by C. Colston Burrell
Something is missing from many of today’s urban and suburban gardens – shrubs. The enduring perennial craze often blinds us to other gardenworthy plant groups, so we pack in herbaceous plants and omit a critical link. What makes a garden complete is the bridge between the herbaceous plants and the trees, which in nature is called the shrub layer. This is just one of the discernable layers in a forest, part of what ecologists call the vertical stratification of a plant community. The renewed focus on sustainable gardening provides impetus for exploring the ecological and aesthetic virtues of layered plantings, where perennials, shrubs and flowering trees are woven into a rich brocade of bark, branch, foliage and flowers.
All natural systems, whether meadow, prairie, wetland or forest, are layered or stratified, so it makes sense that gardens should be designed and planted in layers as well. In a forest or woodlot, trees form the dominant, or highest layer, called the canopy. Oaks, maples, beech and ash are common canopy trees. Below this canopy, smaller flowering trees like redbud and dogwood lower the cathedral-like roof to a more intimate level. These understory trees form the ceiling of the garden. The next level down is the shrub layer. Like walls, shrubs fill the gaps between the understory and the lowest layer, the ground plane, or herbaceous layer. This layer is composed of perennials, bulbs and grasses.
Meadows and prairies lack a tree canopy, so shrubs often form the highest layer in these ecosystems. They grow in scattered clumps like islands in a sea, creating a textural and color change. Where grassland and forest merge, shrubs create a gradual transition. They establish a visual and ecological bridge between the grasses and tall wildflowers, and edge trees like dogwood and hawthorn. This diverse edge is a dynamic place for wildlife, providing cover for feeding and nesting.
The shrub layer is the most underutilized element of the garden, though it can be one of the most beautiful and useful layers. Shrubs offer us colorful flowers, dramatic foliage, decorative fruits and provocative winter silhouettes. A garden without shrubs seems only half-dressed to my eyes and to the garden’s wild inhabitants. Shrubs furnish food and critical nesting cover to a host of birds. Larvae of the gorgeous zebra swallowtail butterfly feed exclusively on pawpaw (Asimina triloba), and many other butterflies rely on shrubs for food.
Shrubs contribute more than beauty and sustenance for wildlife, however. They form the architectural frames, or bones, that make the garden compelling in all the seasons. Like interior walls, shrubs divide and define spaces. Well placed shrubs can block or frame views, hide eyesores and direct traffic. For gardeners looking to reduce maintenance, shrubs can fill spaces once occupied by high-mai perennials that needed staking and grooming.
Winter’s bare deciduous shrubs present appealing silhouettes. The craggy branches of chokeberry (Photinia pyrifolia) or witch alder (Fothergilla gardenii) are best revealed when covered in snow. A jagged collar of oak-leaf hydrangea (Hydrangea quercifolia) leaves sets off the snowy June flowers. Flaming sumac (Rhus copallina) or chokeberry (Photinia melanocarpa) foliage enlivens the late season display. Crimson, citron and violet berries delight mockingbirds, robins and waxwings and tie-dye the somber landscape.
Broadleaf evergreens such as bayberry, rhododendron and leucothoe make a lush backdrop against which to display a beautyberry (Callicarpa americana) in full fruit or a late blooming groundsel bush (Baccharis halimifolia) that might otherwise disappear into the background. The contrast of an ascending like red twig dogwood (Cornus sericea) or winterberry holly (Ilex verticillata) against richly colored evergreens delights the eye more than a lonely specimen.
Shrubs are natural trellises to display the vines you long to grow. Train a purple leather flower (Clematis viorna) up through a viburnum and double the impact. Try scarlet honeysuckle (Lonicera sempervirens), yellow passion vine (Passiflora lutea) or carolina jessamine (Gelsemium sempervirens) to augment the gawky stems of fringetree (Chionanthus virginicus).
