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 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 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 Achieves Museum Accreditation

AAM Accreditation

On March 11, 2013, Smithsonian Gardens received accreditation from the American Alliance of Museums (AAM), a designation that confers a high mark of distinction for a museum. Accreditation signifies excellence to the general public as well as to the greater museum community, the public garden community, and other cultural organizations.

Smithsonian Gardens (SG) began the accreditation process in 2007 by undertaking an Institutional Assessment through AAM’s Museum Assessment Program (MAP). The assessment provided an overview of Smithsonian Gardens’ entire management and operational practices and involved three distinct phases—self-study, peer review, and implementation. Using the outcomes of the MAP assessment, Smithsonian Gardens launched an intensive strategic planning process which resulted in an organizational name change (it had formerly been known as Horticulture Services Division) and a refined mission.

Armed with SG’s FY2010-2015 Strategic Plan http://www.gardens.si.edu/about-us/docs/SmithsonianGardens-Plan.pdf , Smithsonian Gardens undertook the AAM accreditation process in 2010.   To earn accreditation a museum first must conduct a year of self-study and then host a site visit by a two-person team of peers. AAM’s Accreditation Commission, an autonomous body of museum professionals, considers both the self-study and site visit report to determine whether a museum should receive accreditation.

Of the nation’s 17,500 museums, only 1,000 are currently accredited, and only 3% of the latter are public gardens. In the D.C. metro area only two other public gardens have attained accreditation status: the United States Botanic Garden (www.usbg.gov) and Green Spring Gardens (www.fairfaxcounty.gov/parks/greenspring).

Accreditation recognizes high standards in individual museums and ensures that museums uphold their public trust obligations. Developed and sustained by museum professionals for over 40 years, AAM’s museum accreditation program is the field’s primary vehicle for quality assurance, self-regulation and public accountability.

AAM’s Characteristics of Excellence are the standards by which all museums can and should strive to achieve in ways appropriate to their resources. To best serve their communities, it is essential that museums be committed to institutional improvement and maintaining the highest standards in collections stewardship, governance, institutional planning, ethics, education and interpretation, and risk management. AAM accreditation signifies excellence and accountability to the entire museum community, to outside agencies and to the museum-going public.

For more information about the American Alliance of Museums and its Accreditation Program, including a complete list of accredited museums, please visit www.aam-us.org .

Join us for Earth Matters to Smithsonian Gardens – Garden Fest 2013!

In celebration of National Public Gardens Day, join us on Friday for Earth Matters to Smithsonian Gardens – Garden Fest 2013!  This year’s Garden Fest is inspired by the National Museum of African Art’s exhibition, Earth Matters:  Land as Material and Metaphor in the Arts of Africa.

At Earth Matters to Smithsonian Gardens – Garden Fest 2013!, visitors of all ages can participate in fun and lively activities focused on interacting with the earth.  Help create an ephemeral land art installation with materials from the many Smithsonian Gardens with artist Emily C-D, listen to live music, make a seed bomb, journey on an ancient expedition with the help of petrified wood, fossils, amber, and gardens tools, or dance Zumba!  Smithsonian Gardens will also hold a plant container design contest, host a photo shoot for our Shutter-Bug Collection on Pinterest, and offer informal workshops on composting.  There will be demonstrations highlighting the connection between Smithsonian Gardens’ irrigation plan and the Smithsonian weather station, and learn about the many tomato varieties that are grown in Smithsonian Gardens’ Victory Garden.

Stop by during your lunch break or after work to hear great live music, for a snack or drink at the Castle Café (featuring a special garden menu for the event), view the Earth Matters exhibit in the gardens and at the National Museum of African Art – both open until 7pm – and have some fun in the garden at Garden Fest!

DETAILS:
Date: May 10th, 2013
Time: 11 am to 7:00 pm
Location: Enid A. Haupt Garden behind the Smithsonian Castle
Metro: Green/Yellow or Blue/Orange lines to L’Enfant Plaza or Blue/Orange line to Smithsonian
FREE!

Watering Well: Irrigation Tips for Your Garden

Now as summer approaches we anticipate getting back into the garden and tending to the lawn. There is one element of gardening that should not be overlooked and that is getting your irrigation system tuned up for the season. Fully automated irrigation systems afford gardeners the convenience of not having to drag water hoses all over their property.

Sean Jones, Folger Rose Garden. Smithsonian Gardens.

Energize your system’s mainline slowly and check the grounds for wet areas. This is a good way to find any leaks in your mainline and repair them before money has been wasted on an undetected leak. Here are a few easy things you can do to ensure that your system is in proper working order which can also save you time and money:

• Check the irrigation timer and adjust any previous programs that may have been input from last season as necessary. With seasonal changes come programming changes. Your plants’ water requirements are going to differ from what they were in the fall when you winterized your system. You might actually use a lot less water at the beginning of the season which can translate directly into savings on your water bill.
• Once you have done these things, run each individual zone and check for coverage. This may require changing and/or adjusting heads and nozzles. Making these changes can save you money. Sometimes we don’t know there are coverage issues until we see failing plants at which point it means replacing costly plant material.
• With newer technologies and advanced irrigation product design available, you may want to consider changing out older irrigation components for newer products. The irrigation industry has made many advances, especially in the area of water conservation.

