The red buckeye is among the most beautiful eastern North American tree species, especially in flower, when the brilliant red panicles glow in the woodsy understory. The species occurs naturally in pinelands, pine-deciduous woods, wooded bluffs, stream banks and bottomlands throughout the range. The USDA Plants Database shows distribution in the wild from North Carolina to Florida west in an arc to West Virginia Kentucky, southern Illinois, southeast Missouri dipping into Texas. I observed numerous plants along coastal South Carolina and Mobile Bay, Alabama, growing in sandy soils. Based on the southern distribution, one could assume lack of hardiness, yet plants in gardens and arboreta survived -20°F and below. Spring Grove Arboretum, Cincinnati, OH, has many beautiful specimens that have experienced below -20°F through the years. The species is successful at the Morton Arboretum, Lisle, IL, which in the 2018-19 winter recorded -24°F. The Minnesota Landscape Arboretum, Chanhassen, MN, grows ‘Atrosanquinea’, a bright red-flowered cultivar.
The species is utilized as an understory plant in the Dirr garden, residing in the towering canopy of white oak, tupelo, and sweetgum. In this shade environment, trees are smaller and more open. Flowering is moderated a degree but still respectable. The habits of open-grown trees vary from oval-rounded to rounded, usually clothed with dense branches and large compound palmate leaves. Landscape size ranges from 15 to 25’ in height with similar spread. The National Champion (2019) was 48’ high and 37’ wide and resided in St. Louis, MO. I was asked many years past how I determined tree sizes in the Manual of Woody Landscape Plants. I typically reduced champion sizes by 50%. Not a bad rule of thumb for landscape sizes.
The foliage is beautiful, especially the early emerging leaves in riotous colors of green, purple-green, purple, yellow, orange, red, bronze and other permutations (see photo). The effect is ephemeral for the foliage soon becomes shiny dark green. Fall color is yellow at best, assuming there are persistent leaves. The anthracnose/blotch often defoliates trees by late summer. Each leaf is composed of 5 to 7, doubly serrate leaflets, to 6” long.
Flowers, pure red in the best incarnation, open with the emerging foliage in late April (Athens). They remain effective for two weeks or longer, depending on temperatures. The individual tubular flowers, 11/2 to 2’” long, are borne in a 6 to 8” long panicles at the ends of the shoots. Flowers are pollinated by the ruby-throated hummingbirds. A tree in resplendent flower is the tonic of spring. Red buckeye hybridizes with A. flava, A. glabra, and A. sylvatica, the result a mixed bag of flower colors.
The fruit is a large, smooth-skinned dehiscent capsule with one/two shiny rich brown seeds. As soon as the capsule starts to split, they should be collected and the seeds removed. Plant immediately as seeds will quickly wither. I sow seeds in 3-gallon containers filled with pine bark, cover with one-inch of bark, protect from predators, and leave outside. The root radical emerges soon after planting; the shoot the following spring. The seedlings are divided in late fall, tap root pruned, and transplanted to 3-gallon containers. The seedlings often flower in the second or third year.
Certainly, an adaptable species and can be grown in acid or high pH, sandy to clay-based soils with moderate moisture. Does show drought stress and requires supplemental water. The worse-case scenario is the leaves abscise but the tree bounces back the next year. I wish the species were more available in garden center commerce.
Aesculus pavia and A. hippocastanum hybridized in cultivation, largely without the hand of the breeder, to produce A. ×carnea, the red horsechestnut, and the cultivars ‘Briotii with deeper red flowers, ‘Fort McNair’ with lighter pink flowers and greater leaf blotch resistance, and ‘O’Neil’s Red’ with close to red flowers. ‘Briotii’ is one of Bonnie’s favorite flowering trees, consistently flowering in the garden since planting in 2013.
I have always loved the buckeyes and horsechestnuts and perhaps this small essay with inspire others to engage with the genus.
