Chapter 23 North American Native Alternatives to Asian Species
Biogeography is the study of where plant groups originated, how those groups migrated to where they are today, what caused them to move, and in some cases, what made them go extinct in areas where they once lived. One of the central ideas of biogeography is a particular habitat tends to have similar plant (and animal) species living there. Sometimes closely related can found in similar but widely separated locations on the planet. This happens because, at some time in the past, the now-separate habitats were connected, and one species was found throughout that habitat. When the single habitat was split up by geological forces, different groups of that one ancestral species began to change in ways that make them different species now. Still, they share ancestry, and prefer similar habitats.
Image 1 shows the regions where maple (Acer) species grow natively today. Maples first appeared in Asia around 100 million years ago, then spread to North America. Their migration path is not obvious until we rewind the clock. Image 2 shows the breakup of Pangaea and movement of the continents to their present-day positions. At the time maples appeared in Asia (late Jurassic/early Cretacous), it was part of a larger continental mass with Europe and North America. By the time the land masses separated, ancestors of modern maples were already established in all three regions. Link to original image 1; link to original image 2
By looking at biogeographic relationships we can find North American natives that are relatives of Asian species used for bonsai. For example, despite being native to different continents, North American red maples (Acer rubrum) are close cousins to two Eurasian maples: shatung maple (A. tataricum) and amur or flowering maple (A. ginnala.) All three species thrive in similar conditions, and all three adapt well to bonsai.
Another way to narrow down which North American natives might be used in place of Asian bonsai species is by looking for ecological equivalence. This principle from community ecology says that distantly related tree species can take on similar roles within an ecosystem in different geographic locations. Even though they are not related, two species occupying the same place will tend to behave the same way in cultivation. For example, Chinese dawn redwood (Metasequoia) thrives in wet lowlands and stream banks, very much like our native bald cypress (Taxodium). The two species are NOT very closely related, but do tend to behave similarly when cultivated for bonsai or for landscapes.
The distribution of major plant biomes (habitats) around the world. Similarly colored areas will have tree and shrub species that are adapted to similar growing conditions. For example, temperate broadleaf forests dominate both the eastern US, and Japan, coastal/northeast China, and the Korean peninsula. Many species that are used here for landscaping are originally from this region of Asia. Keep in mind this is a very coarse-grained map; within each biome region there will be smaller habitats where more specialized tree and shrub species are found. Link to original image.
How do these principles this help us? Suppose you want to experiment with using native tree species for bonsai. The first question is, which of our many native tree species are likely to work, and which are not? What growing conditions will they need? Which pruning and cultivating methods will work best, and which are likely to kill them? Rather than figure all this out by trial and error, we can use biogeography and ecological equivalence to provide starting points.
For example, I learned firsthand a few years back that native dogwoods do not tolerate life in a pot; they usually die if their roots are trimmed or disturbed much. If I had thought about it from a biogeographical point of view, I probably could have predicted this would happen, for three reasons. First, Asian dogwoods rarely are subjects for bonsai, which suggests they are hard to cultivate reliably. Second, even without looking up their genetic family tree, I know that Asian kousa dogwoods and our native wild dogwoods can hybridize, so they must be genetically related. Third, both the Asian and North American species live in similar habitats.
Biogeographers look at more than just genetically related species; they are interested in how unrelated species adapt to similar environments and lifestyles in different locations. Unlike maples, some of our other native tree species are found on the North American continent only. However, they live in the same general habitat and climate as an unrelated species found in Asia or Europe. If we know the natural habitat of an American native species, we may be able to find a genetically unrelated but “ecologically equivalent” Eurasian species that is used for bonsai. The training practices used for the known Eurasian species would probably be a reasonable starting point for experiments with the native American species.
So based on this theory, which American native species could be used for bonsai? I went through a couple of my guide books, picked several commonly used Eurasian species, then tried to find North American natives that either were closely genetically related (based on publicly available DNA data), or that were ecologically equivalent species. What I learned is in the first table below. It is not exhaustive or rigorously tested yet. I only offer it as a potential way to think about and perhaps simplify the process of identifying and adapting native American species for bonsai.
