Wildlife in the Winter Garden

American holly (Ilex opaca).

Did you know Smithsonian Gardens joined Audubon International’s Cooperative Sanctuary Program? The goal is for the gardens and greenhouses at the Smithsonian to be designated as a Certified Audubon Cooperative Sanctuary. To become certified, Smithsonian Gardens has developed, implemented, and documented the results of an environment management plan in five key areas: site assessment and environmental planning, wildlife and habitat management, water, resource management, and outreach and education. We believe that Smithsonian Gardens has met (or in some cases exceeded) Audubon International’s environmental management standards in all five areas. We are looking forward to a site visit from an Audubon International staff member to verify Smithsonian Gardens submission.

Below is a list of plants that you can find in the Smithsonian Gardens that are native to the mid-Atlantic region and provide food and shelter to wildlife during the winter months.

• Ilex glabra, also called inkberry, is an evergreen shrub with black fruit called drupes. The fruit, attractive to birds, appears September through March. You can find this shrub in the Urban Bird Habitat Garden at the National Museum of Natural History.
• Ilex opaca, known as American holly, can be found on the south side of the Smithsonian Castle in the Enid A. Haupt Garden. This large evergreen tree provides nesting opportunities for birds and small mammals as well as bright red berries to sustain our feathered friends during the cold winter months.
• Ilex verticillata is a deciduous holly often called winterberry. Birds really seem to enjoy these beautiful berries so don’t forget that winterberries are dioecious, meaning that the berry-producing female plants need a male winterberry nearby to produce fruit. Look for Ilex verticillata on the north side of the National Air and Space Museum due east of the entrance.
• Lindera benzoin is called spicebush because of the spicy smell of the leaves when crushed.  We grow this tree for its year-round wildlife value. This tree is a host plant for the Spicebush Swallowtail butterfly and the fruit is eaten by songbirds. You can find this understory shrub in the landscape of the National Museum of the American Indian as well as in the Butterfly Habitat Garden at the Natural History Museum.
• Rhus typhina ‘Dissecta’ or staghorn sumac as it is commonly called is not only a picturesque plant but a source of reddish brown seeds that are consumed by many birds and small mammals throughout the winter months. The staghorn sumac is also a host and nectar plant for both moths and butterflies which is why you can find it in our Butterfly Habitat Garden.

Staghorn sumac (Rhus typhina ‘Dissecta’)

For more information on native plants for wildlife habitat: http://www.nps.gov/plants/pubs/chesapeake/pdf/chesapeakenatives.pdf

For more information about the Audubon International’s Cooperative Sanctuary Program:
https://www.auduboninternational.org/acsp 

–Shelley Gaskins, Smithsonian Gardens Horticulturist, Green Team Member 

Escaped from Gardens: Invasive Plant Species in the United States

This post was originally published on Smithsonian Science.

Non-native plant species pose a significant threat to the natural ecosystems of the United States. Many of these invasive plants are escapees from gardens and landscapes where they were originally planted. Purchased at local nurseries, wholesale suppliers and elsewhere, these plants have the potential of taking over large areas, affecting native plants and animals and negatively changing the ecosystem. In recent years an increase in travel and international trade has rapidly introduced many new non-native species to the United States.

“While not all non-native plants are bad, some imported species are bullies that crowd out native plants and damage the diverse ecosystems that many living things depend on,” said James Gagliardi, a horticulturist with Smithsonian Gardens.

Plants with the highest invasive potential are prolific seeders and vigorous growers which have the ability to adapt well to a variety of conditions. Native species have not evolved alongside these plants and have trouble competing. With few predators and little competition for resources, these new plants can displace native flora, reducing plant diversity until a landscape is no longer able  to support longstanding native plant, animal, and insect communities.

Here is James Gagliardi’s list of six plant invaders in the U.S. with suggestions of native stand-ins to plant in your garden:

1. Purple Loosestrife (Lythrum salicaria)

Origin: Europe and temperate Asia

(Photo by John D. Byrd, Mississippi State University, Bugwood.org)

Arrival: Purple loosestrife was introduced to the United States in the early 1800s for ornamental and medicinal uses.

Impact: Now growing invasively in most states, purple loosestrife can become the dominant plant species in wetlands. One plant can produce as many as 2 million wind-dispersed seeds per year and underground stems grow at a rate of 1 foot per year.

Native Alternatives: Blazing star (Liatris spicata), American blue vervain (Verbena hastate) and New York ironweed (Vernonia noveboracensis)

2. Japanese Honeysuckle (Lonicera japonica)

Origin: Eastern Asia

(Photo by Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org)

Arrival: One of many invasive varieties of honeysuckle in the United States, Japanese honeysuckle was brought to Long Island, NY, in 1806 for ornamental use and erosion control.

Impact: The plant has become prolific throughout much of the East Coast as it adapts to a wide range of conditions. Japanese honeysuckle is an aggressive vine that smothers, shades and girdles other competing vegetation. Many of the birds eat the fruit of this plant, thereby spreading the honeysuckle’s seeds.