Chionanthus retusus- Chinese fringetree
Michael A. Dirr
In 2018, I was asked to assist with our county’s (Oconee, Georgia) tree planting project for a new four-lane, 3.5-mile highway. The county commissioner emphasized the concept of a tree-lined gateway to the county seat, Watkinsville. After many meetings, nursery visits and suggestions, we agreed upon 760 trees, comprising 51 different species and cultivars. The landscape architect sited the trees to minimize underwire issues, sight-line intrusion, and space allocations (medians). Locating diverse small tree species, 15 to 30’, was difficult and redbuds and dogwoods were overplanted, with more loses than I expected. One superlative addition was Chionanthus retusus, Chinese fringetree, the only regret, we did not use more. Chionanthus viriginicus, the native white fringetree, was presented in a previous HMI article/blog. It was included in the project and has prospered.
There are 60 Chionanthus species widely distributed in the tropics with only the above two species temperate zone cold hardy. Chionanthus retusus occurs in mixed forests, thickets, and along rivers in China, Korea, and possibly Japan. In cultivation, it forms a broad-rounded to spreading outline, often with long splaying shoots. I observed permutations in habit from vase-shaped to columnar (‘Tokyo Tower’). I estimate the species landscape size between 15 to 25’ high and wide. The bark on young trees is exfoliating/curling; with age and size, ridged and furrowed, the ridges flat and gray, the furrows, deep brown to black.
Foliage is 2 to 3” long, rounded in outline on ‘China Snow’; 6 to 8” long and narrow elliptic on ‘Arnold’s Pride’. Typically, deep green to glossy dark green in summer and tremendously heat and drought tolerant. Fall color, soft yellow to golden yellow, develops late (November-December), remaining effective for many weeks. The foliage is freeze resistant to at least 25°F.
The flowers are borne in 2 to 3” high, 2 to 4” wide panicles, mid to late May, Athens (zone 8). The flowers occur at the end of the new season’s shoots and shroud the canopy in a fleecy dome of snow; effective for several weeks depending on temperatures. The sexes are separate (for most part), thus fruits may or may not be present. The fruit is a dark blue, ½” long ovoid drupe, the outer covering fleshy, the inner a stone-like seed. Fruits ripen in September-October and persist longer than those of C. virginicus. Birds have stripped C. virginicus on campus while fruits of C. retusus persisted into late fall.
The species is well adapted to extremes of soil, except wet. Acid, alkaline, clay-based, and droughty (once established) are fair game. For maximum flower effect, site in full sun, yet plants in shade are effective. The species transplants readily and is available container-grown and balled and burlapped. Hardiness is open to question with zones 6 to 8 (9) suitable. I suggest -15°F will seriously injure plants, although a 30 to 35’ high specimen, grown from seed collected by E. H. Wilson, has been growing for over 100-years in Boston’s Arnold Arboretum.
The species has thrived in the highway setting and has generated questions about identity. It is an excellent under wire tree and with new cultivars available serves as an alternative to time-honored redbuds and dogwoods.
‘Arnold’s Pride’ is mentioned above. Vase-shaped outline with longer/clearer trunk and suitable for street tree use. Now in commerce and available from Pleasant Run Nursery, New Jersey.
‘China Snow’ is the thick-textured, glossy dark green leaf, profuse flowered selection developing a rounded outline with a low-branched trunk. Fits the 15 to 25’ high and wide size category. Named by don Shadow, Winchester, TN. Reasonably common in commerce.
‘Tokyo Tower’ is a more or less columnar form, slightly wider at the top, creating a narrow vase-shape silhouette. The 11-year-old plant in the Dirr garden is 24’ high and 8’ wide. Did not produce many flowers until the 6th year and then primarily in the upper branches. A superb choice where lateral space is limited.
Other cultivars include ‘Ashford’, ‘Confucius, and Spirit® (‘CRN10’).
