Flowering and Evergreen Shrubs:
An Alphabet Soup
Michael A. Dirr, Ph.D.
Copyright © 2014
Abelia―Abelia
Significant enthusiasm for A. ×grandiflora and cultivars with compact ‘RoseCreek’ among the best. ‘RoseCreek’ and ‘Canyon Creek’from my Georgia breeding program received the award of garden merit from the Royal Horticultural Society. Twist of Lime™ (‘Aghop’) with cream-yellow margined leaves is, to date, the most stable. Recently witnessed Twist of Orange™ with yellow- orange tint to the new leaves. Attractive in a container but not sure of garden performance. Twist of Lime™ held most leaves in good condition during the 2013-14 winter in our garden. ‘Kaleidoscope’, yellow/gold leaves, commands most market share. Radiance’ is a sport of ‘Kaleidoscope’ with white foliage margins. Currently, ~30 cultivars, mostly variegated, with more on the way. Genus is being taxonomically rejiggered into four genera (Abelia, Zabelia, Diabelia, Vesalea). Abelia chinensis, a parent of A. ×grandiflora, is larger in stature, with white flowers throughout summer. Hardy to Chicago. Abelia mosanensis with pretty red-budded, opening white, exceeding fragrant flowers has garnered attention. Performs better in cooler climates. Fall color is a pleasing red. Plant introductions bred ‘Golden Fleece’ and Eternal Sunshine™, the latter compact, with yellow emerging leaves, turning green and not burning in heat. Abundant white flowers and pink sepals from May to November on a 2’ by 3’ plant.
Aesculus parviflora―Bottlebrush Buckeye
Noteworthy native with adaptability from Zone 4 to 8. White, bottlebrush flowers in late spring-summer. Beautiful birch yellow fall color. Terrific shade tolerant shrub. No significant breeding with buckeyes. Attempted to hybridize red buckeye, A. pavia, with A. parviflora to produce a pink-flowered bottlebrush.
Berberis―Barberries
Invasiveness has tempered enthusiasm for this species. Still numerous NEW introductions with ‘Admiration’ with red-purple centers and cream to yellow margins on a compact framework, quite eye-catching. ‘Daybreak’ is a yellow leaf selection with excellent heat tolerance and orange fall color. Yet to set seed. From
Red and yellow leaf cultivars are so abundant and indistinguishable that it is difficult to pin-point the best. Spring Meadow has many new introductions in 2013.
University of Connecticut evaluated cultivars for fruit production. Lowest seed per plant: ‘Kelleris’ (6), ‘Aurea’ (5), ‘Bagatelle’ (2), ‘Antares’ (1), Crimson Ruby™ (0), and ‘Golden Devine’ (0). Continued evaluation showed all produce fruit. Sparkle had 35,300 fruits.
Buddleia davidii―Butterfly-bush
In and out of garden fashion like neckties. Resurgence with new colors, rose-red - ‘Miss Ruby’, ‘Miss Molly’; compactness – ‘Blue Chip’, ‘Lilac Chip’, ‘Pink C hip’; and total sterility - ‘Asian Moon’. Trials at RHS Wisley, England, reflected visitors’ penchant for flower colors approaching red with ‘Miss Ruby’ top vote collector.
Buzz™ Series from Thompson & Morgan are compact, 3 to 5’ high and wide. Flutterby™ Series from Ball Horticultural umbrellas ~15 cultivars. I consider ‘Blue Heaven’ among the best.
My Georgia program introduced eleven with ‘Attraction’ (red-purple), ‘Guinevere’ (deep purple), and ‘Bicolor’ (lavender with butterscotch eye) the most popular.
Plant introductions and Bailey Nurseries will introduce Funky Fuchsia™, rose –red; Groovy Grape™, vibrant purple, and Psychedelic Sky™, restrained blue, in 2014 through First Editions®. All have been in the Dirr garden for two years and are terrific performers.
Noted a double-flowered, violet-purple hybrid that had the appearance of a double- flowered African violet. First double I have observed. From Peter Moore, England.
Sterility is a large issue with Oregon banning cultivars that produce greater than 2% viable seed.
Excellent web site, with history, breeding and garden notes on the genus. The author is a chemistry professor with an unbelievable passion for Buddleia.
Buxus―Boxwood
Voted number one shrub in a survey of 4,000 landscape professionals. See Nursery Management 27(8):2011. All are green, some blue-green, functional, utilitarian, deer-resistant, broadleaf evergreen shrubs. Observed no browsing in an Athens cemetery that is over-run with boxwood and deer. Boxwood blight has created a stir. Currently, the U. S. National Arboretum is assessing blight resistance and actively breeding for resistance. There is considerable screening research in progress at North CarolinaStateUniversity. What makes Buxus a fascinating landscape plant is its adaptability from Maine to Florida. If it were taken out of the landscape equation, there would be an unfillable void.
