Oaks – Shade Trees for Sizable Areas

Four kinds of eastern North American oaks are sensible options for large landscapes like cemeteries, condominium developments, golf courses and other commercial properties. Oaks are deciduous long-lived trees that grow relatively slowly. They perform even more splendidly, as do most native plants, when cultivated within natural areas.

According to Gregory Mazur, a technical advisor for The Davey Tree Expert Company, the most commonly planted oaks in the northeast are in the following order:

• Quercus rubra (red oak),
• Quercus palustris (pin oak), and
• Quercus alba (white oak).

Quercus phellos (willow oak) may be more common in the south, says Mazur.

Quercus rubra (Northern Red Oak)

Red oaks grow quickly – two-feet-per-year over ten years – in plant hardiness growing zones 3b to 6 in full sun and moist, well-drained sandy and loamy, slightly acidic soil. Heat and drought stunt them at the extremes of zones 7/8 and growth is not as rapid or as tall as in the northern zones – 11.5-inches-per-year over nine years.

Red oaks develop chlorosis – leaves produce insufficient chlorophyll – in high pH (alkaline) soils. They do, however, withstand urban air pollution. Leaves have shallow lobes and pointed tips. They emerge pink to light red in spring, are glossy green during summer, and usually develop into ruby or russet red beacons in autumn.

Quercus palustris (Pin / Swamp Oak)

Pin oak is the most widely used and popular shade tree, according to a 1989 survey published by American Nurseryman magazine and cited by plantsman and author Michael A. Dirr (p. 827). It looks like a ramrod straight, gracious woman with a pinched-in waist, wearing a sweeping pendulous skirt. Pin oak leaves are deeply cut and pointed, lustrous green in summer, turning russet, bronze or red in autumn.

Pin oaks grow in zones 4 to 8, in full sun, and in deep, rich, acid well-drained soils. They develop chlorosis if planted in high pH (alkaline) soils. This oak is one of the fastest growing and may attain 12-15 feet over 5-to-7 years.

Quercus alba (White Oak)

White oaks grow in zones 3b to 9, and prefer full sun and deep moist well-drained and acidic soil. Growth is slow to medium – 12-to-15-feet over 10 to 12 years – then very slow after first 20 years or so. Despite attracting an impressive list of pests, white oaks are relatively long-lived. They transplant best as small, balled-and-burlapped nursery trees.

When they survive construction in woodlands, oaks grace developments with striking majesty. They are beautiful year round, considered the most handsome of oaks. Gracefully rounded narrow lobes distinguish their leaves from those of other oaks.

According to Dirr (p.815), white oaks, from a distance, appear fuzzy greenish-gray in the spring, dark green in the summer, shades of red to bronze in the autumn, and tranquil gray throughout the winter. Dirr also says that an ideal place to see the beauty of a white-oak-dominated forest is from Pisgah National Forest terrace overlook at Biltmore Estate (Ashville, NC).

Quercus phellos (Willow Oak)

Willow oaks appear fine textured because of their lance-shaped leaves and youthful pyramidal form. Summer leaves are bright or deep green; autumn leaves are yellow, bronze-orange, yellow-brown, or russet red.

They grow well in zones 5 to 9, but do best in zones 7 to 9. Willow oaks like moist, well-drained soil, but adapt to many variable soil conditions. Growth is medium, about 1-2 feet per year for about 20 years. Willow Oaks are difficult to shape to one central leader.

Sources:

• Dirr, Michael A. 1998. 5th Edition. Manual of Woody Landscape Plants: Their Identification, Ornamental Characteristics, Culture, Propagation and Uses. Stipes Publishing Co.,L.L.C., P.O. Box 526, Champaign, Ill 61824.

• USDA (United States Department of Agriculture), NRCS (Natural Resources Conservation Service). 2008. The PLANTS Database (http://plants.usda.gov, 24 August 2008). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

© Text and some photographs by Georgene A. Bramlage. 2008. Reproduction without permission prohibited.