Landscape stewardship, Step 1: Plant a native tree
6 March 2019
Lest you’re still wondering, your property really matters. Your landscape is a powerful natural resource that—with improved stewardship—can better serve you, other creatures, and the larger environment. Because the preponderance of our land is privately managed, the plants you choose to protect or introduce in your space will determine the future of our collective biodiversity.
To support birds, we must support insects. To support insects, we must provide them with plants they can eat. Trees, given their sheer size, have the most potential for feeding insects, so the first step in landscape stewardship is as simple as planting a native tree. Planting one will also jumpstart your efforts to make a positive and immediate impact for native species that are under stress from habitat loss, invasive species, and a changing climate.
Too many of our landscape trees and shrubs come from other parts of the world. Most of our birds need highly nutritious arthropod prey to raise their young, and non-native plants cannot support their reproduction. A fascinating study by Desiree Narango in the greater metropolitan area of Washington D.C. reveals that yards with mostly non-native trees and shrubs negatively affect the reproduction rate of Carolina chickadees.
Our native dogwood (Cornus florida) in spring bloom. Dogwoods host 124 species of butterflies and moths, and birds love the berries. They are not long-lived (25 years or so), but they are worth replanting or allowing to self-seed. Unfortunately, dogwoods are often replaced by Crape myrtles or other non-native trees/shrubs with little to no wildlife value. Accept no substitutes for this understory tree that has historically created a unique sense of place throughout the southern and eastern United States.
While they might look superficially pleasing to the human eye, yards with non-native trees and shrubs are poor quality habitats, and birds often choose not to nest there. Birds that do attempt nesting find fewer arthropods to feed their young and have fewer fledglings. In fact, the study shows that yards must contain 70% or greater native species to support the reproductive cycle of these chickadees. Because many birds have similar needs, it’s possible that most native bird species need a high percentage of native plants to successfully reproduce.
Human-centered preferences for non-native trees and shrubs based on aesthetic qualities or other perceived benefits like “low maintenance” or “pest free” conditions have so far left birds and other wildlife in the lurch. Armed with a new understanding of the relationship of plants and animals, we can change the composition of our private landscapes. Many steps to rejuvenating our yards lie ahead, but prioritizing planting a native tree with the greatest ecological benefit means it will have time to grow while we slowly but surely tackle other jobs like removing invasive plants and incorporating native shrubs and perennials.
A ‘Winter King’ green hawthorn (Crataegus viridis) in fruit is a sight for sore eyes in winter. This young tree was planted just a few years ago in my local park. Hawthorns feed 166 species of lepidopteran, and birds appreciate the berries and nesting habitat. It’s worth exploring the many species of this valuable genus.
Curious what tree species to plant? Consider choosing from this partial list based on a search I performed with the National Wildlife Federation’s Native Plant Finder tool online which uses entomologist Dr. Doug Tallamy’s research to generate data. Dr. Tallamy cleverly ranks trees by their ability to support wildlife as measured by their ability to host lepidopteran species—butterfly and moth caterpillars largely needed by songbirds to raise their young.
Each genus of tree below is followed by the number of lepidopteran species supported by each according to current research. I am in the mid-Atlantic region of southeastern Pennsylvania, so numbers reflect species that are supported in my area. You can do your own search based on zip code to compare. (A quick search for my Texas friends reveals quite a bit of overlap. The top 15 tree species in north Texas based on their ability to host moths and butterflies are Oak, Prunus, Willow, Hickory, Aspen/Cottonwood, Maple, Elm, Walnut, Hawthorn, Dogwood, Hackberry, Sumac, Persimmon, Juniper and Honey locust.)
Top rated tree species for the mid-Atlantic region based on their ability to host butterfly and moth species (valuable baby bird food)
Notice that tree species have differing abilities to produce bird food in the form of caterpillars. Our most valuable species are oaks for their ability to support over 500 species of moths and butterflies! The amount of bird food they produce cannot be outdone by any other plant. (Scroll down to see descriptions for options in this genus). Native cherries and plums rank next in supporting almost as many lepidopteran as the oaks…and then come willows, birches and poplars.