Native Alternatives: Trumpet creeper (Campsis radicans) and coral honeysuckle (Lonicera sempervirens)

3. Japanese Barberry (Berberis thunbergii)
Origin: Japan

(Photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org)

Arrival: Japanese barberry was introduced to the United States in the 1800s as an ornamental. Seeds of Japanese barberry were sent from Russia to the Arnold Arboretum in 1875 as an alternative to European barberry (Berberis vulgaris), which had fallen out of favor as it was a host to Black Rust Stem—a serious fungus effecting cereal crops.

Impact: The shrub has the ability to grow in deep shade and is particularly detrimental to forest lands in the Northeast. The heavily fruiting plant forms dense thicket, crowding out native plants, and its seeds are easily spread by birds.

Native Alternatives: Shrubby St. Johnswort (Hypericum prolificum) and winterberry (Ilex verticillata)

4. Norway Maple (Acer platanoides)
Origin: Europe

(Image by Zelimir Borzan, University of Zagreb, Bugwood.org)

Arrival: The plant explorer John Bartram first introduced the Norway maple to the United States from England in 1756. The widely adaptable tree quickly became popular and was planted in towns as a shade tree and in rural communities.

Impact: The Norway maple displaces native trees and has the potential to dominate a landscape in both the Northeast and Northwest. It displaces native maples like the sugar maple and its dense canopy shades out wildflowers.

Native Alternatives: Sugar maple (Acer saccharum) and red maple (Acer rubrum)

5. English Ivy (Hedera helix)
Origin: Europe

(Photo by Chris Evans, Illinois Wildlife Action Plan, Bugwood.org)

Arrival: The introduction of English ivy dates back to the early 1700s when European colonists imported the plant as an easy-to-grow evergreen groundcover.

Impact: The planting and sale of English ivy continues in the United States even though it is one on the worst-spread invasive plants in the country due to its ability to handle widespread conditions, particularly on the east and west coasts. English ivy is an aggressive-spreading vine which can slowly kill trees by restricting light. It spreads by vegetative reproduction and by seed, which are consumed and spread by birds.

Native Alternatives: Creeping mint (Meehania cordata), Allegheny spurge (Pachysandra procumbens) and creeping phlox (Phlox stolonifera)

6. Kudzu (Pueraria montana var. lobata)
Origin: China, Japan and the Pacific islands

(Photo by Kerry Britton, USDA Forest Service, Bugwood.org)

Arrival: Japan introduced Kudzu to the U.S. at the Philadelphia Centennial Exposition in 1876. It was first promoted as an ornamental plant and later as a forage crop in the Southeast. One million acres of Kudzu were planted in the 1930s and 1940s by the Soil Conservation Service to reduce soil erosion on deforested lands. It was not until the 1950s that it was recognized as an invasive.

Impact: Once established, Kudzu grows at a rate of up to one foot a day and 60 feet annually. This vigorous vine takes over areas in the Southeast by smothering plants and kills trees by adding immense weight and girdling or toppling them.

Native Alternatives: Carolina jessamine (Gelsemium sempervirens) and Virgina creeper (Parthenocissus quinquefolia)

Smithsonian Gardens Celebrates Arbor Day 2013

This year, Smithsonian Gardens is pleased to be hosting its second annual Arbor Day Tree Planting Celebration!  Although we have a great diversity of tree species here at the Smithsonian, we are always looking to add more to diversify our collection.  There are many wonderful exotic, non-invasive species that are well-suited to the growing environment in the Washington, DC area.  However, we are currently concentrating on adding more native tree species.  This year, we have chosen two different natives to plant.

Carolina Silverbell  (Halesia tetraptera)

Carolina Silverbell is a native hardwood understory tree that is typically found along slopes and streams in ravines in hardwood forests.  They favor north and east-facing aspects with moist, well-drained acidic loam soils.  They thrive in full and partial shade and have a core range in the southern Appalachian Mountains, but stretch as far as eastern Oklahoma, northern Florida, and southern Illinois.  This tree typically grows to be 30-40 feet, but can grow as high as 80 feet.  Its primary feature is beautifully bell-shaped white flowers that hang in clusters and are borne in the spring.

A Carolina Silverbell in full bloom.

White Fringe Tree (Chionanthus virginicus)

The White Fringe Tree is another native hardwood tree that is found in its natural range which stretches from southern New Jersey to Florida, west to Texas.  The species is very variable, and no two trees seem to be alike in all characteristics.  The Fringe Tree can grow in a variety of conditions, and is cold hardy to minus 30 degrees Fahrenheit.  As with the Carolina Silverbell, this tree’s most striking feature is the flowers.  Six to eight-inch fleecy white, fragrant flowers appear in May and June and make this a beautiful addition to the landscape.

A White Fringe tree in full bloom.

On Arbor Day, Friday April 26, we will be having two tree plantings.  The White Fringe Tree will be planted at the Anacostia Community Museum, and the Carolina Silverbell will be planted at the National Museum of Air and Space, on the south side of the building adjacent to the observatory.  The Smithsonian Gardens’ Arborist and other horticulture staff will be on hand at the Air and Space event to demonstrate proper tree planting techniques and to answer questions.  The planting will take place at noon.  We hope you can join us!

-Greg Huse, Smithsonian Gardens Arborist