Spring Gets All the Credit, But Summer Is When Mulch Earns It

There’s a general sense that mulching is something you do in the spring — freshen up the beds, make things look nice, check it off the list. And spring mulching is genuinely worthwhile.

But if you mulched in March or April and haven’t thought about it since, it’s worth taking another look right now. Because the work that mulch does in July and August — during the sustained heat of a Chattanooga summer — is probably more important than what it does in April.

What Mulch Actually Does in Summer Heat

Chattanooga temperatures regularly stay above 88 degrees for 60 or more days a year. Without any ground cover, bare soil loses moisture to evaporation fast — within hours of watering on a hot day. A 3-inch layer of mulch dramatically slows that evaporation, keeping soil moisture available to roots for much longer between waterings.

Beyond moisture retention, mulch insulates the soil from temperature extremes. The root zone of a tree in direct summer sun can get significantly hotter than the air temperature. Mulch buffers that. Cooler roots are less stressed roots.

It also reduces soil compaction — an underappreciated benefit in Chattanooga’s clay-heavy soil, where the surface can bake into something approaching concrete by mid-July. Compacted soil prevents water from penetrating, which means even when it does rain, the water runs off instead of soaking in. Mulch keeps the soil structure loose enough for water and oxygen to move through.

What to Check on Your Existing Mulch

If you mulched in spring, check the depth now. Three inches is the target. After a few months of rain, foot traffic, and natural decomposition, a spring mulch layer can thin down to an inch or less in spots. At that depth, it’s not doing much.

If your mulch has thinned below 2 inches, adding a fresh layer now — just enough to bring it back up to 3 inches — is one of the lowest-effort, highest-impact things you can do for your trees and beds this summer.

One thing to watch for: if the existing mulch has formed a dense mat on top that sheds water rather than absorbing it, rake it lightly to break it up before adding new material on top. Compacted mulch can actually repel water rather than hold it.

The Volcano Problem

While we’re here: if you’ve ever seen mulch piled up into a mound against a tree trunk — sometimes a foot or more high — that’s called volcano mulching, and it causes real problems.

Mulch piled against the trunk holds moisture against bark that isn’t designed to stay wet. Over time, it can cause rot at the root collar, attract insects and disease, and actually kill a tree from the bottom up. It’s a very common mistake, often done with good intentions.

The right approach is a flat, even layer — think donut, not volcano. Keep the mulch 2 to 3 inches away from the actual trunk, spread it outward to the drip line, and keep it at 3 inches depth across that area.

What Kind of Mulch Works Best

For trees specifically, organic mulch — wood chips, shredded hardwood, double-ground bark — is generally the best choice. As it decomposes, it adds organic matter back into the soil, which improves structure and supports the biology of the root zone over time.

Dyed mulch performs the same functional role; the color just helps it look fresh longer. In Chattanooga, between the sun and the rainfall (we get around 52 inches a year), natural mulch tends to gray out within a few months. Dyed mulch typically holds color for closer to a year.

Pine straw is another option — it’s lighter, easier to spread over large areas, and works well. It’s a bit less effective at weed suppression than hardwood mulch, but it breathes well and is a good choice for slopes where mulch tends to wash.

Avoid rubber mulch around trees. It doesn’t decompose, doesn’t add anything to the soil, and can actually heat up in direct sun and raise soil temperature.

The Beds Matter Too

While you’re thinking about tree mulch, the same principles apply to foundation beds and flowerbeds. Summer is hard on everything in the ground. A fresh layer of mulch in your beds now will significantly reduce watering needs through the rest of the season, keep weeds suppressed during their peak growing period, and protect roots from the heat.

We Can Help With This

Mulch and flowerbed installation is part of what we do, and summer is an underrated time to get it done. If your beds and tree rings are looking thin, or if you want a fresh layer put down properly — including proper technique around the trunks — give us a call or text at (423) 443-4533.