to the surface.

For newly planted trees, be sure to apply mulch out to the dripline or beyond. But by all means, avoid creating “mulch volcanoes” around tree trunks. Covering the trunk will limit air circulation and encourage insects and disease. ​