American Nurseryman Magazine - Horticulture Magazine and Horticulture Books - Great Groundcover Shrubs - June, 2014 - FEATURES

American Nurseryman Magazine - Horticulture Magazine and Horticulture Books - June, 2014

FEATURES

Great Groundcover Shrubs

When the space calls for drama as well as utility, woody groundcovers can provide low-maintenance, multiseason solutions.
By Susan Boss

Groundcover plants tend to be problem-solvers. Stubborn bare spots? Tricky slopes? Perennial groundcovers often are the go-to plants that help to fill in where others fall short. But what if you're designing for a space that's quite large, or you want to add more year-round interest to the garden? In this situation, rather than an herbaceous plant, a groundcover shrub may be the solution for your landscape. When choosing a groundcover shrub, you could easily be wooed by the prospect of lush blooms; does this plant have more to offer, or after flowering will it simply fade into the garden, unnoticed for the remainder of the season? Fortunately, there is an excellent range of native groundcover shrubs that rise to the challenge. Below is just a sampling of multiseason native shrubs that are easy to grow and that will readily enhance the landscape throughout the entire year.

Clethra alnifolia (summer sweet clethra) is a true garden gem, considered by many to be one of our best native shrubs. It brightens up sunny to shaded garden settings during a typically uneventful time in the garden - midsummer.

This multistemmed, upright, suckering shrub will grow 5 to 8 feet tall in full sun to part shade. It prefers soils that are moist to wet and acidic but is amazingly adaptable to a variety of conditions, including dry shade.



'Hummingbird' summer sweet clethra (Clethra alnifolia) blooms during midsummer with a profusion of white bottlebrush flowers.

Summer sweet clethra blooms during midsummer with a profusion of ascending, wandlike, white flowers that are remarkably fragrant and last up to two weeks. This deciduous shrub is late to leaf out in the spring, but it rewards gardeners with shiny, dark green leaves that turn an attractive yellow in fall.

The cultivar 'Hummingbird' flowers earlier than the species and reaches an average height of 3 feet tall, making it a particularly effective candidate for groundcover shrub use in smaller garden settings.



Southern bush honeysuckle (Diervilla sessilifolia) brings a welcome, bright shade of yellow to the quiet summer garden.
Photos courtesy of Mt. Cuba Center
Diervilla sessilifolia (southern bush honeysuckle) is another durable groundcover shrub perfect for use as a backbone for structure in the garden. This easy-to-maintain, loose, upright suckering shrub is ideal for stabilizing banks or for use in difficult situations where other plants will not grow.

Southern bush honeysuckle generally grows 2 to 5 feet tall, depending on site conditions. It tolerates dry and infertile soils, and adapts to conditions from full sun to deep shade. The new growth of southern bush honeysuckle develops a bronze cast that contrasts nicely against its shiny, deep green foliage.

Southern bush honeysuckle is considered by many to be a deer-, disease- and pest-resistant plant that will remain attractive for the entire growing season. The dense terminal clusters of many small, sulfur-yellow flowers bring welcome color to the quiet summer garden. For a more compact, uniformly upright selection, 'Butterfly' is an excellent choice that also exhibits great fall color.

Fothergilla gardenii (dwarf fothergilla) is a woody groundcover that has something to offer the garden in multiple seasons. As spring arrives, and before leaves appear, dwarf fothergilla blooms with distinctive white bottlebrush-like flowers that have a light honey fragrance.



Dwarf fothergilla (Fothergilla gardenia) blooms with distinctive white, bottlebrushlike flowers.

The bluish green leaves, similar to those of the witch-hazel, add a varying color and texture to the garden palette. Dwarf fothergilla typically reaches a height of 2 to 3 feet and will slowly colonize to carpet the ground.

It performs best in moist, well-drained, acidic soils but will tolerate drier soils with some shade. Although happy in partial shade, the best show of flowers on dwarf fothergilla develops in full sun. In the fall the foliage explodes into gorgeous shades of yellow, orange and red.

'Blue Mist' is a cultivar that was selected for its striking bluish green foliage.

Itea virginica (Virginia sweetspire) stands out from other shrubs in the garden when summer arrives and the garden seems to slow down. A graceful, arching shrub, it will mature at 4 to 6 feet tall (or taller if it is really happy) with medium to dark green leaves and lightly fragrant, white flower clusters.

Though Virginia sweetspire is naturally found in moist to wet soils from full sun to filtered shade, it is very adaptable, tolerating considerable drought and deeper shade. Virginia sweetspire is also impressive in fall as its leaves develop dazzling shades of garnet-red and purple.

This multistemmed woody groundcover with multiple seasons of interest can be admired again in the winter as snow delicately adorns its arching stems. Many cultivars are now available that offer various traits. For example, 'Henry's Garnet' has improved fall color and uniform growth and flowering, while 'Little Henry' is more compact than the species, reaching only 3 to 4.5 feet tall.



'Henry's Garnet' Virginia sweetspire (Itea virginica 'Henry's Garnet') produces lightly fragrant, white flower clusters. Fall color is an impressively rich burgundy-purple.

Rhus aromatica (fragrant sumac) is an extremely tough plant that remains attractive the entire season and is the perfect solution for hard-to-mow, steep embankments. Fragrant sumac typically grows 4 to 7 feet tall with a spread of up to 10 feet wide.

However, for smaller landscapes or refined settings, the cultivar 'Gro Low' reaches only 2 to 3 feet tall and quickly spreads to 6 to 8 feet wide. 'Gro Low' develops attractive glossy, dark green, three-parted leaves. This female form features small yellow blossoms that arrive in early spring before the leaves appear.

While this native shrub thrives in full sun and hot, dry conditions, it can handle filtered shade in the garden as well. Best of all, fragrant sumac is a showstopper in the autumn landscape with striking orange, red and purple fall color, along with hairy red fruit.



'Gro-Low' fragrant sumac (Rhus aromatica 'Gro-Low') is a showstopper in the autumn landscape with striking orange, red and purple foliage.

Xanthorhiza simplicissima (yellowroot) is an impressively adaptable woodland deciduous groundcover shrub. This multistemmed woody shrub spreads quickly to form a 2- to 3-foot tall, dense mass with its celery-like, shiny, bright green leaves in summer. In early spring yellowroot produces attractive - though admittedly inconspicuous - airy, purplish-brown flowers on its bare, leggy stems.

Yellowroot has a uniform growth habit and maintains clean foliage throughout the gardening season. It thrives in average to moist, acidic soils from full sun to part shade, but once established can handle dry shade or a wet, sunny spot.

Because it is so adaptable, yellowroot is the perfect plant for those areas of the garden where a combination of growing conditions exist. This shrub produces a spectacular display of golden yellow to orange foliage for extended weeks of enjoyment in the fall, adding to its value as a superior garden plant.

These selections are just a sampling of native, woody shrubs to complement your clients' gardens - and for solving those tricky landscape problems. They can serve an important role in filling garden voids, preventing erosion in the garden and by extending interest throughout the seasons.



Yellowroot (Xanthorhiza simplicissima) spreads quickly to form a 2- to 3-foot-tall, dense carpet of shiny bright green foliage. In fall, the shrub displays attractive yellow and burgundy color for many weeks.

Susan Boss is the Entrance Landscape Horticulturist for Mt. Cuba Center in Hockessin, Delaware, where she's responsible for overseeing the gardens along the entrance drive. She was previously a horticulturist at Winterthur Museum and Country Estate in Winterthur, Delaware. She can be reached at sboss@mtcubacenter.org.