In previous tree profiles, I discussed Magnolia acuminata and M. × soulangeana and herein highlight an increasingly important landscape species, M. viginiana. It is becoming more common in contemporary landscapes because of new cultivars with smaller sizes, increased cold hardiness, and fully evergreen foliage into zone 6 landscapes. The impetus for this discussion resulted from the August 5, 2020 visit to Apalache Nursery, Turtletown, TN. The owner, Keith Kilpatrick and his son, Taylor, have been long-time friends and native tree aficionados. The nursery nestles in a beautiful, unspoiled Brigadoon-type valley with visitors only allowed every hundred years (It was the 100th year anniversary). Bonnie commented the setting was one of the most pristine places she had ever experienced (photo). Keith and son specialize in trees and shrubs grown from wild-collected local seed. Magnolia virginiana ‘Apalache’ is their cold hardy evergreen selection, leaves lustrous dark green, clothed with branches to the ground, 20 to 25’ high. The remarkable aspect of the cultivar is the consistency of habit and foliage when grown from seed (photo, ‘Apalache’). I have grown many seedlings of the species with nothing akin to the parent. In fact, a recent seedling population derived from Keltyk® yielded small- compact and loose-open habits; tiny leaves to semi- tropical foliage (photo).
Magnolia virginiana grows in moist to wet soils, often in swamps, from Massachusetts to Florida, west to Texas, and inland to Tennessee, Oklahoma and Arkansas. In Weeks Bay Wildlife National Estuarine Research Reserve, AL, trees with trunks as large as oaks grew in the swamp next to M. grandiflora and Q. michauxii.
Landscape size is in the 30 to 50’ height range; less in width. National Champion is 115’ high and 66’ wide and resides in Jefferson, FL. Trees are single to multiple trunked, gracefully pyramidal-oval in youth, broad-oval at maturity. The foliage, bright to shiny dark green, the undersides silver-white, provide refined and billowy auras, especially when buffeted by the wind. Leaves range from 3 to 8” long, one-third to one half this in width. The deciduous types may develop pretty yellow fall color. Young stems are light green and when bruised/scraped emit a sweet lemon fragrance. Bark on large trunks is smooth, gray, and similar to beech bark.
Flowers appear in April in zone 8; a tree at the Coastal Maine Botanical Garden, Boothbay, ME, is flowering in October. Flowers develop on old and new growth of the season for several months. Each glistening white, 2 to 3” (4”) diameter, exceedingly fragrant, composed of 9 to 12 tepals (petals and sepals similar in shape and size). The knobby 2” long and wide fruits turn dark red, the red seeds emerging from the follicles on a slender silver thread. Seeds can be collected at this stage, soaked in water, the pulp removed, placed in moist medium in plastic bags, and cold stratified for 2 to 3 months. Seeds often germinate during the cold period; the white root radicles evident. Remove and transplant to suitable germination media.
The species, although native to swamps, will tolerate drier soils, especially once established. I observed chlorosis on plants in the Midwest. A pH range of 5.5 to, shouldering on 7, is suitable. Trees are produced in containers and balled and burlapped. Growth is fast, especially young seedling trees, which easily reach 6’ and more in a season. As a single specimen it develops into a pretty tree. Useful as a patio or large container element. I noticed groupings and rows of trees for screening. On the Georgia campus it has been used to shadow and soften blank-walled buildings. During nursery visits, increased production is evident as the landscape architecture profession has embraced the species for multiple uses.
Most exciting is the number of cultivars introduced in the 21st century. I have grown/observed the following.
Emerald Tower® (‘JN8’) is upright, more compact, with glossy green foliage. 20’ by 8’. Ray Jackson introduction, Tennessee.
Green Mile™ (‘MVHH’) develops a graceful pyramidal habit with long narrow shiny dark green semi-evergreen to evergreen foliage. Size 35’ by 15’. Selected by Alex Neubauer, Hidden Hollow Nursery, TN.
‘Green Shadow’ was fully evergreen after exposure to -20°F. Named by Don Shadow, Winchester, TN. 30 to 40’ high to 20’ wide.