Callicarpa―Beautyberry
Numerous species known for metallic purple-colored fruits in fall. Energetic breeding by Dr. John Ruter and Dr. Ryan Contraras, but nothing new materialized. Callicarpa dichotoma may be the most cold hardy. All flower on new growth. ‘Duet’ is a cream-margined, medium-green centered leaf, white-fruited selection that seldom reverts and does not scorch in sun/heat. ‘Early Amethyst’ and ‘Issai’ fruit abundantly. Treat as cut-back shrub to stimulate vigorous shoot growth.Callicarpa kwantungensis, with reddish purple new growth and purple fruits has become available in the market.
Calycanthus―Sweetshrub
Great native (C. floridus) with sweet fragrance to flowers. Select ‘Michael Lindsey’, ‘Edith Wilder’, ‘Athens’ (yellow) for guaranteed fragrance. Hybrids from North CarolinaState include ‘Hartlage Wine’ (3 to 3 ½”, red-maroon flowers), ‘Aphrodite’ (similar but fragrant; although plant in Dirr garden had no fragrance), and Venus™ (white, akin to star magnolia). They embody the native species and C. chinensis, the Chinese species, with large, white tinged pink, non-fragrant flowers. These hybrids are block-buster shrubs in flower! Venus™ is fickle with petal spot and short-circuited life span (Dirr experience).
Caryopteris―Blue-mist Shrub
Overrun with cultivars but a worthy choice in sandy, well-drained soils, full sun exposure, for summer into fall blue flowers. Flowers on new growth and has been hardy as a subshrub at the ChicagoBotanic Garden. Many yellow leaf and white-margined variegated cultivars. ‘First Choice’ maintained erect, compact habit, deep blue flowers, and best foliage in Georgia trials. ‘Kew Blue’ and ‘Longwood Blue’ are worthy.Yellow foliage cultivars lose intensity in heat of southeast. Certainly better in the north.
Ceanothus ×delileanus, C. ×pallidus
Blue and pink flowers on compact plants from old and new wood. Typically summer flowering. ‘Henri Desfosse’ (blue), ‘Gloire de Versailles’ (powder blue), and ‘Marie Simon’ (pink) prospered in Georgia trials. Most are West Coast, Mexican species, but the above hybrids incorporate C. americanus and C. herbaceus. Terrific breeding opportunities in this genus. Adaptable to Boston. Ceanothus americanus, New Jersey Tea, is a remarkably disease-resistant, summer white flowering, 3 to 4’ high native with adaptability from Zone 4 to 8.
Cephalotaxus―Plum-yew
Important Taxus, yew, alternatives where deer are problematic. Long dark green needles separate them from Taxus. Cold (Zone 6) and heat tolerance (Zone 8-9), deer resistance, and shade tolerance are attributes. Many cultivars with ‘DukeGardens’,‘Norris Johnson’, and ‘Prostrata’ leading the pack.
Chaenomeles―Floweringquince
Who cares? Old-fashioned, antiquated, creaky shrubs. Refreshing in winter-early spring in myriad colors on naked stems. Dr. Tom Ranney introduced ‘Scarlet Storm’, ‘Pink Storm’, and ‘Orange Storm’, all with 1 ¾ to 2 ½” diameter, double flowers, fruitless, and thornless. Observed abundant fruit on ‘Scarlet Storm’ in Oregon. New and time will arbitrate their greatness. Estimated to 6’ high. Noticed leaves present in good condition in November (Athens) which is not the norm for C. speciosa. At PII, sprawling habit in containers although advertised as upright.
Clethra alnifolia―Summersweet
Nifty native from Maine to Florida and Texas in moist to wet habitats. White, pink, to rose-red, spicily fragrant flowers in summer. ‘Compacta’, ‘Sixteen Candles’, ‘Ruby Spice’ among the best. Sugartina® (‘Crystalina’) and Vanilla Spice™ (‘Caleb’) are newer white-flowered selections. Growing both and not particularly impressed. Larger than advertised. Both over 5’ in Plant Introduction’s trials. Hybrid of ‘Hummingbird’ and ‘Ruby Spice’ with yellow-orange new growth maturing to glossy dark green is intriguing. Has yet to flower. Perhaps in 2014.
Cornus amomum―Silky Dogwood
Cornus sanguinea―Bloodtwig Dogwood
Shrubby, stoloniferous to clump-forming rather aggressive shrubs. Discovered a red-stemmed form of the typical purplish brown species C. amomum. Excellent orange-red fall color in 2011. Cornus amomum is native to most of the eastern U.S. and grows into Florida. This red-stemmed selection allows for successful culture in the South (and North) where canker is a problem on C. alba and C. sericea.