In choosing tree species, prioritize the most valuable species first. Plant an oak if you can…or any of the other top 20. Also keep in mind however that while the highest valued trees listed above are superb options, almost all native species provide ecological value in their own ways. Many have varied and functional roles in hosting a smaller number of specialized lepidopteran species. Others provide food for native bees or nectar for hummingbirds at critical times of the year for example. A bit of further research could flesh out more nuanced ecological contributions of each species. For example, if you are interested in supporting native bees and have assessed your space for a succession of pollen and nectar forage, you might notice that you are missing a good mid-summer source. Even though basswoods are not at the very top of the lepidoptera-hosting list, they would beautifully fill the justifiable ecological void that you’ve identified. Working together as neighbors and in communities means that we can accommodate a diversity of tree species.
Just Say No
Be careful in selecting your trees, investigating whether your chosen species is native or not. As you already know, the landscape trade sells many non-native oaks, willows, cherries, birches, maples and more. You want to choose only native varieties for their abilities to host our native insects. Non-native varieties of Norway maple (Acer platanoides) for example cannot host our insects—and are mightily invasive to boot! Japanese maples (Acer japonicum), weeping willows (Salix babylonica), ornamental cherries (Prunus avium, P. cerasus, Japanese species and hybrids), Crape myrtles, sawtooth oak (Quercus acutissima), Bradford Pear (Pyrus calleryana), Empress Tree (Paulownia tomentosa), Tree of Heaven (Ailanthus altissima), Amur cork (Phellodendron amurense)...all not native, I’m afraid.
Fear not if you have these on your property. The process of rejuvenation is slow and steady. As our awareness grows, so can our ability to change course and restore our landscapes which are often incredibly forgiving. The introduction of non-native species started long ago, and we are learning tough lessons as our historic lust for the exotic and the hardiest growing street trees is devastating growing conditions for true ecological treasures, our native trees and other plants.
Why, you ask, are such trees still available for sale if they are so damaging to the environment? Your question is good, and one that I cannot fully answer. Why are trees listed by the state and federal government as invasive species still allowed to be sold to unknowing consumers? A new committee, the Controlled Plant and Noxious Weed Committee, is now debating the topic in Pennsylvania, so I am hopeful that new and more intelligent policies will emerge to help determine which species can be grown and offered for sale.
In the meantime, the job is up to us as educated, individual consumers to demand through our purchases the plants that have an ecologically sound basis in our living environs. We as consumers have the power to change the market while we are waiting for policy to catch up with the science.
Match trees to your site
As always, assess the conditions in your yard so that your tree is well-matched for the site. Oaks, hickories, pines and poplars need sun to grow. Willows, alders and walnut like a sunny spot that is moist. Red maples, striped maples and box elders, beech and basswoods can be more shade tolerant, growing under the canopy of other trees or along a partly sunny edge. If you have not already studied the natural condition of your space, begin by observing the amount of sunlight and moisture conditions. You might also think about soil conditions and proximity to road salt or other pollutants.
Small native trees
Serviceberries (Amelanchier species) are smaller, often multi-stemmed trees with spring blooms for pollinators and delicious summer fruits for birds. There are many species, so check your area to for the hardiest selection. Shadblow serviceberry (Amelanchier canadensis) is a multi-stemmed shrub (6-20’ tall) that naturally occurs in wet areas but grows well in average soil conditions. Allegheny serviceberry (Amelanchier laevis) can take drier conditions and grows to 15-25’ depending on conditions. Downy serviceberry (Amelanchier arborea) is similar to A. laevis but can grow to 40’ tall. Apple serviceberry (Amelanchier x grandiflora) is a popular selection in the trade and is a hybrid between the previous two species. It grows 20-25’ tall. They all can have beautiful orange to red fall color and would be wonderful at the edge of the woods, in hedgerows along a fence, tucked in around taller trees, or used as specimens in smaller landscapes.
Our native American fringe tree (Chionanthus americanus) is good for smaller spaces. It hosts 10 species of moths and butterflies including the hickory horned devil and Eastern tiger swallowtail. Photo taken at Linwood Park.
