As our eyes turn toward the colorful leaves this time of year, your thoughts may turn toward trees in your own yard. Do you have room — in your landscape and in your heart — for more?
Any tree may provide shade, block wind or obstruct an unwanted view, but the oak stands far above all others for its life-supporting capabilities.
Choosing one
Oaks — of the genus Quercus — support more forms of life than any other tree genus in North America. They are a critical “keystone plant.” Oaks produce acorns, which feed many mammals, birds and insects, sustaining them through the hard winter months. Less obviously, oaks support mosses, fungi, lichens and countless insects. In Pennsylvania, oaks support more than 500 species of moths and butterflies, far more than any other tree genus.
Caterpillars, in turn, are food for birds. They are essential for nestlings, which, with the exception of just a few bird groups, are unable to digest seeds. If you like birds, you may have a bird feeder. However, if you really want to help birds, especially baby songbirds, consider planting oaks. As plant numbers decline, so do insect numbers, which hurts bird populations. Native plants can help, and no native plant provides more food for wildlife than oaks.
Interestingly, there is more life in the leaf litter on the ground below an oak than there is in the tree itself. Once oak leaves finally fall, they take three years to decompose, which is much longer than other tree leaves. Fallen oak leaves thus provide a year-round home for “decomposer” organisms such as mushrooms, earthworms and nematodes. Decomposers recycle essential nutrients, including nitrogen and phosphorus, returning them to the soil for new plants to use.
Oak leaf litter also supplements the absorbent effects of oaks’ canopies and massive root systems by helping to soak up rainwater. While doing so, oak leaves purify water, filtering out pollutants from fertilizers and pesticides that would otherwise find their way into nearby streams and rivers. In addition to their usefulness for watershed management, oaks also send their roots deep, helping to stabilize soil. Also significantly, some oaks can live hundreds of years, trapping carbon that would otherwise warm the atmosphere.
Planting a tree
Plan carefully the placement of each tree you intend to plant. Consider its mature size in relation to nearby structures. Not all oaks are gigantic, and, although many are slow growers, some varieties are not. Also, consider planting more than one tree: young trees planted within 10 feet of each other will intertwine their roots as they grow, providing support during windy weather.
Both early fall and early spring are excellent times to plant trees. Planting in the fall will encourage root development long before leaves emerge and hot summer weather arrives. However, shopping for trees is easiest in the spring, when inventory is highest, including at local plant sales in April and May. Although you may be tempted to plant a large transplant for instant gratification, instead, plant small for the best outcomes. A more affordable bare-root whip will soon catch up in size to a large balled-and-burlapped transplant, growing into a much healthier tree.
Noted ecologist and oak enthusiast Douglas Tallamy suggests planting acorns because they will grow into the healthiest trees. Also, they are free, and the best time to collect them is in the fall. Trees in the white oak group germinate in the fall, whereas trees in the red oak group germinate the following spring.
Plant both acorn types about as deep as a blue jay or squirrel would in a deep pot with a mix of soil taken from the future planting site and potting mix. Keep them moist over winter by lightly watering monthly, and transplant your seedlings in the spring after their first true leaves have fully expanded. Protect your seedlings from rabbits and deer with the use of galvanized steel cages.
With more than 90 species in North America, oaks are common trees. However, their significance is uncommon. As Tallamy argues in his book, “The Nature of Oaks” (Timber Press, $28), our well-being depends on them. Therefore, plant oaks not only for wildlife, but also for the benefit of humankind. And, if you should need yet another reason to do so, plant oaks for your own entertainment. With so much life happening on and around its branches, there is never a dull moment in the life of an oak.
Where and what to get
• Audubon Center for Native Plants at Beechwood Farms Nature Reserve: Three oaks available now at aswp.org. Inventory is highest at the spring plant sale in May.
• Tree Pittsburgh: Tree adoption events are held each fall and spring; check treepittsburgh.org to register.
Best oaks for Pa.
Large trees: Northern white oak (Quercus alba), shingle oak (Q. imbricaria), bur oak (Q. macrocarpa), chestnut oak (Q. montana), pin oak (Q. palustris), Northern red oak (Q. rubra), post oak (Q. stellata), black oak (Q. velutina).
Intermediate size: Swamp white oak (Q. bicolor), scarlet oak (Q. coccinea), chinkapin oak (Q. muehlenbergii)
Small trees: bear oak (Q. ilicifolia), dwarf chinkapin oak (Q. prinoides)
Sources
“The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees” by Douglas W. Tallamy (Timber Press, $28)
“Oak Origins: From Acorns to Species and the Tree of Life” by Andrew L. Hipp (University of Chicago Press, $35)
“Spring is Tree Planting Season” by Brian Wolyniak, Penn State Extension
Maggie Tanglen is a Penn State Master Gardener. This volunteer program supports the outreach mission of Penn State Extension and provides research-based information on best practices in sustainable horticulture and environmental stewardship. For more information, contact the Penn State Extension of Allegheny County at alleghenymg@psu.edu or 412-482-3476.
First Published: October 24, 2025, 4:00 a.m.
Updated: October 24, 2025, 3:54 p.m.