‘Henry Hicks’ is one of the earliest hardy evergreen selections. I have grown it in the Georgia garden and although evergreen, it has been a slow mover. Estimate 30 to 40’ high; 20 to 30’ wide.
Keltyk® ( ‘MVMTF’) has smaller foliage, more compact habit and is completely evergreen, 20 to 30’ high, less in spread. I love this selection. More refined in foliage and habit. Introduced by Moon Tree Farm, GA.
Moonglow® (‘Jim Wilson’) is a larger, loose-growing selection with dark green, semi-evergreen foliage. Matures at 35 to 40’ by 15 to 18’. Survived -28°F without injury. Beautiful plant and widely available in commerce.
‘Northern Belle’ sports darker green leaves then Moonglow® and survived -35°F. 25’ high by 8 to 10’ wide.
‘Santa Rosa’ has the largest evergreen leaves of any cultivar. Selected from a Florida seed source so best in zones (6)7 to 9. More wide spreading than others. 25’ by 20’.
With the loss of Fraxinus, ash, to emerald ash borer and no resistance among the 22 U.S. native species; the uncertainty of long term performance of disease-resistant American elm cultivars; and the invasive issues attached to Norway maple and other species, new tree genetics are necessary.
I first witnessed 20 to 30’ high trees at Longwood Gardens in 2012/13 and actually begged for a few seeds. Was rejected on the basis that the species was collected in the wild from China and the host country needed to be reciprocated (assume with royalties), so could not share material. Continued sightings at the National Arboretum, Arnold Arboretum, Morris Arboretum and a west coast nursery indicated the species was being shared/distributed (without concern for reciprocity). All trees observed to date were higher than wide, similar to Tilia cordata in habit, the largest trees 35 to 40’ high. In its native habitat, trees reach 80 to 100’. I estimate 40 to 60’ by 30 to 40’ wide under cultivation.
Bark is quite remarkable, akin to that of Acer griseum, paperbark maple, exfoliating in curls and papery sheets. Colors range from light brown, copper-brown to deep chocolate-brown. Exfoliation occurs on two-year-old stems through large trunks. The tree is more beautiful in winter than in leaf.
Leaves are 2 to 4’’ long, 1 to 2’’ wide. Medium green, turning yellow in fall, shaped more like an elm leaf than the typical rounded Corylus outline. Foliage has shown high heat and drought tolerance. The summer of 2016 in Athens, GA was the hottest on record with no rain for extended periods. Two, four-year-old trees in the Dirr garden showed no foliar stress.
Flowers occur in March on naked stems; the male in drooping 2 to 4” long, reddish brown catkins; the female barely visible at the tip of the bud. Fruit is a 1/2” diameter hard-shelled, edible, globose nut held in a 2 to 4” long tubular sheath (involucre). The Morris Arboretum shared numerous nuts with the author which, 4 years later, are still germinating. I continue to manipulate the pre-germination treatments that will produce uniform percentages. Seedlings grow rapidly, 4 to 5’ in a season. Cuttings have been almost impossible to root.
To date, Japanese beetles have not been an issue (a problem on Corylus). No foliar diseases or insect damage have been observed/reported. The species is resistant to eastern filbert blight, a fungal pathogen which devastates Corylus avellana, especially ‘Contorta’, Harry Lauder’s walking-stick.
The species is cold hardy in the range of -20 to -25 F and is well adapted to zone 8, Athens-Atlanta. Trees in Chicago, IL, Boothbay, ME, Boring, OR, and Athens, GA attest to adaptability. Any well-drained soil preferably on the acid side is suitable. Trees in heavy shade are more open than those in full sun. Container-grown plants are easily transplanted.
The tree is available in commerce. Grafting and budding have been successful as has tissue culture propagation. Several vendors include Heritage Seedlings, Salem, OR and J. Frank Schmidt Nursery, Boring, OR.