If you’re considering a high-value but relatively smaller tree in the Prunus genus (our #2 most valuable wildlife genus), consider our native American plum (Prunus americana) or common chokecherry (Prunus virginiana). American plum prefers well-drained soils in sun and has a wide range across central and eastern North America. Chokecherry has a more northerly range (found in Pennsylvania and north) and is more shade tolerant and multi-stemmed. Both have a suckering habit, but unwanted suckers are easily removed. They grow 15-25’ and sport pretty, white spring blooms and nice fall color.
Stem, leaves and fruit of an American chokecherry (Prunus virginiana), a smaller native cherry tree. This botanical illustration by artist and naturalist, John Abbot visually explains why native trees are so important. Their leaves are uniquely suited to feed native insects like the small-eyed sphinx caterpillar seen here. Some of these caterpillars will grow into beautiful pollinator moths and others will become food for young song birds. Native cherries like these host 485 species of caterpillars. That’s a lot of bird food!
Image attribution: Abbot, John; Smith, James Edward [Public domain] www.biodiversitylibrary.org. Wikimedia commons.
Crabapples are also nice small trees with red fruits for the birds and leaves for insects. Trees that evolved on far-flung continents often have very different leaf chemistry, but crabapples might be an exception to this. According to entomologist Doug Tallamy, apparently our native insects can metabolize the leaves of the many native/non-native crosses that exist in the trade. In fact it’s hard to find a native crabapple species that has not crossed with other varieties, so go for it in this category.
Pawpaws (Asimina triloba) are small suckering trees that produce an almost tropical fruit. They prefer moist conditions and host the zebra swallowtail butterfly within its range. While growth is slow at first above ground, one small tree will yield a small colony in a few years. I also like them because they are shade tolerant and one of the least preferred foods for deer in my area.
Smooth sumac (Rhus glabra) along my front fence. It lends a lush, tropical look in summer and sports this amazing red-orange fall color. Plant where it has room to sucker because new stems occur readily (or trim out unwanted stems). Bluebirds love the seeds in winter, so sumac is a good winter food source for these beautiful birds. Only female plants produce seed, so plant both male and female varieties.
Red buckeyes (Aesculus pavia) are small trees (20-25’) with early, red spring blooms for the first of the migrating hummingbirds. They tend to lose their leaves early in the fall but are desirable for their smaller size and deer resistance. Native to the southeastern United States, they grow in cultivation further north to zone 4.
A specimen red buckeye (Aesculus pavia) in the United States Botanic Garden in Washington, D.C. Hummingbirds come early in the season for nectar in the bright red blooms.
The beautiful blooms of our native blackhaw viburnum (Viburnum prunifolium), one of the few native viburnums that grows to the size of a small tree, 12-15’. Native viburnums are top-ranked for wildlife value, hosting over 100 lepidoptera. Again, beware of non-native viburnums. They migrate to natural areas where they become very invasive. Photo taken in the United States Botanical Garden, Washington, D.C.
Medium-sized native trees
Great candidates for medium-sized native trees include our early blooming Eastern redbud (Cercis canadensis). The blossoms of this spring beauty provide nectar for early season bees while the leaves provide nesting material for leaf-cutter bees. They can grow in sun to shade conditions although they flower better in sun.
Eastern redbud (Cercis canadensis). They are easily tucked beneath larger trees as seen here in one of my local parks. They are also good slope stabilizers on hilly terrain. Photo taken in Linwood Park.
One of the most beautiful understory trees of the Eastern deciduous forest is our native flowering dogwood (Cornus florida) whose copious berries and buds feed the birds and butterflies and delight us with four seasons of interest.
American dogwood in my backyard woodland in fall. Young trees can easily be tucked under larger trees to mimic natural layers in the forest as seen here.
American hop hornbeam (Ostrya virginiana) and Ironwood (Carpinus caroliana) are medium-sized trees that are tolerant of part-sun, have nice fall color, and also feed numerous lepidopteran (75-96 species) and birds.
An allee of American hornbeam (Carpinus caroliniana) in the United States Botanic Garden in Washington, D.C. Shown here near full-size at maturity.
While white-barked paper birches do better up north, our own gray birch (Betula populifolia) is well adapted in the mid-Atlantic and grows quickly to develop beautiful white-gray bark of its own as it ages. It also tops out between 20-40’ and feeds hundreds of lepidopteran. Gray birch is planted in groups in the famous gardens of the High Line in New York City. Read a tribute to this great tree species here.