Several yellow-orange-red stemmed C. sanguinea cultivars including ‘Anny’, Arctic Sun™ (‘Cato’), ‘Midwinter Fire’, etc. Beautiful in the winter landscape.
Cornus mas--Corneliancherry Dogwood
Cornus officinalis--Japanese Cornel Dogwood
Pretty yellow flowers appear on naked branches in March-April, sometimes as early as February. C. officinalis flowers before C. mas yet the red fruits mature later in summer. Many cultivars of the latter with ‘Aurea’, yellow foliage, and ‘Variegata’, white-margined leaves, among the prettiest. ‘Kintoki’ is a prolific flowering selection of c. officinalis. The fruits of C. mas are used in syrups, preserves and jellies particularly in eastern European countries. Numerous cultivars have been selected for fruit qualities.
Corylopsis―Winterhazel
Delightful yellow-tasseled flowers on naked stems dance to the yawning of a long winter. No cultivar glut here but the species C. glabrescens, C. pauciflora, and C. spicata are all worthy. ‘Gold Spring’ (‘Golden Spring’) is a yellow leaf type of C. spicata. Needs shade in the South. Have a compact, blue-foliage, soft yellow flower selection at PII.
Corylus―Filbert
‘Red Majestic’ and ‘Red Dragon’ with contorted stems and red-purple leaves provide year-round interest. ‘Red Magic’ leaves turn green quickly. ‘Red Dragon’ displays complete resistance to eastern filbert blight; 10 to 12’ by 6 to 8’. The latter hybridized at OregonStateUniversity.
Cotinus coggygria―Smokebush
Have yet to add the species to the Dirr garden but am impressed with ‘Daydream’, ‘Dusky Maiden’, and ‘Young Lady’. “Smoke” on the first and third smother the foliage. The middle has a wavy-surfaced, bronze-purple leaf, smaller stature and resulted from C. szechuanensis × ‘Velvet Cloak’.
Cryptomeria japonica―Japanese Cryptomeria
Many compact forms with Chapel View™, ‘Globosa Nana’, and ‘Gyokurya’ among the best. Chapel View™ is derived from a witches-broom discovered at DukeUniversity on a large ‘Yoshino’. Compact tear-drop shape and green winter color without the pronounced browning that occurs on ‘Globosa Nana’ and others.
Daphne―Daphne
All are potentially wonderful, if they live! Fan of D. genkwa, Lilac Daphne, with lilac-colored flowers. Unfortunately, not fragrant. Daphne ×transatlantica produces white, fragrant flowers throughout summer. Hardy in Maine (Boothbay); performing well in Athens. Daphne odora is the best choice for the South.
Diervilla―Bush-honeysuckle
A rather obscure native shrub with smallish yellow flowers in summer, bronze young shoots, deep green at maturity, yellow to reddish in autumn. Principle asset is durability. Have grown countless seedlings with several added to garden. Bonnie always . . . why? Cool Splash™ is a white-margined, green-centered leaf selection. Holds variegation in heat. Prone to reversion. Diervilla has been hybridized with Weigela.
Distylium―Isu Tree
Evergreen members of Hamamelidaceae with small red flowers in mid winter-early spring. Zone 6 adaptability with D. racemosum. ‘Blue Cascade’, ‘Emerald Heights’, and ‘Vintage Jade’ are hybrids of D. racemosum and D. myricoides. ‘Vintage Jade’ grew 2’ by 5’ in 6 years and is being successfully grown in Louisville, KY. Superb alternatives to cherrylaurels, hollies, and junipers. See for in-depth information. New introduction is Coppertone™ with bronze-purple new growth, maturing to matt blue-green. Stunning when new leaves are emerging. Estimate 2-3’ by 4-5’. Linebacker™ is an upright, broad columnar form with reddish purple new shoots. Will reach 6 to 10’ by 4 to 6’. Both are Plant Introductions hybrids. Distylium ‘Spring Frost’ has white young shoots that mature to green. Introduced by Greenleaf Nursery in Garden Debut™ program.
Euonymus alatus―Winged Euonymus
Great red fall coloring shrub but invasive and listed as such in 21 states. Banned in Massachusetts and New Hampshire. Yi Li, University of Connecticut, developed a sterile triploid from endosperm tissue of ‘Compactus’. Not yet on market but a major advancement when commercialized, if truly fruitless. According to the research appear, ~about 8 to 10 plants have been recovered from the 3n endosperm tissue. I have observed that not all triploid plants are sterile.
