By: Teo Spengler
You may worry about getting thicker around the middle, but the same rules don’t apply to your trees. In the wild, tree trunks flare out just above the soil line, indicating where the root system begins. Exactly what is a tree flare? Is root flare important? Read on for root flare information.
If you aren’t experienced with tree planting, you may be curious about tree flares. A tree flare, also called root flare, is the broadening of a tree’s trunk just above the soil line. Is root flare important to a tree’s health? It is very important as an indication of where the trunk ends and the root system begins.
Most roots are found in the 12 inches (30 cm.) of soil just below the tree flare. They stay close to the top of the soil in order to complete the oxygen exchange, essential for the tree’s survival.
When you are planting a tree in your backyard, root flare depth is of prime importance. If you plant the tree deep in the ground so that the root flare is covered with soil, the roots cannot access the oxygen the tree requires. The key to determining root flare depth when you are planting is to make a point of finding the root flare before putting the tree in the ground. Even in container grown or ball-and-burlap trees, the tree flare can be covered by soil.
Carefully remove the soil around the tree’s roots until you locate the tree flare. Dig a planting hole sufficiently shallow so that when the tree is placed in it, the flare is fully visible above the soil line. If you are worried about disturbing the tree’s roots, dig a hole to the proper depth and place the entire root ball in it. Then remove the excess soil until the root flare is fully exposed. Only then backfill the hole up to the base of the root flare.
You may get the tree in the ground and wonder if you’ve done it wrong. Many gardeners ask: should I be able to see a tree’s roots? It doesn’t hurt a tree to have some of its top roots exposed. But you can protect them by covering them with a layer of mulch, right up to the base of the root flare.
Remember that the root flare is actually part of the trunk, not the roots. That means it will rot if consistently exposed to moisture, as it will be under the soil. The tissue that rots is the phloem, responsible for the distribution of energy manufactured in the leaves.
If phloem deteriorates, the tree is no longer able to use food energy for growth. Adjusting for proper root flare depth is essential to maintaining a healthy tree.
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Mulch your tree with a 3-4” depth organic mulch over roots out to dripline of tree (outer edge of branches/crown). This needs to be replenished every year. Mulch will help
conserve moisture for roots,
reduce competition of weeds and turfgrass with tree roots (they often outcompete!),
provide a layer of nutrients to cycle back into soils (organic matter that is often lacking in urban areas) and
keep string trimmers & mowers at bay (to avoid root/trunk damage).
Clemson Extension's Home & Garden Information Center (HGIC) provides research-based information on landscaping, gardening, plant health, household pests, food safety & preservation, and nutrition, physical activity & health. HGIC is designed to complement Clemson’s network of professionals and volunteers by answering the routine types of calls and thereby freeing agents to deal with commercial agriculture/horticulture questions and conduct proactive programming to larger audiences.
Trees are the long-lasting framework of our landscape. Follow these important planting tips to insure the health and longevity of your plants.
Make sure the root flare, the place where the roots flare away from the trunk, is at or slightly above the soil surface.
Dig the planting hole the same depth as the distance between the root flare and bottom of the root ball. Digging deeper can result in the soil settling and creating a water collecting depression around your tree. Make the hole at least 3 to 5 times wider than the root ball.
Roughen the sides of the planting hole to avoid glazed soil that can prevent roots from growing into the surrounding soil.
Remove burlap and wire baskets that can interfere with rooting and eventually girdle the roots.
Water thoroughly at planting and whenever the top 4 to 6 inches of soil are crumbly and slightly moist.
Spread a 2 to 3 inch layer of wood chips over the surrounding soil. And pull the mulch away from the trunk of the tree to prevent rot and disease.
Wait a year to fertilize your newly planted tree.
A bit more information: Always call 811, the free utility locating service, at least three days before planting. They will locate underground utilities so you can avoid damage and personal injury caused by digging into buried utilities.
Trees provide shade. they offer habitats for wildlife. they share their branches for swinging and climbing. and additionally, they are a great investment in the future of your property. With all of the benefits trees offer, it’s important to give them the best possible start by planting them correctly. Mistakes made in planting can cause tree problems for years to come. Here’s what you need to know to plant a tree properly.