A young, multi-stemmed sweet bay magnolia (Magnolia virginiana) planted in the new landscaping of a non-profit organization near me. The magnolia genus supports 20 species of moths and butterflies in my area. Sweet bays will grow 10-20’ in the north and much taller further south.
Apparent in winter, the beautiful layered branching of our native blackgum (Nyssa sylvatica). This is one of our most adaptable native trees for its ability to grow in moist or dry conditions. Blackgums are long-lived (up to 400 years!) and delight with red-orange fall color. Female trees have blue fruits for the birds. They grow slowly at first putting down a deep taproot, to 30-50’. Photo taken in West Mill Creek Park.
Large native trees
If you are considering a large species, look first to oaks for their top-ranked wildlife value. Supporting over 500 species of moths and butterflies, they are bonafide work horses. Unfortunately over the years, many have been cut for their valuable wood, cleared for development, or taken down by homeowners without replanting. Some oaks are also under pressure from disease and have a hard time regenerating in woodland areas with large deer populations who kill young saplings. Check out the following list for inspiration.
Oak species in the white oak family. All need sun.
A young white oak at the Mt. Cuba Center botanical research garden in Delaware. An unbeatable shade tree for a larger space.
White Oak (Quercus alba) - Majestic. Can live for over 300 years and will reach 60-100’ tall by 50-90’ wide. If you plant a young tree, you can expect it to be about 15’ tall in 10 years and 40’ in 40 years. They are beautiful shade trees with massive branching and root systems that accommodate easy underplanting beneath the canopy if you choose. Does best on deep, well-drained soils but is adaptable. Huge growing range encompassing virtually all of the eastern U.S.
Photo attribution: By François André Michaux. Wikimedia commons.
Swamp white oak (Quercus bicolor) - Tolerates wet soils better than Q. alba but also grows well in average soil conditions under cultivation. More central to northerly range. To 60’.
Chestnut oak (Quercus montana) - A large oak for drier conditions. A tough tree found on shallow upland slopes in eastern North America to 70’.
Swamp chestnut oak (Quercus michauxii) - For large landscapes growing to 100’. Beautiful bronze-red fall color. Tolerates wetter soils than chestnut oak but otherwise similar.
Overcup oak (Quercus lyrata) - Medium-sized oak found in wet lowlands in the southern U.S. to 60’. Good park or larger landscape tree.
Bur oak (Quercus macrocarpa) - Large oak with beautiful form typically found on limestone or calcareous clay soils in the central U.S. but is tolerant of a wide variety of soil conditions in the landscape. Big leaves and acorns. To 70-80’
Chinkapin oak (Quercus muehlenbergii) - Often on dry limestone soils or rich bottomlands in central and eastern U.S. 40-50’ high in landscape conditions (larger in the wild). Nice open, rounded shape with age. Yellow to orange fall leaf color. Transplant young for best success.
Dwarf chinkapin oak (Quercus prinoides) - Smaller oak to 12’ tall or in shrub form. Can be trained as an attractive, small tree. Found on dry and rocky soils from mid-central U.S. to the eastern U.S.
“Restoring large stands of oaks to suburbia would go a long way toward shoring up the future of our nation’s biodiversity.”
Oak species in the red oak family. All need sun.
Northern red oak (Quercus rubra) - Fast growing large tree to 90’. Beautiful shade tree. One of the most widely distributed oaks in North America.
Pin oak (Quercus palustris) - Common shade and street tree with pyramidal form and red fall color. Easy to transplant. Likes acid soils - gets chlorotic if grown on calcareous soils. Grows on poorly drained clay in mid-central and eastern U.S. 60-70’ tall.
Shumard oak (Quercus shumardii) - Likes well-drained soils in southern half of the central and eastern U.S. 40-60’ tall with beautiful yellow to red fall color. Great street, park or shade tree.
Scarlet oak (Quercus coccinea) - Beautiful fall leaf color. Adaptable to moisture conditions. Occurs on dry, upland sites in the wild, but best growth reportedly occurs in moist, well-drained soils in cultivation (per. Dirr). 70’ tall. Transplant young for best success.