Fothergilla ×intermedia
Hybrids between F. gardenii and F. major are designated as such. ‘Mt. Airy’, introduced by the author, gave Fothergilla an identity. Still the most common cultivar in commerce because of reliable flower production and consistent yellow-orange-red fall color. ‘Blue Shadow’ from Gary Handy, has glaucous blue leaves and is a sport of ‘Mt. Airy’. Beautiful summer foliage and similar flowers and fall color to ‘Mt. Airy’.
×Gordlinia grandiflora
Remarkable semi-evergreen hybrid between Franklinia and Gordonia engineered by Dr. Tom Ranney. Flowers, 3 to 4” across, open on new growth in summer-fall. Older leaves turn brilliant red (purple). Shrub or small tree. Exceedingly fast, 5’ in a single season at PII. Easy to root from cuttings. Requires excellent drainage and a degree of good cultural fortune. Estimate Zone 6 to 8.
Gardenia jasminoides―Gardenia
Worked on cold-hardy (Zone 6) breeding with Pinwheel™, a single, white, fragrant, 3’ by 3’, performing well in Louisville. By degrees, the hardiest gardenia to date. Heaven Scent™ is smaller in all characteristics and slightly less cold hardy than Pinwheel™. Both with single, 6-petaled flowers in May-June, reblooming into fall. Breeding continues with a cold-hardy, double-flowered reblooming selection, ‘Doublemint’, from PII, that flowers into November. Trying to breed a pink flowered gardenia.
Hamamelis―Witchhazel
First order shrubs offering kaleidoscopic flowers from fall into late winter, brilliant fall colors, and ironclad adaptability. ‘Wisley Supreme’, H. mollis type, with sweet-scented, yellow flowers and spectacular yellow fall color is a beacon in the new Dirr garden. Numerous H. ×intermedia cultivars. Consider the native H. virginiana, with fragrant spidery yellow petals in fall and rich birch yellow fall color. This species grows almost anywhere. ‘Lemon Lime’ has leaves speckled yellow, light green, and green; delicately beautiful. Holds variegation in shade. ‘Harvest Moon’ and ‘Little Suzie’, 5’ by 5’, are worthy. New species. H. ovalis, discovered in Mississippi, is stoloniferous with floral characteristics similar to h. vernalis.
Hibiscus syriacus―Rose-of-Sharon
Too many. Most so-so. Chiffon™ and Satin™ Series have merit. Impressed with Blue Satin™ (‘Marina’), a deep velvety blue-purple with red-maroon center. Species is back in fashion. Doug Welty, who handles plant sourcing for QVC(TV), could sell 300,000/year. Everybody has new cultivars. Need compact habits, a range of flower colors and sterility. See Bailey Nursery Spring Meadow and Greenleaf Nursery for a cornucopia of new introductions.
Hydrangea (see separate handout; continually updated; estimate more new Hydrangea introductions than for any other genus)
Hypericum―St. Johnswort
Four-hundred species. I’m confused. Believe the U.S. natives are worthy. Love H. densiflorum as it grows in water (mountain tops also) with rich deep green, linear, fine-textured leaves that turn yellow-orange in fall. Hypericum frondosum ‘Sunburst’ produces 2” diameter bright yellow flowers contrasted with the blue-green foliage. Hypericum kalmianum Blue Velvet™ with smaller ¾” diameter flowers and glaucous blue foliage is worthy. At PII, Hypericum breeding is in high gear, with seedling selections of Blue Velvet™ more compact and richer glaucous blue in foliage. Cobalt-n-Gold™ is the first introduction from pii’s breeding.
Illicium―Anise
Fragrant foliage, shade tolerance, deer and pest resistance have endeared these evergreen shrubs to Zone (6)7 to 9 gardeners. Illicium parviflorum ‘Florida Sunshine’ sports soft yellow leaves. Plant Introductions has a new compact selection, similar to ‘Florida Sunshine’ in leaf color but easier to root, grow and not as wild and woolly. New purple leaf type, ‘Purple Haze’, I. anisatum, increases the color palette. ‘Pink Frost’ has white-margined leaves that turn pink-rose in cold weather. A selection of I. floridanum.
Indigofera decora―Chinese Indigo
The genus is immense with as many as 700 species. This species grows 1 to 2’ high, spreading by rhizomes/stolons to form large colonies. Pretty blue-green leaves, pink-rose flowers in 4 to 8” long slender, arching-pendulous racemes. Flowers profuse in May; still chugging along in October. In the new Dirr garden, this plant is subject to frequent queries. Indigofera kirilowii grows slightly taller (3’) with bright pink flowers. Both flower on old and new wood. Estimate Zone 5 to 7.