The next time you’re fishing for a conversation starter at a cocktail party, try this line: “So how’s your root flare?” OK, you probably won’t get much more than a blank stare, or a “huh?” in response. How about at your next gardening party, then?
Of course, you should probably have some idea what root flare is, first. The root flare is the top of the roots, at the point of the tree where the trunk ends and the roots begin.
Think of the trees you’ve seen growing naturally, in the wild. Most of them have this. It is the preferred way to grow among trees. All the best trees are doing it. Unfortunately, most homeowners didn’t consult the local trees before planting theirs.
If you still aren’t sure what the root flare is, there’s a simple way to find out. Ask a child to draw you a picture of a tree. Most of them will do it right, with the root flare included.
See how the base of the tree flares out to the right and left? Kids know what trees are supposed to look like.
It is particularly noticeable on cedars (see top image), but any kind of tree should have at least a slight one.
Keep the Flare above Ground
It is imperative when planting trees that you keep this root flare above ground, just as it occurs in nature. What will happen if you don’t get this right? “Bad things, man. Bad things.”
If the root flare is buried, it will rot. It won’t happen overnight, but it will eventually happen. If you’ve ever had a tree that was healthy for many years, and then suddenly died with no clear indication of a problem, it may have been because the root flare was underground and it finally rotted to the point of killing the tree. That’s bad!
Another reason to keep the flare above ground is that it prevents planting the tree too deep. Roots need oxygen to do their job. Oxygen gets pretty scarce in the soil once you get down about 18 inches or so under the surface. When a tree is planted at the proper depth, the roots grow just under the surface and fill that 18” layer. When the tree is planted too deep, the roots have to grow back up to try to find the air up there, and often this leads to what is called tree girdling. That’s when the roots encircle the tree. When they do that, they mess up the tree’s ability to grow, and they can even kill the tree. That’s bad!
Care for Your Trees’ Root Flare
What if it’s already too late? What if your trees are already in the ground and you don’t see any root flare? Don’t despair! Carefully dig away the soil from around the base of the tree until you find that flare. Use a plastic trowel or shovel so you don’t cut a big gouge into the tree. Once you’ve located the flare, continue to scrape away the soil until you have freed the flare all the way around the tree. You also need to dig outward away from the tree so the tree isn’t sitting in a pit in the ground.
When mulching around your tree, don’t pile up the mulch around the base of the tree. In fact, you can leave 6 inches between the root flare and where the mulch starts. That way there is no risk of the mulch piling up and causing the trunk to rot. If you already have mulch piled up against the tree, go outside right now and scrape it away. I don’t care if it’s raining, your tree’s life depends on it. Go scrape away the mulch, leaving at least a few inches between the root flare and where the mulch begins.
Now you are armed to begin a great discussion at your next gardening shindig! And more importantly, you are ready to grow stronger, healthier trees.