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July 7, 2017
Native moisture-tolerant shrubs that fringe this stream in western Maryland improve the water quality and habitat for both terrestrial and aquatic fauna. Ninebark fruits are developing in the foreground, and several dogwood and viburnum species hold the white flowers peppering the shrub layer in the background. (Photo by Ryan Davis)
Not many woody plants can grow and thrive in soil that is frequently inundated, but there is a suite of native shrub species that specializes in these conditions, where even moisture-loving trees are slow to establish. These shrubs that populate wetlands and riparian (streamside) forests may not be as recognizable or charismatic as towering American sycamores that can eventually colonize very wet areas, but they are workhorses of our woods, performing incredibly valuable roles for terrestrial and aquatic ecosystems. July also happens to be the peak blooming time for many of these species, so it is the perfect month to look for and appreciate our moisture-tolerant native shrub species. The following are common shrubs in the Chesapeake Bay Watershed that fringe our streams and populate our wetlands, quietly improving our ecosystems for humans and wildlife.
Buttonbush, Cephalanthus occidentalis
Buttonbush, or button willow, is a 6-12 foot multi-stemmed shrub that has distinctive white spherical flower clusters. These develop into globes of nutlets that are important food sources for ducks and other birds. It is found throughout the watershed in moist to very wet soils, and is tolerant of a range of light conditions.
Photo Credit: Carolyn Fannon
Ninebark, Physocarpus opulifolius
Atlantic ninebark is a fast-growing, hardy shrub that is often found on streambanks but will tolerate drought and drier sites. Its exfoliating bark gives ninebark its name, and the shrub also has distinctive white flower clusters that resemble ornamental spirea. These quickly develop into pinkish-red fruit clusters which persist through the fall, providing important food for migratory and resident songbirds.
Photo Credit: R.W. Smith
Shrub Dogwoods, Cornus spp.
There are several native “shrub dogwood” species in the watershed that are tolerant of very wet and moist soils. They form dense thickets along streambanks and in ditches and wetlands, providing excellent cover for terrestrial wildlife, bearing important nectar sources for pollinators, and yielding fruit that quickly get devoured by songbirds.
Red osier dogwood, Cornus sericea, has striking autumn foliage and crimson stems that are valued in landscaping for adding winter color. Its white flowers bloom in the early summer and it bears globes of round, white berry clusters. Red osier dogwood is a larval host for the Spring Azure (Celastrina ladon) butterfly. It is tolerant of partial shade and can be found in full sun.
Gray dogwood, Cornus racemosa, has reddish young twigs and bears its white fruit on red pedicels that persist late into the winter. It is hardier than red osier dogwood, rarely being afflicted by disease or pest insects, and is also a larval host for the Spring Azure butterfly. Gray dogwood can tolerate dry sites, though it is most often found along streams, and nearly full shade, though it is typically found in open areas.
Silky dogwood, Cornus amomum, has purplish stems and bears white flowers in the early summer. Its blue fruit are borne from red pedicels in the late summer, and are important food sources for songbirds that are beginning to fatten up for migration. It is most often found in partial shade and can tolerate nearly full shade.
A thicket of Red Osier Dogwood in the winter. Photo Credit: Tom Debley
Gray Dogwood. Photo Credit: Sally and Andy Wasowski
Winterberry, Ilex verticillata
Winterberry is a holly species that is deciduous and does not have sharp, tough leaves like the well-known American holly. Like many hollies it is dioecious, meaning individual plants are either male or female. A shrub will only bear fruit if it is female and blooms at the same time that a nearby male has flowers. It bears small white flowers close to the stem that bloom throughout the summer, and produces bright red fruits that persist throughout the winter. These vibrantly colorful fruits are striking in the winter and are important food sources for resident wildlife at a scarce time of year. Winterberry is most often found in wetlands and floodplains, but can tolerate dry soil, and is broadly light tolerant and hardy to pollution. It is a larval host for the Henrys Elfin (Callophrys henrici) butterfly.
These species and other native shrubs perform valuable functions for the water bodies that they surround. Healthy riparian forests trap and filter sediments and nutrients that would decrease the water’s drinking quality and ability to support aquatic life. They also provide leaf litter which forms the foundation of the stream’s food web, supporting insects that are preyed upon by trout and other fish. Shade from trees and shrubs also cools the water down, making these streams more hospitable for brook trout and other native species. A diverse, developed shrub layer is critical to optimizing these ecosystem services; a riparian forest with only canopy trees may not be as effective as slowing water, retaining sediments, or stabilizing streambanks.
Native riparian shrubs are also critical for terrestrial animals. They support myriad native insects, again improving the foundation of the food web that supports birds and other wildlife. Their flowers are also important nectar sources for pollinator species, which allow the reproduction of a majority of flowering plants and are essential to agriculture. The fruits and buds of these shrubs are eaten by birds and larger wildlife, and many species hold fruit deep into the winter, when food is otherwise scarce. The dense patches of shrubs also provide cover that is unparalleled for escaping predators and keeping warm during the winter.
If you have a wet area or unforested stream on your property, consider planting these moisture-tolerant shrubs there to improve your water quality and habitat. Most species (especially dogwoods) can be very easily propagated by live stakes, where stems cut during the dormant season will resprout if planted in moist soil. Live stakes can be purchased from a native plant nursery or collected (with permission) from a nearby property. Plant them in a staggered 2′ x 2′ grid for a dense stand, and insert the stakes perpendicular to the slope about 75% into the soil. Once the shrubs are large enough, you can cut stakes from your own stock to spread elsewhere on your property or to give out to other conservation-minded landowners. Between the ecosystem services, beautiful flowers, and support of pollinators and songbirds, moisture-tolerant shrubs are a gift that keeps giving!
For more information, visit forestsforthebay.org or contact Ryan at firstname.lastname@example.org.
Senior Forests Projects Manager
(717) 517 8698
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