Welcome to Ask the Arborist, where we tackle your tree questions with a mix of science, experience, and just the right amount of caffeine. Now, I know it’s still winter, and you’re probably not thinking about soil. But here I am, sipping my coffee and pondering dirt—because what else would an arborist do in the off-season?
If your tree could talk, it would probably say, “Help! I’m starving down here!” (Or maybe just, “More mulch, please.”) The truth is, when a tree isn’t looking its best—yellowing leaves, sparse canopy, or just an overall sad, “please-water-me” vibe—most of the time, the issue isn’t above ground. It’s in the soil.
The Root of the Problem
Trees in the forest don’t have landscapers, yet they thrive. Why? Because they grow in rich, aerated soil that’s packed with decaying leaves, microbes, and all the delicious nutrients their roots crave. A natural forest floor is like an all-you-can-eat buffet for trees—organic matter constantly breaking down, replenishing nutrients, and keeping the soil nice and loose. If trees had Google, they’d give forests five stars.
Now, contrast that with your yard. Chances are, your soil is compacted from years of foot traffic, lawn mowers, and the occasional game of backyard football. It’s also low in organic matter, because every fall we humans diligently rake up all the leaves (aka, nature’s free fertilizer) and bag them up like trash. Your tree’s root zone is also probably fighting with a thick, thirsty lawn, which hogs all the water and nutrients like my kids at dinner.
Did you know that according to research, about 80% of tree health problems can be traced back to the soil? That means if your tree isn’t thriving, the first place you should look isn’t at the branches—it’s at the ground beneath. Poor soil means weak roots, and weak roots mean a stressed-out tree. And stressed trees are like stressed people—they’re way more likely to have issues. Except instead of venting on social media, they just keel over.
So, What Can You Do?
Fixing poor soil doesn’t have to be complicated. Here are a few simple things you can do to help your tree’s underground buffet get back to full service:
Mulch, but don’t volcano! A nice layer of decaying wood chips or shredded bark around the base of your tree (2-4 inches thick) will help retain moisture, regulate temperature, and slowly add organic matter. It also eventually loosens the soil. Just don’t pile it up against the trunk! Oh, and avoid landscape fabric. It’s evil!
Let leaves lie. Instead of bagging up all those fallen leaves in the fall, shred them with your mower and let them decompose. They’ll act as a natural fertilizer for your tree (and save you some work). Bonus: no more awkward raking battles with the wind.
Water wisely. Deep, slow watering is better than frequent, shallow watering. Trees prefer a long drink rather than a daily sprinkle.
Fertilization. Feeding your tree replenishes nutrients, promotes vigor, and helps reduce stress. But make sure you’re using the right type of fertilizer-and don’t overdo it! Overfeeding a tree is like force-feeding a kid an entire cake—it won’t end well.
The Bottom Line
If your tree isn’t happy, don’t just stare at the leaves in confusion—look down! Soil health is the foundation of tree health, and a few small changes can make a huge difference. A little love below the surface can keep your tree standing strong, shady, and beautiful for years to come.
And remember, if your tree is looking rough and you’re not sure what’s wrong, it’s probably not personal— just ask an ISA certified arborist to come out for a health check!
Mike White is an ISA board certified master arborist and owner of Treemaster LLC. If you’re interested in learning more about tree related issues, you’ll find him to be moderately obsessed. You can reach him at mike@treemasterllc.com
