Tips for Planting Understory Piedmont Trees

A mature native dogwood approaching peak autumn color.

It’s that time of year again — planting time for trees, shrubs, and perennials in the southeastern Piedmont. As I’ve stated before, autumn planting gives plants time to focus on root growth while the soil is cool but unfrozen and deciduous plants don’t have to expend energy on leaf production.

I’ve offered advice on tree planting before here. But in that post, I was emphasizing issues related to trees that eventually attain canopy status. Today, my focus is on the more diminutive trees — occupants of the forest understory. Many of our native southeastern trees in this category comprise some of our better known ornamental trees: dogwoods, redbuds, sourwoods, fringe trees, Carolina silverbells, deciduous magnolias. The list is long, and depending on how you define the height of your understory, it may include large shrubs, such as our native deciduous azaleas, viburnums, and vacciniums. All of these woodies produce gorgeous flowers, most in spring through early summer.

I fully understand why Piedmonters fall in love with these beauties and want to add them to their home landscapes. And they absolutely should, but I would like to suggest that, before you plant, you consider the environmental context of the tree/shrub you want to add.

Understory trees and shrubs, by definition, dwell beneath the forest canopy giants — oaks, hickories, sycamores, ashes, beeches, maples, sweet gums, tulip poplars, pines. If you look carefully at a Piedmont forest, you’ll see that the understory dwellers grow along forest edges and within clearings, places where they have access to sunlight, but are still shielded by nearby forest giants. By growing along forest edges, smaller understory plants are protected from strong winds, and they are shaded for part of the day.

In my yard, I’ve tried to plant new understory beauties in spots where they are sheltered by canopy giants, but will still receive enough sunlight to bloom and prosper. Here in the southeastern US, our afternoon summer sun is brutal, so I’ve sited new trees so they are shaded from that searing heat by nearby larger trees. I didn’t plant the mature dogwood in the top photo, but I suspect it is thriving because it is protected from western sun by the nearby southern red oak you can just see on the left of the picture, and the mature pine trees further back.

Pine trees are especially good at protecting evergreen understory trees, like camellias, and early bloomers, like Royal Star Magnolias.  My Royal Star Magnolia is nestled beneath tall loblolly pines that protect it from harsh north winds and late freezes. Winter-blooming camellias benefit from a similar location.

Try to resist the urge to plant a single dogwood, redbud, magnolia — insert your favorite small blooming tree here — in the middle of your front lawn, where it will be bombarded by sunlight all day; shallow roots will be damaged by any chemicals (fertilizers, herbicides) you add to the lawn. And the watering regime applied to most suburban lawns will encourage shallow root growth, meaning your tree will be susceptible to toppling in strong winds and dying from drought when you can’t water.

Instead, plant your understory tree in the front of a “natural area” with larger trees. If you have no larger trees, buildings can be used the same way. Trees planted near the east- or north-facing sides of your house will be protected from the harshest winter winds and hot summer sun. Your house becomes a substitute forest canopy giant for your small tree.

Understory beauties can help each other if you plant several near each other. Create a large planting bed by removing a patch of lawn, tilling the soil to a depth of at least a foot, and adding some organic matter like decomposed leaves to create a fluffy planting bed more akin to the forest duff such plants naturally grow in. Plant your trees far enough apart to account for their eventual mature size. Don’t add any fertilizers when you plant. This only stresses the roots. Add an inch or two of organic mulch (shredded wood lasts several years) and water well.

By providing a more natural planting area and combining several plants in one space, you’ll create a much better growing environment for your additions, and the visual appearance of your landscape will be much more appealing. Also, when you group plants, you create appealing habitat for native wildlife, and as your trees mature, you’ll be able to add native wildflowers and ferns to fill in open spots.

Working with living plants is always a dynamic adventure. Every day of the year, your trees and shrubs will look different as blooms and fruits come and go, birds feed and nest, squirrels squabble, and the sun highlights different angles as it treks across the sky through the seasons.

If you provide understory trees and shrubs with what they need, the beauty you receive in return will multiply every year. Fall is for planting, and I’ll bet that almost any home landscape could be enhanced by the addition of at least one new special tree.

Get thee to a local nursery; most are holding sales. Seize this autumnal opportunity while you can!

A thirty-foot tall kousa dogwood thrives in our backyard, where the house shades it from searing afternoon summer sun.

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