| Eurasian species used in bonsai | Potential N. American “equivalents” |
|---|---|
| Japanese holly, Ilex crenata | Winterberry, I. verticillata; Yaupon holly, I. vomitoria |
| Chinese hackberry, Celtis sinensis | American hackberry, C. occidentalis |
| Chinese elm, Ulmus parvifolia | Winged elm, U. alata |
| Chinese wisteria, Wisteria sinensis | American wisteria W. species; Honey locust, Gleditsia triacanthos; Black locust, Robinia pseudo-acacia |
| Chinese pea tree, Caragana arborescens | Yellow jessamine, Gelsemium sempervirens |
| Weeping willow, Salix babylonica | Black willow, Salix nigra; Swamp willow, S. caroliniana |
| Poor man’s tea, Sageretia theezans | New Jersey tea, Ceanothus americanus |
| Japanese beech, Fagus crenata | European beech, F. sylvatica; American beech, F. grandifolia; small leaved cultivars are available |
| Japanese white birch, B. platyphylla | European white birch, Betula pendula; Dwarf white birch B. nana; River birch B nigra |
| Japanese black pine, Pinus thunbergii | Pitch pine, Pinus rigida, Scrub pine, P. virginiana |
| Korean hornbeam, Carpinus turczaninowii | American hornbeam or ironwood,C. caroliniana |
| Japanese hornbeam, C. laxiflora | Hop hornbeam Ostrya virginiana |
| Satsuki azalea, Rhododendron indicum | Flame azalea, R. calendulaceum; Florida flame azalea, R. austrinum; Pink wild azalea, R. nudiflorum |
| English oak, Quercus robur | Live oak, Q. virginiana; Water oak, Q. nigra; Myrtle oak, Q. myrtifolia |
| Flowering cherry, Prunus otame | Black cherry, Prunus serotina; Choke cherry, Prunus virginiana; Carolina laurel cherry, Prunus caroliniana |
| Hinoki, false cypress, Chamaecyparis sp. | Carolina hemlock, Tsuga caroliniana |
| Oriental bittersweet Celastrus orbiculatus | American bittersweet, C. scandens |
| Japanese cedar Cryptomeria japonica | Bald cypress Taxodium distichum |
| Flowering quince Chaenomeles sp. | Crabapples, Malus sp. |
23.1 North American Native Options for Bonsai
It has come up in discussion several times at our club that people would like to have a list of North American natives that would be good for bonsai. I compiled this list from several books and commercial nursery web sites. It is not exhaustive, but is a good starting point. Many of these natives are sold by nurseries, so it is not always necessary to collect them from the wild.
| Name | Pros, Cons, Notes |
|---|---|
| Evergreens & Semi-Evergreens | |
| Pines | |
| Short-leaf pine, Pinus echinata | 2 needles/bundle, 3-4 inches, flexible but not twisted.Widely distributed across the state. Grows into a large tree with rough, purplish to brown bark. Old fields and upland woods. A major timber tree. |
| Pinyon pine, Pinus edulis | 0.8 to 1.5” needles; very slow growing in a pot. |
| Slash pine, Pinus elliottii | 2 needles/bundle, 5-8 inches, glossy dark green. Cones reddish brown, glossy, elongated. Rarely if ever seen in NC. |
| Spruce pine, Pinus glabra | 2 needles/bundle, 2 inches or more, flexible and twisting. Bark on the trunk is dark, ridged. Branch bark is smooth. Rarely seen in NC. |
| Longleaf pine, Pinus palustris | 3 needles/bundle, 9-15 inches, dusty green. Cones dull brown, 6 inches long, narrow. Young trees resemble tufts of coarse grass for up to 7 years, then rapidly gain height in central leader. Coastal plain. Needles are WAY too long for bonsai. |
| Table mountain pine, Pinus pungens | 2 needles/bundle, 1-2 inches, and stiff. Only 2-needle pine that has cones with stout prickles. Found in the NC mountains. Its 1-inch ball-shaped cones can remain on the tree for years. |
| Pitch or slash pine, Pinus rigida | 3 needles/bundle, 3-5 inches. Mostly grows in low mountains in poor soils. Forsyth County is eastern edge of its range. Only pine to back-bud easily. Grows slowly first 5 years, then 1 foot/yr. |
| Pond pine, Pinus serotina | 3 needles/bundle, 6-8 inches, flexible. Cones about as wide as long, and top-shaped. Wet, flat woods and bogs of the Coastal plain. |
| White pine, Pinus strobus | 5 needles/bundle, 3-4 inches, light green with pale line on one side. On old trunks, bark is thick & forms rectangular blocks. Western Piedmont, mountains. Dwarf cultivars are sold commercially. |