In flower, shrubs lift eyes so often focused downward to admire a choice trillium or delicate hepatica. With judicious selection, you can have shrubs in bloom from the earliest spicebush (Lindera benzoin) in late winter to the last witch hazel (Hamamelis virginiana) in November. The diversity of colors, shapes and scents accorded by our native shrubs is outstanding. White is the most common color. Many favorites such as viburnums, hydrangeas, witch alder and New Jersey tea (Ceanothus americanus) have white flowers. This reflective color, often accompanied by scent, aides pollinators in finding the flowers. Pink is always popular, and shrubs as diverse as the classic wild rose, the gaudy Catawba Rhododendron (Rhododendron catawbiense) and the deliciously clove scented azalea (Rhododendron prinophyllum) are sure to please. For brilliance red tubular trusses of red Buckeye (Aesculus pavia) are unsurpassed. Other red flowered beauties to excite the eye and enliven the garden include sweet shrub (Calycanthus floridus) and flaming native azaleas in shades of red, orange and yellow. Mother Nature doles out yellow in small doses. The vernal witch hazel (Hamamelis vernalis) and it autumnal cousin begin and end the season with yellow.
Look to nature as a guide for what will grow well in your area, and under what conditions of light, soil and moisture. Shrubs originate in many diverse native habitats, so success depends on matching the plant to the site. Some shrubs, particularly Ericaceous species like rhododendrons and azaleas demand acidic soil, though most others are more forgiving of pH. The majority of woodland shrubs tolerate considerable sun, while meadow species demand it. Plants from wetlands, such as winterberry holly, sweet pepperbush (Clethra alnifolia) and buttonbush (Cephalanthus occidentalis) are perfect choices for wet spots, though they thrive under ordinary garden conditions. Their wetland habitats are often dry in summer, so they are naturally adaptable. Your choices are more limited in dense shade, but maple-leaf viburnum (Viburnum acerifolium), bush honeysuckle (Diervilla species) and wild hydrangea (Hydrangea arborescens) perform admirably in the low light of mature canopy trees.
Fifteen Exceptional North American Shrubs for Central Virginia Gardens
Aesculus parviflora – Bottlebrush Buckeye
Fragrant white bottle brushes a foot high ascend like candles from the tips of every branch of this wide-spreading shrub in mid summer. Dramatic palmately divided leaves are decorative all season and turn clear yellow in autumn. Plants reach 8 feet tall with an equal or greater spread. Plant in moist, rich soil in sun or light shade. Zones 5 (4) to 8.
Photinia pyrifolia (Aronia arbutifolia) – ‘Brilliantissima’ Red Chokeberry
Decorative all season long, this rounded shrub blooms on naked stems in spring. White to pale pink flowers are followed by shiny oval leaves that turn scarlet in autumn, but not before the glossy vermillion berries ripen against the green foliage. In winter, enjoy the irregular silhouette of this 8-foot shrub. Plant in wet to dry soil in sun or partial shade. Zones 4 to 9.
Calycanthus floridus ‘Athens’ – Athens Yellow Sweetshrub
The heavenly, exotic scent of tropical fruit draws you to the spidery yellow flowers of this late spring shrub. Flowers line the slender stems in pairs before the glossy foliage expands. Plants bloom sporadically throughout the summer on plants to 6 feet tall and 8 feet wide. Plant in rich, moist soil in sun or partial shade. Zones 4 to 9
Clethra alnifolia – Sweet Pepperbush
Old spice fills the air in mid summer when the showy white spikes of this erect shrub begin to open. Elongate, quilted leaves turn yellow to tan in autumn. Plants grow to 6 feet tall and spread by runner to form clumps 10 feet wide. Plant in wet, moist or summer-dry acidic soil in sun or shade. ‘Sixteen Candles’ is a compact selection to 3 feet tall. Zones 5 (4) to 9.
Fothergilla gardenii – Witch Alder
Compact, fragrant white bottle-brush flowers open before the leaves emerge on dense compact stems. The oval, leathery leaves turn brilliant tangerine and burgundy in autumn. A tidy small shrub reaching only 3 to 5 feet at maturity, with an equal spread. Plant in rich, moist soil in sun or partial shade. Zones 5 to 8.
