The Problems Associated With Tree Surrounds

You see them in just about every part of the country — I know that I’ve seen them in each of the 40 states I’ve been to. Tree surrounds, or tree rings, are just an odd and head-scratching item in the arboricultural world. You see all types and varieties:

  • Small ones
  • Half-side ones
  • Large and deep ones
  • Dirt over roots, boulders and soil
  • Bricks filled with rock
  • Trunks buried in rocks or wood chips, sometimes referred to as mulch volcanoes

Why they’re used

Perhaps the most important consideration with tree surrounds is to gain an insight into why they’re there in the first place. After all, they cost money to install and need to be maintained. Four main reasons have been identified:

They hide ugly roots. Certain species such as maple, baldcypress and cherry tend to produce roots at or near the surface, in addition to ones deeper in the soil profile. Many clients consider them to be ugly and want them covered with soil or mulch. Others claim they’re a trip hazard, especially older folks. The “ugly” notion is up to the individual, however, there is a certain validity to the trip hazard rationale.

Tree surrounds can encourage stem girdling roots. All photos by John C. Fech, UNL

Grass won’t grow in the shade. Under trees with dense canopies, turfgrass struggles to thrive due to root competition and the shade itself. Turf is best thought of as a sun plant, with even the most shade tolerant species requiring four hours of sunlight. After several years of shade, bare soil usually results, and clients want a replacement plant, something/anything other than dirt or mud.

Tired of hitting their head on low branches. If turf is able to grow to some degree under a shade tree, the need to mow under lower scaffold limbs usually exists. And, naturally, as the focus of the mower operator is on the turf, sometimes they lose track of where they are and bonk their head on the branches that grow low to the ground. Ouch.

“Well, that’s what my parents did.” New, first time homeowners often report that they mimic their parents landscaping techniques, sometimes to a fault. For example, if mom and dad had a hedge, by golly, they want one too — until they realize that you have to shear the thing off several times a year and then gather up all the trimmings and do something with them. The same is true with a tree surround. They think, “If I have a tree in the front yard, then I need a tree ring to go with it.’

Why they’re bad

The previously-identified reasons are pretty strong in a compelling sense, so why is it important to discourage tree surrounds from being installed? Can’t we have both? Can’t we just all get along? Again, here are four reasons:

Soil on the trunk. In almost all tree-surround installations, a considerable amount of soil ends up in direct contact with the bark of the trunk — anywhere between 6 and 30 inches, or so. This usually results in the bark staying wetter than normal after a rainstorm and a reduction in the barks’ photosynthetic capacity. The loss of chlorophyll capacity isn’t that much of a problem, however, the bark being wet for long periods of time is, as it often leads to softening of the tissue and decay.

When mulch is piled on a trunk, it’s just as bad for a tree as a tree surround.

Cutting off soil oxygen. Fibrous roots need oxygen in order to expand and function well. If they’re covered with 2 feet of soil, that capacity is significantly reduced, much like people with asthma have trouble breathing under certain environmental conditions.

Encourages root girdling. Generally, when a tree ring is constructed, it’s filled with freshly-loosened soil to the top of the bricks/boulders/stones/timbers. In some cases, the property owner knows that shade-tolerant perennials or groundcovers grow best in amended soils, thus mixes compost with garden soil that exists on the site. When there’s a difference between the soil surrounding the tree and the amended soil (such as silty, compacted clay of new construction vs. compost or peat moss amended soil), the roots tend to preferentially stay in that, taking the course of least resistance as opposed to venturing out into the rest of the site. This causes circling roots, which eventually develop into stem girdling roots.

It’s just not natural! Maybe the best reason why tree surrounds are bad is that they’re not natural. When was the last time you were walking through a forest and found all those tree surrounds Mother Nature installed? My guess is never. If we’re supposed to follow her lead on tree care (yes, it’s best to follow it), we should avoid tree rings.

Solutions

Now that we’ve examined why they’re used and why they shouldn’t be there, what should be done with tree surrounds when we have a client with one?

This is a possible alternative to a tree surround.

First, if you take on a client with an older tree (one that has been there for more than 10 years), there’s not much you can do. Hopefully, by now, the roots are out in the landscape. If possible, move the soil away from the trunk without injuring it. If they’ve been there for a short time, say two or three years, remove the boulders/bricks/railroad ties. Examine the roots if they’re visible and be ready with mulch to pile loosely over the mound. This allows for a gradual transition of the roots to a more natural and well-functioning state.

If you’re fortunate enough to spot one that has been recently installed, it’s best to convince the property owner of its negative effects, rip out the hardscape and topdress with mulch. Again, make sure the mulch isn’t piled on the trunk. As much as possible, return the tree ring tree planting to a proper one.

Prevent future injury

As a responsible tree care provider, it’s important to let your current and future clients know that a tree surround is bad landscaping and poor tree care. In any way possible, it’s up to you to communicate the information presented above. Get on Facebook, Twitter and your company newsletter or blog and explain why tree surrounds are bad for trees.

Additionally, contact your friends and colleagues that design and install landscapes and make sure they understand why this is a bad practice. Also, communicate the fact they’re a key player in preventing tree surround installations. If they take your advice, the trees they plant will be healthier, last longer, provide more benefits to their clients and be assets in the landscape, rather than detriments.

Slopes present an extra stress on trees. Tree surrounds that cover only part of the root system are better than ones that cover all of them.

Alternatives to tree surrounds

The message shouldn’t simply be that “tree surrounds are bad.” Instead, it should be that “they’re bad, this is why and here are some alternatives.” To a certain extent, the alternatives are more of a landscape and planting design issue, but at a minimum, a couple of concepts are relatively easy to communicate and easy to understand:

  • First, instead of piling soil around the trunk, plant between or “shoehorn in” some shade-adapted plants between roots.
  • Placing vinca, lamium, lilyturf or Japanese spurge in the gaps works remarkably well both in terms of establishment and minimizing injury to the tree trunk and roots.
  • Another good alternative is even simpler: return the planted to a forest mimic, with mulch over roots pulled away at the trunk. Once the mulch breaks down a little, it becomes a good planting medium for shade-adapted landscape plants.

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