Choose a young tree. Pick one grown in a container with a trunk no more than 1 inch in diameter. Older, larger trees are more difficult to plant, and it’s also harder for them to recover from the shock of transplanting. A younger, smaller tree grown in a container will start growing more quickly.
Handle with care. The bark of young trees is thin and easily damaged. Carry the tree by its pot and avoid handling the trunk or branches.
Don’t plant the tree too deep. This is the biggest mistake you can make. The trunk flare—the place where the trunk curves out to meet the roots—must be at or above the level of the surrounding soil. To know how deep you should plant your tree, find the trunk flare (you may need to feel down into the soil often the trunk flare is buried in the pot). Use a yardstick to measure the distance straight down from the level of the trunk flare to the bottom of the pot. This is the depth of root ball.
Dig a wide, shallow hole. Make it more like a saucer than a bucket, with sloping sides. At the center, it should be no deeper than your measurement of the root ball. Check the depth by laying a shovel or rake flat across the hole and measuring down from the bottom of its handle.
Gently remove the tree from the pot. You may need to roll the pot back and forth to loosen the root ball. Slide it from the pot near the edge of the hole. Inspect the roots. Look for roots that are circling around the root ball they can choke the growing tree. Cut them with sharp pruners or a sharp knife. If there are many circling roots, use your knife or a sharp spade to slice about 1 inch from each side of the root ball. New roots will sprout and spread out from the cut roots.
Place the tree in the hole. Check to make sure the root flare is at the level of the surrounding soil or 1 to 2 inches above that level (over time, the tree may settle). Make sure the trunk of the tree is upright and that it’s facing the right way. Usually, the best-looking side should face the street or the window from which you’ll be viewing the tree.
Fill the hole. Use the same soil you removed, without adding compost or any other amendment. After filling the hole halfway, double-check that the tree is vertical from every angle. Gently pack the soil down with your feet. Then fill the hole the rest of the way. Don’t pile soil on top of the root ball or bury the root flare. If you have too much soil, spread it out around the hole.
Water. With a hose or buckets, gently pour at least 10 gallons of water onto the root ball and over the rest of the hole to settle the soil.
Mulch. Spread wood chips or shredded wood mulch in an even layer about 3 to 4 inches deep in a wide circle around the trunk. The wider the mulch circle, the better. Do not pile mulch against the trunk of the tree. Pull the mulch 3 to 4 inches away from the bark. Skip staking and pruning. There is rarely any reason to stake or prune a young tree when planting it.
Keep watering. For the first two years, water the tree slowly and thoroughly every week or two. It will take that long for the tree to grow enough new roots to collect sufficient water from rain. Careful attention when the tree is young will provide the necessary foundation for it to flourish for years to come. And one more thing. take a picture of your family by the tree each year to appreciate how the tree - and your family - are growing!
Tree fanciers all have one thing in common. We all plant trees incorrectly. More specifically, we all plant trees too deeply. Maybe 10 percent of the people reading that sentence are thinking, "Yes, most everybody else does plant trees too deep, but not me."
Well, I'm talking about you, too. Everyone plants trees too deeply. It seems to be ingrained in us.
Many of us have perspired over a newly planted tree envisioning someday, someone resting under its green shade, staring blissfully at a robin's nest in its branches, or watching a deer grazing on its acorns on a crisp fall afternoon. However, by planting trees too deep in the soil, we dramatically reduce the tree's capacity to ever reach its potential.
How is it that our tried-and-true tree planting methods are not so true? For starters, trees are planted too deeply at the tree nursery. Compounding the problem, modern tilling practices to control weeds at nurseries tend to throw dirt on top of tree roots, burying them even more. The trees we purchase these days come to us with up to 12 inches of extra dirt on top of their roots.
I think almost everyone assumes that the roots of the trees they have purchased are just under the soil line of the container or burlap. They're not. You might already have six or more inches of soil above the roots.
We compound the problem when we dig a little deeper hole for the soil ball to ensure the tree is anchored solidly and is well braced.
To top it off, we often encase the lower trunk in a big pile of mulch, entombing the roots more deeply.
Take a critical look at the trees in your yard or local park. Do the tree trunks flare out at the base, or do they tend to look more like telephone poles, going straight down into the ground with no root flare? The lack of flare is likely because the roots are buried too deeply. If, however, you look at trees that were not planted but grew naturally, notice how all of their trunks flare out at the ground (except pines).