Remember that irrigation is a watering supplement. Don’t overwater your plants. Give them time to become thirsty; this will help build a healthy root system because the roots will grow deep looking for water.

These are just a few suggestions that you can undertake to do your part to help conserve water resources and – at the same time – save yourself some money.

-Sean Jones, Irrigation Engineer

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

Volunteers Help Make Smithsonian Gardens Shine

We think our Smithsonian Gardens volunteers are awesome! From helping out in the Archives of American Gardens and greenhouses to volunteering as interpreters in our exhibits and gardens, volunteers help sustain some of our most important projects and serve as terrific ambassadors to our visitors.

 This winter, over forty volunteers signed up to share their enthusiasm for orchids with visitors to our Orchids of Latin America exhibit. Their knowledge, love for all things orchid, and great people skills mean that those who come to see the exhibit have the opportunity to ask questions and learn more about the beautiful plants on display. If you have yet to visit the exhibit, make some time to stop by the National Museum of Natural History’s special exhibition gallery to see the beautiful display and say “hi” to the volunteers working there.

Orchid Family Day 2013. Francisco Guerra, photographer.

Although the orchid exhibit ends April 21st, many of our volunteer interpreters are staying on with Smithsonian Gardens to interact with the public in the gardens this spring through fall. If you are interested in meeting great people and sharing your love of plants with visitorsfrom around the world, think about joining us out in the gardens. We are always excited to welcome new volunteers and interpreters to our team! For more information or to volunteer, visit the web or send us an email.

-Alison Kootstra, Education & Outreach Intern

Rustic Ornament in the Victorian Garden

This Stump Pedestal is an example of a popular Rustic Style of garden ornament that developed in the late nineteenth century. This style was adapted to the garden from the Romantic Movement, which was characterized by its nostalgic look at nature. Its love of picturesque landscapes was recreated in the garden. The “English Landscape Garden” or “Jardin Anglaise” relied on objects in the rustic style to create an informal setting that put an emphasis on the true nature of the land.

1979.26, Pedestal, Rustic Stump, late 19th C, Cast-iron, paint, 22 x 18 x 13.

These gardens were more sparsely ornamented than other garden styles. Objects were often created using materials found in nature such as tree branches, twigs, roots, bark, pinecones, animal horns, antlers and seashells and were often handmade. Cast-iron, already a popular material used in the garden used molds that would mimic these natural assemblages. As we see in the rustic stump pedestal, it is cast in a high relief and mimics the look of a tree trunk with thick bark that is entangled roots and oak leaves. It would have been used as a base for a plant stand or bird bath and occasionally could have been used a planter itself. These objects were usually painted in white, black, or natural colors that would blend in with the landscape.

Horticulture magazines and other serials provided layout, planting, ornament and structure designs that would have incorporated objects such as the stump pedestal. This was a popular item that can be seen in the 1858, Janes, Beebe, & Co. New York trade catalogue, the 1875, Coalbrookdale Company of England trade catalogue, and the 1893, J.W. Fiske Iron Works trade catalogue.

Many of these rustic style cast-iron ornaments have been broken or damaged. However, gardeners still feature them in their landscapes today.  Using the broken pieces and fragments of these antique garden furnishings, they create interesting displays that incorporate the past and create a nostalgic and picturesque setting for the present.

Further Reading:
Israel, Barbara. Antique Garden Ornament: Two Centuries of American Taste. New York: Harry N. Abrams, Inc., 1999.
Himmelheber, Georg. Cast-iron Furniture, and all other forms of iron furniture. London: Philip Wilson Publishers Ltd, 1996
Hill, May Brawley. Furnishing the Old-Fashioned Garden: Three Centuries of American Summerhouses, Dovecots, Pergolas, Privies, Fences & Birdhouses. New York: Harry N. Abrams, Inc., 1998.

 -Janie R. Askew
Research Assistant, Smithsonian Gardens
MA Candidate, History of Decorative Arts
The Smithsonian Associates/George Mason University

I Yam Not a Tortoise but a Plant

The caudex of the Dioscorea mexicana.

Dioscorea mexicana, commonly called Mexican Yam or Tortoise Plant, is native to Mexico, El Salvador, and Panama.  Dioscorea is made up of around 600 species in the Dioscoreaceae family and has a world-wide distribution range.  Originally in the Testudinaria genus and named after ‘Testudo,’ a genus of tortoise, it was later grouped into the genus Dioscorea.