| Loblolly pine, Pinus taeda | 3 (sometimes 2) needles/bundle, 6 inches, yellow-green, not glossy. Cones 2-5 inches long, nearly as wide, and top-shaped. Widely distributed throughout Piedmont and coastal plain. |
| Pinus taeda X rigida | A naturally occurring hybrid of loblolly and pitch pine that can be found in areas where the two species overlap. Features vary between individual trees. |
| Scrub or Virginia pine, Pinus virginiana | 2 needles/bundle, 1.5 inches or less, flexible and twisting. Bark of trunk is light brownish-orange, and flakes off in thin plates. Common in poor dry soil, rocky fields of Piedmont and mountains. Tough trees. Sparse rooted, and dislikes transplanting, so not a good choice for first timers |
| Hollies | |
| Possumhaw, Ilex decidua | Leaves to 3”. Deciduous |
| Inkberry, Ilex glabra | Leaves to 2”. Deciduous |
| American holly, Ilex opaca | 2-4” leaves, dep. on cultivar. Evergreen |
| Winterberry, Ilex verticillita | Leaves to 3”. Deciduous. Needs male to pollinate |
| Yaupon holly, Ilex vomitoria | 1” leaves. Evergreen |
| Other Conifers, Evergreens | |
| Bog rosemary, Andromeda polifolia | 0.5 to 2” leaves |
| Eastern red cedar, Juniperus virginiana | Needle and scale foliage both. Slow to size up in pots |
| Bald cypress, Taxodium distichium | 0.5” needle. Deciduous. A reliable subject of bonsai |
| American arborvitae, Thuja occidentalis | Multiple cultivars available |
| Southern hemlock, Tsuga caroliniana | Fine needle or scale foliage |
| Deciduous | |
| Crabapples and Relatives | |
| Southern Crabapple, Malus angustifolia | 2” leaves |
| Sweet Crabapple, Malus coronaria | 2” leaves |
| Cottonwood, Populus deltoides | 4” leaves, surface roots |
| Quaking aspen, Populus tremuloides | 2-4” leaves. Western native |
| Washington hawthorn, Crategus phaenopyrum | 2-3” leaves. Susceptible to cedar apple rust, fire blight, quince blight |
| Cherry and Plum Relatives | |
| Chickasaw plum, Prunus angustifolia | 2” leaf. Widely available in nurseries |
| Choke cherry, Prunus virginiana | 2-4” leaf. Sometimes in nurseries |
| Red chokecherry, Aronia arbutifolia | Winter berries. Can become leggy. |
| Azaleas | The native azaleas can be hard to tell apart. In nursery trade they can be mislabeled, and colors can vary depending on variety, and whether the shrub is the original species or a cultivar. Also, they do sometimes hybridize. That said, all of them can be grown in conditions similar to satsuki azalea. |
| Alabama azalea, Rhododendron alabamense | |
| Sweet (smooth) azalea, R. arborescens | |
| Coast azalea, R. atlanticum | |
| Flame azalea, R. calendulaceum | The only species that obviously stands apart from the others. |
| Piedmont (or sweet mtn.) azalea, R. canescens | Can be found wild in Piedmont NC woodlands. |
| Swamp azalea, R. viscosum | |
| Red maple, Acer rubrum | Leaves 2-4”. Behaves like trident maple |
| Oaks | |
| Water oak, Quercus nigra | 1.5-4” leaves. Looks like live oak, but faster growing |
| Live oak, Quercus virginiana | 1.5-5” leaves. Hard to find away from coast |
| Other Deciduous Species | |
| American cane, Arundinaria tecta | Only bamboo species native to North America. Threatened in many areas |
| River birch, Betula nigra | 1-3” leaves. Easy to grow as triple-trunk |
| American hornbeam, Carpinus caroliniana | 1-3” leaves. Transplants easily |
| American hackberry, Celtis occidentalis | 2-5” leaves. Rarely seen in nurseries |
| Fringe tree, Chionanthus virginicus | 2-4” leaves. Rare in the wild, but available in nurseries |
| American smoke tree, Cotinus obavatus | Compound leaves have 1.5-3” leaflets |
| American beech, Fagus grandifolia | Leaves 3-6”, surface rooting |
| Honey locust, Gleditsia triacanthos | Compound leaves with 0.8-1.5” leaflets. Tends to have surface roots. Easy to grow from seed |
| Trumpet honeysuckle, Lonicera sempervivens | Leaves 1.5-3”. NOT same as invasive Japanese species. Red blooms |
| Black locust, Robinia pseudoacacia | 1-2” leaflets. Great masses of flowers in spring |
| Pussy willow, Salix discolor | 2-4” leaves |
| Black willow, Salix nigra | Up to 7” leaves |
| Winged elm, Ulmus alata | 1-2.5” leaves |
| Arrowwood, Viburnum dentatum | Oval 4” diameter leaves |
| Blackhaw, Viburnum prunifolium | Up to 3” leaves |
| Southern blackhaw, Viburnum rufidulum | Oval 2-4” leaves |