Seven Small Trees for Capitol Hill Gardens

Fringe tree (Chionanthus virginicus) blossoms are fragrant and appear just after the dogwoods.

Awake, north wind! O South wind come,

breathe upon my garden, let its spices stream out.

-Song of Songs 4:16

 

It’s time to prepare for spring, and the single most significant garden action you can take is to plant a tree. And, as designer Jan Johnson says in “Heaven is a Garden,” “while grand old trees thrill us, it is the smaller ornamental trees that unify a garden…[and] provide unparalleled seasonal interest.”

Capitol Hill gardens often have room of only one small tree and great care should be taken to match the garden with a tree in which it will thrive. This is a matchmaking process similar to adopting a dog, and if it goes well the tree will live for generations.

Seven Trees to Consider

Here are some smaller urban-friendly trees that deserve more of the spotlight than they receive. There are options for sun, for shade, and the toughest of situations. They are listed in alphabetical order by botanical name. To hear how they’re pronounced, see Fine Gardening Magazine’s web page of spoken Latin plant names: http://www.finegardening.com/pronunciation-guide/a?page=2.

  1. Aesculus pavia, Red Buckeye. This shrubby small tree is noted for its showy upright red flower clusters (panicles) appearing in spring atop dark green glossy palmate leaves (clusters of five). The flowers attract hummingbirds. This native tree which grows 10’-20’ tall, is in the horse chestnut family. It is not drought tolerant and would appreciate some afternoon shade.
  2. Amelanchier laevis, Allegheny Serviceberry or Shadbush. This multi-stem tree prefers shade to part-shade and is a modest sized (10’-20’) tree preferring acidic soil. In early spring delicate drooping clusters of white flowers appear before its new coppery glossy leaves, then small delicious berries appear in June (you’ll be lucky to get any after the birds find them). Shadbush has gorgeous scarlet fall color, if only for a long weekend.
  3. Carpinus caroliniana, American hornbeam or Ironwood. Smooth, light gray, sinewy bark is the calling card of this slender beauty. In the forest it will appear in shade together with American Beech trees, but it will also stand up to sun and French style pruning as at the Dumbarton Oaks ellipse where it functions as an aerial hedge. Small green serrated leaves turn yellow to scarlet in fall.
  4. Celtis occidentalis, Common Hackberry. In fairness, this is more of a medium sized tree, though still a candidate if you only have room for one single-stem tree in your yard. This tree’s claim to fame is its urban toughness and pollinator friendly fruits. It is the only larval host to the butterfly, Hackberry Emperor. Seeing the dark hackberries with its yellow fall foliage is stunning.
  5. Chionanthus virginicus (not retusus), Fringe tree. This drought tolerant sun loving tree is best known for its fragrant fringed white blossoms which appear after the dogwoods. The tree has a wide rounded crown so plant it where you want eye-level screening. It leafs out late, accepts a wide range of soil types, and has beautifully bright yellow autumn leaves. The native C. virginicus will support many pollinators.
  6. Crataegus viridis ‘Winter King’, Winter King Hawthorn. Another tough native happy in cities, this small drought tolerant tree offers year round visual interest to humans and great pollen and red berries for butterflies and birds. Happiest in sun, this tree has cinnamon colored exfoliating bark which shows nicely in winter, great fall color, and bright white flower clusters contrasting with spring green leaves. Winter King Hawthorn is largely spineless, another bonus.
  7. Halesia carolina, Carolina silverbell. This tree can be found in single or multi-stemmed forms. Its delicate clusters of drooping bell-shaped blossoms come at the same time as the showier dogwood, also before the leaves appear. It’s a nice tree to place where you can get close, to better appreciate its flowers, leaves, winged fruits, and golden fall color. When established, the silverbell will tolerate dry shade.

Tree Siting, Purchasing, and Planting

DIY tree planters should avoid big box stores where trees receive, at best, uneven care. Buying an already stressed tree is risky. Better to use the garden center locator on the Casey Trees web site, http://caseytrees.org/programs/planting/rebate/. When on that page, look into the $50 - $100 rebates that are likely available to cover the cost of your tree. Garden centers will have more knowledgeable staff and will be set up to handle special orders, allowing you to receive exactly the species you want.

There are many free resources on how to site and plant a tree. Here is one from the U.S. Forest Service, http://www.na.fs.fed.us/spfo/pubs/uf/plant_trees/planting_trees.htm. And remember, if you stake a new tree, which is often unnecessary; be sure to remove the stakes after one growing season to avoid the ties cutting into the tree trunk. This is called “girdling” and will kill the tree.

Before you dig a hole for your tree, you will also want to call Miss Utility, a free service that will mark the locations of underground utilities. Although you will be digging by hand, it’s best not to plant your tree directly above gas lines or other utilities which may have to be dug up in the future. Miss Utility in DC is located at http://www.missutility.net/washingtondc/.

You may wish to specify a particular tree and have it installed by qualified landscape contractors experienced with tight Capitol Hill spaces. Many advertise in these pages. If you do so, you will be able to obtain a larger specimen than you can manage on your own (these guys are stronger than us and have bigger trucks, and they’ll dig wider holes than you probably will). Hopefully your contractor will practice sound tree selection in the nursery on your behalf. Your contractor will also warrantee the tree for some period of time provided it is well cared for after planting.

Digging Deeper

Trees are fascinating organisms worth learning more about. They are the largest plants on Earth and can live for thousands of years. For a 119 page book, “The Tree Care Primer,” published by the Brooklyn Botanic Garden is an easy read and very informative. Reading it in preparation for writing this column reminded me of how good it is. See: http://shop.bbg.org/a575/the-tree-care-primer.html.

Ornamental trees planted for your personal enjoyment benefit the environment well beyond your property line. U.S. Forest Service scientists, according to one paper (https://www.itreetools.org/news/articles/PNW_scifi126_Sept2010.pdf)  “have been exploring the economic links between urban trees and a suite of environmental and social amenities, including cleaner air, moderated stormwater runoff, sequestering carbon dioxide, reduced energy consumption, and improved human health.” This research helps make the case for publicly funded green infrastructure, which is why tree rebates are available from both DC’s Riversmart Homes program and Casey Trees.

The U.S.D.A. Forest Service has created a research tool called i-Tree, now being piloted in D.C. middle schools in collaboration between the school system, Davey Tree Expert Company, and Casey Trees (https://www.itreetools.org/resources/itreelessons.php). Using special software, students will assess tree canopy cover percentage in their neighborhood, research trees’ hardiness zones, and then create a planting plan. They will calculate how much more carbon would be sequestered in their neighborhood if those trees were planted. Getting young people interested in trees is critically important. Hopefully, after their tree research is done these DC students will go outside, plant some young trees and climb some mature ones. Happy spring!

Fringe tree is often multi-stem and has a rounded crown like this example from the U.S. National Arboretum.
Red Buckeye (Aesculus pavia) has bold red upright blossoms on glossy new leaves.
Red Buckeye has a rounded habit when open grown yet can be shaped to fit Capitol Hill yards.

Cheryl Corson is a local licensed landscape architect and writer practicing on the Hill and beyond. She is responsible for dozens of trees being planted on the Hill and enjoys seeing them mature. For garden design assistance, see www.cherylcorson.com


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