The plant’s caudex (or modified stem) resembles the shell of a tortoise.  The caudex itself is a partially exposed tuber that is covered in grayish-brown scales.  It is divided into polygonal plates that are scored by deep furrows.  This species typically goes dormant during the winter, though this year even without water for nearly four months the stem didn’t die back and still looks great, so we shall see what the future holds.  From what I have experienced, heard from other growers, and also read, this plant sometimes either doesn’t die back during the winter or sends out a new stem earlier or later than expected, so watch the plant and not necessarily the calendar.  The new stem can grow 15 to 20 feet in one season!

Dioscorea mexicana’s flowers bloom in late summer.

Dioscorea mexicana is dioecious meaning that the individual plants in the species are either male or female.   The leaves are glossy green and heart-shaped.  Flowers are greenish with dark purple centers and bloom in late summer.  Although considered inconspicuous, I feel the male flowers add some visual interest.  The caudex requires shade, usually provided by surrounding vegetation, while the vining portion of the plant needs full sun.  It prefers to grow in a well-drained soil.  Dioscorea mexicana is mostly propagated by seed, but although stubborn can be grown from cuttings.

If you can find one, this plant will have even the best plant enthusiasts talking and asking questions.  Its easy winter care regimen (in most years) makes it a great choice for an exotic tropical look.  During winter months greatly reduce the amount of water given to the plant; a light monthly watering is needed at most.  I couldn’t find much information about and personally don’t know its hardiness but wouldn’t expose it to temps much below freezing for extended periods of time.  Slowly bring it out of dormancy in the spring and give it lots of water during the hot growing summer season.   Despite being nicknamed after a slow mover, Dioscorea mexicana quickly proves itself a crowd pleaser!

-Matt Fleming, Horticulturist

Smithsonian Gardens presenta Las Orquídeas de Latinoamérica

Oncidium Red Stars ‘Rooster’

La Institución de Smithsonian tiene una larga historia de la recolección de plantas para compartir su belleza con el mundo. ‘Smithsonian Gardens’  sigue compartiendo esta tradición a través de su colección de orquídeas. Esta colección ha aumentado desde 1974 cuando adquirieron las primeras cinco plantas. Desde entonces, la colección de orquídeas ha florecido enormemente y hoy  tenemos a más de 8,000 especies en nuestro invernadero.

Las plantas que forman esta colección son utilizadas para elevar la belleza y la maravilla de los museos Smithsonian. Cada año podemos disfrutar la gran variedad de sus brillantes colores y formas cuando muestran sus encantadoras flores. Aprovechen y celebren estas maravillosas plantas cuando visiten a los museos Smithsonian. Podrán ver orquídeas que representan a países tan lejanos como China o más cercanos como nuestros vecinos de México.  La exposición este año celebran Las Orquídeas de Latinoamérica. Visiten y admiren las bellas flores exóticas que tenemos en exhibición en el Museo Nacional de Historia Natural y reciban más información y detalles que les ofrecemos en español e inglés.

- Sarah Mirabal, Orchid Intern

Victorian Love of Nature, Ornament and Decoration on Display

OH.1985.32, Plant Stand, c. 1850-1900, Cast-iron, 44” x 25.5”

Plant stands such as this, from the Smithsonian Gardens’ Garden Furnishings and Horticultural Artifacts Collection, were the perfect tool to combine a love of nature with a taste for ornament and decoration in the Victorian Era. Named for Queen Victoria of Great Britain, the Victorian Era classifies the period of society and the fine and applied arts during her reign from 1837 to 1901.The cultivation of plants was a widely popular pastime for the Victorians in all levels of society, and their toils were proudly displayed in homes and gardens. Plant stands became an essential item for the exhibit and storage of flowers and foliage. Their practical and decorative benefits were amplified by the link they provided between the domestic interior and the natural world that had gone missing due to the Industrial Revolution.

Plant stands were manufactured in England, America, and France, and came in a variety of forms and materials. Cast- and wrought-iron were the most common materials for garden ornaments such as this; however, they also came in wood, wicker, glass, and ceramic versions and were usually painted white, black, brown, or green.  Circular, semi-circular, or squared structures could be positioned against a wall or in the center of a space. Single level and tiered versions were popular, in addition to the plant stand we see here that has multiple appendages.

This type of plant stand was made using separately cast arms attached to a central axis rod. The arms could be rotated and moved vertically along the pole to display plant specimens of various sizes. The cup at the end of each arm would hold a small flower or foliate, which were often in their own removable liner so they could be changed out seasonally.

 Plant stands are still a popular indoor and outdoor garden accessory for displaying plants. Just as they did during the Victorian Era, they showcase a selection of seasonal varieties to beautify the home and bring nature within reach.

 Further Reading:
Israel, Barbara. Antique Garden Ornament: Two Centuries of American Taste. New York: Harry N. Abrams, Inc., 1999.

 -Janie R Askew
Research Assistant, Smithsonian Gardens
MA Candidate, History of Decorative Arts
The Smithsonian Associates/George Mason University