Southern red oak (Quercus falcata) - Lustrous, dark green leaves. Excellent heat and drought tolerance. Grows anywhere except very wet soils. Typically found on dry sandy or clay soils. Reaches northern range in PA and NJ. 70’ tall.
Black oak (Quercus velutina) - Grows in either dry uplands or in rich soils on lower slopes in central and eastern North America. Lustrous leaf surface, 50-60’ tall.
Willow oak (Quercus phellos) - Leaves that resemble willows. Naturally grows in floodplains but is known as a great street tree as well. If you live in zone 6 or south and have acidic soil, willow oaks can thrive in clay or sandy soils, and they are very tolerant of urban conditions. 40-60’ tall.
Bear oak (Quercus ilicifolia) - A smaller scrub oak for sandy or rocky sites. To 18’ tall or less. Needs an open space. Does not tolerate competition. Found throughout PA.
Shingle oak (Quercus imbricaria) - Reportedly easy to transplant and tolerates a range of soil types and pH. Popular shade tree to 50-60’ tall. Has oblong leaves unlike most other oaks. Mideastern to central U.S. but can be cultivated elsewhere.
Blackjack oak (Quercus marilandica) - Small, slow growing oak 18’-45’ tall. Grows on sandy sites with shallow soils in south central and eastern North America. Range is eastern Texas to southern PA and NJ.
A scrub oak species growing in the hills of south Dallas, Texas. An example of the tremendous diversity of oak species across the country. Photo taken at Cedar Hill State Park
Other top-ranked, large native trees
Investigate native willows (#3 on our wildlife value list) if you have a consistently moist spot in sun. Two common willows in the eastern United States are our native black willow (Salix nigra) which grows to 60’ and peach-leaf willow (Salix amygdaloides) to 12-40’. They are a good source of pollen for early season bees, and they host many showy butterflies like viceroys, commas, red-spotted purples, mourning cloaks and hairstreaks.
The knobby bark of the common hackberry (Celtis occidentalis) reminds me of home. Hackberries are tough-as-nails, medium to large-sized trees in the elm family. While they have a large range from the central to the eastern U.S., most grow on higher pH soils to 40-60’. Their narrow limb crotches support nesting birds and the persistent berries feed birds and mammals over a long season. They support 47 lepidopteran species including mourning cloaks, question marks and specialist hackberry emperor butterflies. This one sits outside my childhood home in Texas.
Explore the birches, #4 in our top-ranked list for their support of over 380 species of butterfly and moth caterpillars. In addition to hosting this high-value food for the birds, early blooms provide pollen for early season bees. River birch (Betula nigra) grows to 80’ favoring moist and sunny conditions. It’s peeling bark is familiar to us and adds character to the landscape. Gray birch as mentioned previously is a medium to large sized tree that grows quickly and develops beautiful white/gray bark with age. Black or sweet birch (Betula lenta) grows 40-60’ high and prefers moist soils but is also found on drier sites. Good for naturalizing. Twigs emit a wintergreen scent and it sports deep yellow fall color. Yellow birch (Betula alleghaniensis) is similar to black birch but is a larger tree to 60-75’. It is long lived and the most shade tolerant of the birches, generally growing in cooler environments.
River birch (Betula nigra) planted on the campus headquarters of Urban Outfitters in Philadelphia, PA. Large trees nicely pair with larger buildings, and these provide habitat in an otherwise very urban setting.
Planting size
A large investment is not necessary when adding trees to your space. Young, small trees are not only wonderful from a tactile and visual point-of-view—their lower limbs available for close inspection by all—but they generally fare better over time. Small trees will often catch up and surpass the growth of trees planted in larger sizes because their root systems have the room they need to undertake a natural progression unimpeded.
Trees grown in containers also have 100% of their roots as compared to larger, balled and burlapped trees that lose up to 80% of their root systems when dug out of the ground for transplant. The deep taproot of a young bur oak can grow 4 feet in the first growing season, so successful planting often means that trees should be young. The rooting out process for trees is very important because it helps anchor them firmly to the ground and increases their drought tolerance.