Does it really matter if trees are planted too deeply? The answer, we are beginning to understand, is yes.
When tree roots are planted too far underground, secondary roots grow toward the surface to compensate. Rather than growing up and then out from the tree, some roots tend to grow up and then in or across, close to the trunk. Sometimes they even grow around the trunk.
For the first few years, these oddly growing roots don't seem to have any effect. As the tree matures, the buried trunk grows into these roots. Usually, about 10 to 20 years after a tree is planted too deeply, these roots girdle the underground trunk like a noose. The results are slowed growth, lost tree vigor, and premature death. In fact, a five-year study by the University of Minnesota shows that more than 80 percent of sugar maples that were in decline had stem girdling roots.
Besides stem girdling roots, trees that are planted too deeply often have problems with below ground trunk rot and root suffocation. Likewise, when a tree's roots are too deep, the tree tries to produce a whole new system of roots at the correct depth. This also slows the tree's growth and reduces vigor.
No matter what form of tree you choose to plant, whether balled-and-burlaped, container-grown or bare-root, the key is to determine where the topmost root (called the root flare) is growing off the trunk. You then have to ensure that the root flare is at (or ideally just above) the soil grade of the planting site.
Balled-and-burlaped trees are more cumbersome to handle than container-grown trees, and their soil balls often fall apart when unwrapped. Therefore, the method for planting differs slightly.
For balled-and-burlaped trees, probe the top of the soil ball close to the trunk to find the first roots. You can do this with a knitting needle, a clothes hanger or a stout wire. Measure the distance from the top of the soil ball to the root flare. Next, subtract that distance from the total depth of the burlaped soil ball. For instance, if you probe down 5 inches before you find the root flare, subtract 5 inches from the total depth of the burlaped soil ball. You should dig a hole to that depth, or even 1 to 2 inches shallower.
The width of the hole should be wider than the root ball. It is also good to break up the hole edges with a shovel so that emerging roots have looser soil to penetrate. However, the bottom of the hole should be firm. By digging the hole after measuring the root ball, you ensure the planted tree will be at the proper level.
Place the balled-and-burlaped tree in the hole and ensure that the trunk is straight. At this point the soil ball is still intact. After positioning the tree correctly, cut away the burlap and wire cage from the ball. Also, remove any twine or wire that is wrapped around the base of the trunk.
Next, use a spade to remove all of the dirt on the root ball above the root flare. At this time it is good to lay your shovel handle flat on the ground across the planting hole and check to see that the root flare is at or 1 to 2 inches above the soil grade of the planting site. If so, then fill soil back in the sides of the hole being sure not to add soil on top of the root flare.
Container trees are lighter than balled-and-burlaped trees, and their soil balls tend to remain intact when disturbed. Therefore, you don't need to use a wire probe to find the root flare. Instead, pull the soil ball out from the container and remove the excess soil off the top of the soil ball until you find and uncover the root flare. Then, measure the depth of the "new" root ball and dig the planting hole to that depth or 1 to 2 inches shallower.
On container-grown trees, roots may have already begun to encircle the trunk. Straighten or loosen any of these roots to keep them from eventually becoming girdling roots.
The root flare on a bare root seedling is much easier to spot since it will not be hidden in soil. Check to see that the roots are not growing in a J-shape or encircling the trunk. Then, plant the tree in a hole as above.
When you finish installing the tree, thoroughly soak the entire planting hole, including the root ball, with water. Then, add mulch 2-3 inches deep and as wide as you like around the tree. Keep the mulch off the trunk. Your mulch ring should end up the shape of a flattened doughnut, rather than a volcano. Stake the tree only if necessary using a soft, loose tie that will not abrade the young bark of the tree.
This new method for tree planting is no more strenuous than what most of us have been doing all along. The difference is in finding the root flare before digging the hole, uncovering the flare from excess soil, and not planting the tree too deeply. This will help your tree reach its potential much faster and improve its vigor.
For more information on how to plant trees and to obtain a free diagram, contact your local Missouri Department of Conservation forester.
A video titled Preventing Stem Girdling Roots details this method of planting trees. It can be ordered in Spanish or English from the Minnesota Nursery and Landscape Association. Call 615/633-4986 for ordering information.