Celebrating Native Trees

April 2022 marks the 150^th anniversary of Arbor Day, an ideal occasion for discussing the importance of planting trees and the reason for choosing native tree species. Join Extension Master Gardener Elaine Mills to learn details on the characteristics and attributes of 20 native trees and suggestions on their uses in the home landscape. General information on planting, care, and helpful resources will be provided.

Speaker: Elaine Mills, Extension Master Gardener
Zoom session, April 15, 2022

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Video of Presentation

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Additional Resources

Celebrating Native Trees – General Information & Resources

Trees Discussed in Presentation

Resources

Tree Species

• Video “Keystone Species of Native Plants” (Section on Woody Plants begins at 0:07:08)
• Video “Best Bets: Native Plants for Dry Conditions” (Section on Trees begins at 0:10:15)
• Video “Best Bets: Native Plants for Wet Conditions” (Section on Trees begins at 0:10:13)

Siting & Planting

• Video “Native Trees: Selecting, Planting, and Transplanting” (Siting begins at 0:43:43)
• Tree Placement on Home Grounds, University of Missouri Extension
• Tree Preservation and Replacement Guide, City of Falls Church

Tree Care

• Tree Stewards of Arlington/Alexandria (Tree care and ivy removal)
• International Society of Arboriculture (Tree care and list of arborists)
• Urban Forestry Management, City of Alexandria

Sources of Trees

• Tree Canopy Fund, EcoAction Arlington (Applications in April for fall planting)
• Small Trees Make Big Canopies Program (MGNV, Source of free trees)
• Plant NOVA Trees (Five-year local tree campaign)

Ecosystem Services of Trees

• “Celebrating Native Trees,” MGNV website, April 6, 2022
• “Climate-Conscious Gardening: Planting Trees”, MGNV website, October 20, 2021

Health Benefits of Trees

• Kuo, Ming. “How might contact with nature promote human health?” Frontiers in Psychology, August 25, 2015.
• Li, Qing. “Effect of forest bathing trips on human immune function.” Environmental Heath and Preventive Medicine, March 23, 2009.
• Robbins, Jim. “Ecopsychology: How Immersion in Nature Benefits Your Health.” Yale Environment 360, January 9, 2020.
• Ulrich, R.S. “View Through a Window May Influence Recovery from Surgery.” Science, Issue 4647, pp. 420-421
• Wolf, Kathleen L. “Urban Trees and Human Heath.” International Journal of Environmental Research and Public Health, June 18, 2020.

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Addendum: Additional Details and Answers to Chat Questions – pdf

By Elaine Mills, presenter of “Celebrating Native Trees”

04-15-2022

Chinese Weeping Willow (Salix babylonica), White Willow (S. alba), and Crack Willow (S. fragilis) are non-native species that can spread invasively from cultivation into natural areas.

• Female catkins contain numerous wind-borne seeds which germinate immediately on soil contact.
• Broken twigs of the trees can take root and colonize new areas when carried downstream, especially after floods.
• In addition, the trees’ aggressive root systems are drawn to water sources like pipes, causing problems for homeowners.

Downy Serviceberry (Amelanchier arborea) mentioned in the presentation and other Rose Family members such as crabapples (Malus genus), pears (Pyrus) and quince (Chaenomeles), can suffer from cedar-apple rust when planted near either Eastern Redcedar (Juniperus virginiana) or prostrate junipers.

• The disease requires both hosts to be present within a mile of each other.
• The results of the disease are cosmetic, making the fruit unsightly and inedible, rather than life-threatening.
• For more information on the disease, see “Cedar Apple and Related Rusts on Ornamentals” from Penn State Extension.
• The regime for preventing rust diseases is quite arduous and is not recommended by our Extension agent. See the recording of her class on “Fruit Producing Trees: Insect and Disease Management Strategies” for more information.

On the question of pruning Downy Serviceberry:

• Root suckers can easily be removed as they appear each year to maintain the plant as a single-stemmed specimen.
• If the suckers are allowed to grow, the plant will grow as a shrub rather than a tree.
• Over time, suckers will form a colony.

During the Q&A session, a question was raised regarding shorter cultivars of American Holly (Ilex opaca).

• I mentioned the female, mound-forming, shrub-height cultivar ‘Maryland Dwarf’ which grows from2 to 3 feet tall and spreads from 3 to 10 feet.
• Two female cultivars that grow 20 to 30 feet high and 10 to 15 feet wide are ‘Delia Bradley’ and ‘Greenleaf’ which are noted for their abundant fruit.
• The ‘William Hawkins’ male cultivar grows to about 15 feet at maturity, with a spread of 8 feet. It has unusually narrow and spiny evergreen foliage.

Regarding the question about American Hollies not fruiting in a woody area, Penn State Extension lists multiple factors that may affect fruit production by female trees.

• Lack of flower and fruit production may be due to poor growing conditions, such as extremely dry locations, exposure to desiccating winds, heavy shade, and poor soil drainage.
• Insect pollinators may have been scarce due to loss of habitat, use of herbicides nearby, or cold, rainy weather during bloom time.

On the question of deer-resistance of Sweetbay Magnolia (Magnolia virginiana), relatively few of the websites that provide such information list that tree species. Those that mention the tree (University of Maryland and North Carolina State University), describe it as resistant.

Regarding the expected lifespan of a Flowering Dogwood (Cornus florida):

• Bernheim Arboretum and Research Forest lists the tree’s average life expectancy at 80 years.
•  The Glen Arboretum at Towson University states that, if protected from disease and insects, the tree can live up to 125 years, with rapid growth lasting as long as 30 years.
• Care to promote a dogwood’s health includes:
  • Establishing a healthy root system, leaving plenty of space for growth
  • Mulching at a depth of 2 to 3 inches at a diameter of 10 feet around the trunk (but 6 inches away from the trunk itself)
  • Watering thoroughly and regularly in summer and fall, especially during first three years after planting
  • Providing shade in hot climates; this also helps protect from dogwood borer

Protecting trees from Yellow-Belled Sapsucker damage is a challenge. There are more than 250 species of woody plants that these birds may attack, including maple, pine, elm, apple, and dogwood. See this helpful article from North Carolina Cooperative Extension for an explanation of the problem and some suggested protective actions.

Some suggestions for distinguishing male and female trees of dioecious species when purchasing:

• Ask nurseries if they label the sex of their trees. Native-only sellers may be more likely to do this.
• Shop when the trees are in flower and look for anthers on male flowers to distinguish them from female flowers.  A problem is that young trees may not be mature enough to flower.