Young trees like this native dogwood (Cornus florida ‘Appalachian Spring’) are fun to watch grow. Since they often fare better over time, you can’t go wrong with planting small trees. The low, yellow-flowering ground cover in the background is our native golden ragwort (Senecio aureus). Photo taken in West Mill Creek Park
Finding your tree
Many native trees—flowering dogwoods, redbuds, hawthorns, oaks and serviceberries—are easily found in the trade. We simply must prioritize their purchase. Others like ironwoods, native cherries, willows and some birches are worth looking for despite their rarity in most nurseries. Seek out native plant nurseries or arboretum plant sales if your local nursery does not carry the selection you’re looking for. If you’re working with a landscaper, ask them to source the trees for you, and resist the temptation to accept non-native substitutes. Small trees can be bought online from bare root sources.
Skill set: Planting a tree
A simple metal cage will protect this young bur oak in my front yard from deer browse until it is older.
Most trees are planted too deeply. Getting the depth right is key to the long term survival of your tree. Locate the root flare—the point on the trunk where the uppermost roots emerge. This area where bark tissue changes to root tissue should be level with the surrounding ground soil. On mature trees, the trunk flare is visible slightly above ground as the roots enter the soil. If the trunk is buried too deeply, the trunk bark can rot, and roots will not get the oxygen they need. This shortens the life of a tree. For more information about root flares and planting depth, see this presentation by a Clemson University environmental landscape specialist.
Next, do you best to really tease apart the roots if you are planting a containerized tree, and spread them out in the planting hole (which is only as deep as the root ball). Refill the hole creating good contact between the roots and soil. After watering, mulch your tree with a layer of leaves or non-dyed mulch, and make sure that mulch does not touch the trunk. It’s hard to understand why we still see landscaping companies piling mulch against tree trunks in volcano-style fashion given that it encourages rot and girdling roots around the tree base. Watch this video by the Pennsylvania Horticultural Society Tree Tenders program for a visual experience on planting a containerized tree.
If you live in deer country, your new tree will need protection until it is 6” in diameter. Young saplings are easy deer food, and bucks will rub the bark in early winter. Simply cage your tree until it is tall enough to be out of reach.
Your landscape is a home
Our landscapes have incredible natural potential and should no longer be viewed solely as dressing to our homes. The landscape IS a home—one worth making more valuable for other creatures in the natural world. In terms of biomass, trees have the greatest ability to support wildlife. As we come to better understand the concept of healthy ecosystems, we can take steps to restore our own spaces, and the first step is as simple as planting a native tree.
Native pines are wonderful wildlife trees. The white pines (Pinus strobus) in my yard are loved by American goldfinches (seen here), chickadees, nuthatches, woodpeckers and more. They add diversity of habitat to the deciduous tree canopy and support 243 lepidopteran species in the eastern forest. Who knew that butterfly and moth caterpillars eat pine needles?! Many species specialize strictly on pine including some sphinx moths and inchworms. Doug Tallamy reported seeing bluebirds raise their first spring clutch on sawfly larvae from the white pines in his yard. How wonderful to know that our trees can be tremendous providers while entertaining us with the life they bring to our landscapes.
Sources:
Dirr, Michael A. Dirr's Encyclopedia of Trees and Shrubs. Timber Press, 2017.
Dove, Tony, and Ginger Woolridge. Essential Native Trees and Shrubs for the Eastern United States: the Guide to Creating a Sustainable Landscape. Imagine!, an Imprint of Charlesbridge, 2018.
Miller, Howard A., and Samuel H. Lamb. Oaks of North America. Naturegraph Publishers, 1985.
Narango, Desirée L., et al. “Nonnative Plants Reduce Population Growth of an Insectivorous Bird.” Proceedings of the National Academy of Sciences, vol. 115, no. 45, 2018, pp. 11549–11554., doi:10.1073/pnas.1809259115.
Sternberg, Guy. Landscaping with Native Trees: the Northeast, Midwest, Midsouth and Southwest Edition ; Guy Sternberg and Jim Wilson. Chapters Publication, 1995.
Tallamy, Douglas W. Bringing Nature Home: How You Can Sustain Wildlife with Native Plants. Timber Press, 2007.
Special thanks to the dedicated stewards of my local parks—West Mill Creek Park and Linwood Park—and to my dad, the ultimate tree planter.
