Parks, Recreation & Leisure

Parks, Recreation & Leisure / Parks & Forestry

Landscaping Tips

Planting Under Mature Trees is not an Easy Task
I am often asked which plants do well under mature trees, with similar stories from homeowners attached to the question – first they tried growing turf under it, next they tried a landscaped flowerbed beneath the tree – with both efforts unsuccessful.

Unfortunately, there are few plants that do well or even survive in this difficult environment. While not an impossible task, planting under trees requires patience, flexibility, and knowing the limits of what you can achieve.

Size and species of the tree has a lot to do with the equation. If the tree is relatively small or hasn’t been planted for more than a few years, planting turf or a garden around it will likely be easy. It’s the 50-year-old-and-up trees dominating the yard that cause the most problems, especially maples (sugar and silver maples being the worst), sweet gum and various evergreen species. These trees have many shallow surface roots, which is the primary problem. Tree species such as oaks and black gum are more tap-rooted, therefore easier to plant under.

Whatever you do, don’t attempt to remove or intentionally damage these large roots from the surface or below the soil. This can stress the tree, inviting insects and disease, with the tree possibly dying from root damage, or its inability to take up enough water or nutrients. Plus, many of these large roots serve as anchors to hold a tree upright and, if damaged or removed can place the tree can be in danger of falling or being blown over in a storm.

The two biggest growing challenges caused by large trees are dense shade and root competition for water. The surface roots that cause planting and mowing nightmares are the same ones that compete with your new plants for water, and the mature tree will usually win.

Unless we have a hard rain, plantings underneath a dense canopy may receive little or no water. Mature trees have adapted to tough conditions like drought and have an extensive root system that quickly absorbs any available water. Because of this, plantings beneath trees require frequent soakings especially during dry periods, not just when the planting is new, but for the lifetime of the garden. However, I don’t recommend the use of sprinklers that soak the bark of the tree, another opener for health and disease problems. Just water the soil right where the roots are.

The best suggestion for planting under a dense tree canopy is to use resilient shade tolerant plants. If you are attempting to grow turf, use a fescue species or a shade mix (primarily contains fescue) since it is the most shade tolerant of all of the lawn grasses. You may have to have some limbs trimmed from the tree to allow extra light into the area.

Some annuals, perennials, and shrubs will grow in this environment – the best being groundcovers. English ivy, an evergreen groundcover works well but will soon grow right up the tree. Vinca minor is another evergreen that is not as invasive. Liriope and Lamium are also good perennial choices. Think of it in terms of leaf size – plants with smaller leaves require and lose less water.

The environment under a newly planted tree in full sun will change over the years. Full sun plants planted in a garden with a young maple tree are no longer appropriate once the tree has become established and more mature.

One trick of the trade is to add small amounts of compost/soil to a planting bed that has many surface roots slowly over a period of years. You should never mound soil over a root system or around the base of a tree. If you have the patience to add soil slowly, the tree roots will slowly grow into the soil but will allow for a much-improved planting medium that will more easily hold moisture.

Use these tips for successful planting under mature trees. Remember to minimize root damage so that you don’t sacrifice the health of the tree.

Parks & Forestry Division
Parks & Recreation Department
City of Upper Arlington
3600 Tremont Road
Upper Arlington, OH 43221
Phone: 614-583-5340