Hamamelis virginiana – Witch Hazel
A large gracefully arching shrub to small tree that waits until autumn to open its delicate yellow flowers that line the stems like clustered sea anemones. Plants reach 10 to 20 feet tall with an equal spread, but mature slowly. The leaves turn clear yellow before falling. Plant in rich, moist to dry soil in sun or shade. Zones 4 to 8.
Hydrangea quercifolia – Oak-Leaf Hydrangea
Dramatic sharp-lobed leaves are upstaged by the huge terminal clusters of white flowers in summer. Leaves regain prominence as they turn deep burgundy in autumn. In winter, the dried flower clusters and exfoliating bark of this 5-foot tall by 6 foot wide shrub are exceptional. Plant in moist, rich soil in sun or shade. Zones 5 to 9.
Ilex verticillata - Winterberry Holly
Scarlet berries in autumn and winter make this shrub a treasure. The small, quilted leaves clothe 5 to 10-foot stems but have little fall color. Named selections are available in a variety of sizes. You need one male to insure fruit set of this dioecious genus. Plant in rich, wet to moist soil in sun or partial shade. Zones 3 to 9.
Itea virginica – ‘Henry’s Garnet’ Virginia Sweetspire
The luscious burgundy fall foliage is reason enough to grow this small, arching shrub to 6 feet tall with equal spread. Fragrant white summer flowers in drooping terminal clusters are a bonus. Plant in wet to moist, rich soil in sun or partial shade. Zones 5 to 9.
Morella (Myrica) cerifera – Southern Waxmyrtle
The sweet, pungent scent of bayberry is found in this southern cousin of the New England favorite. The slender leaves are fully evergreen, and densely clothe the stems of this oval shrub that can reach 12 feet or more at maturity. Plants are easily pruned to control their size. Plant in moist, rich to sandy soil in full sun or light shade; protect from cold winter winds. Salt tolerant. Zones 6 to 10.
Neviusia alabamensis – Alabama Snow Wreath
A wiry shrub to 5 feet tall that spreads to form broad clumps festooned in frothy white flowers in late spring. Rhombic quilted leaves are decorative in summer and yellow in autumn. Plant in moist, rich soil in sun to light shade. Zones 4 to 8.
Rhododendron minus – Piedmont Rhododendron
A small-leaved evergreen rhododendron with soft pink to rose spring flowers long before other species bloom. The dense rounded form to 5 feet makes this shrub perfect for small gardens. Plant in rich, moist acidic soil in light to partial shade. Zones 5 to 8.
Rhododendron prunifolium – Plum-leaf Azalea
The flame of the forest is a delightful surprise in July and August, long after other azaleas have bloomed. Brilliant red to red-orange flowers grace the airy stems of this 8 to 10-foot shrub. Plant in moist, rich acidic soil in light to partial shade. Zones 5 to 8.
Rhus copallina – Winged Sumac
This small sumac, slowly growing to 8-12 feet, is fine boned and fine textured. The glossy leaves add a tropical look below branched clusters of creamy summer flowers. Unlike other sumacs, the wine-red fruit clusters are pendent. Brilliant red to burgundy fall foliage color is exceptional. Plant in moist or dry soil in sun or light shade. Zones 4 to 9.
Viburnum acerifolium - Maple-leaf Viburnum
An overlook and hard to find species with a graceful, vase-shaped form and attractive maple-shaped leaves with pink fall color. Creamy white spring flowers are followed by blue-black fruits in late summer. Plants grow slowly to 6 feet tall and wide. An exceptional shrub for small gardens, and the unique rose-pink autumn color is sure to delight. Moist to dry, rich soil in sun or shade. Zones 4 to 8.
Award winning author, landscape designer and MBG board member C. Colston Burrell has spent a lifetime studying and promoting native plants in lectures, articles and books. His book A Gardener’s Encyclopedia of Wildflowers won the 1997 American Horticulture Society Book Award. He is also author of the bestseller Perennial Combinations, 2007. Cole gardens on 10 wild acres in the Blue Ridge Mountains near Free Union, Virginia.