Daily Invader

Chesapeake Bay Plants

Asian Sweet Flag (Acorus calamus)


Asian Sweet Flag (Acorus calamus) an expectorant and an anesthetic.

Asian Sweet Flag is a medicinal plant from Asia used for centuries as an expectorant and an anesthetic. It was brought to Europe in 16th century. It is a strange plant in that it doesn’t sexually reproduce as it's sterile with infertile flowers, but it does reproduce asexually by splitting its rhizomes (underground stems). In North America there is a similar species, also called Sweet Flag (Acorus americanus), that does sexually reproduce and is often confused with the sterile Asian plant. Because Asian Sweet Flag was such an important medicinal plant in Europe, it was introduced to North America very early; the first herbarium collection is from Philadelphia in 1824. It was found in Chesapeake Bay in the mid to late 1800s, and was likely both an intentional introduction as a garden plant and an unintentional one with dry ballast (rocks and dirt used for weight on sailing ships). In spite of its history as an important medicinal plant, it is no longer seen as economically valuable in our region. Complete Record 




Redtop (Agrostis gigantean)


Redtop (Agrostis gigantean) is in yards and pastures across the US.

Redtop is a common grass used in both lawns and pastures; it is a perennial grass that makes good coarse, dense turf. Redtop gets its name for its reddish flowers and has been planted across the US, Canada, Europe and its native Eurasia. Beyond the lawns and pastures in which it is planted, it grows in areas with moist soils such as meadows, and fresh and brackish tidal marshes. It is widespread throughout the Chesapeake Bay watershed where it was reported as far back as 1837. In the mid 1800s, it likely arrived with dry ballast (rocks and soil used to weight sailing vessels) but it was also widely spread through intentional planting and agriculture. The US Department of Agriculture calls it one of the most widely adapted grasses and it is used in restoration projects for erosion control, stabilizing river and ditch banks and other critical areas, and covering strip mine soils because it is adapted for moist soils and germinates rapidly. Complete Record


Tree-of-Heaven (Ailanthus altissima)


Tree-of-Heaven (Ailanthus altissima) reaches to the sky.



The Tree-of-Heaven is native to northern China where it has a rich history dating back hundreds of years. It is fast growing and can reach 80 feet in its relatively short life (<50 years). It is used as an astringent in traditional Chinese medicine, but can be toxic to domestic animals and cause allergic reactions for some people. It was brought to North America in 1820 as an ornamental tree and, in spite of its foul-smelling flowers, was planted in many urban areas because of its rapid growth and tolerance of urban stresses. It didn’t take long before it started to spread into disturbed sites and adjacent woodlands. It is currently found in 43 states including the Chesapeake Bay watershed, where it was planted in 1876 in Washington DC area. Today it is widespread in the Chesapeake Bay watershed, but there is only one report from tidal wetlands - thus it is listed as a boundary resident in the database. Complete Record 


Alligatorweed (Alternanthera philoxeroides)


Alligatorweed (Alternanthera philoxeroides) transported to Virginia with a load of asparagus. 


Alligatorweed was likely transported to Mobile, AL on ships’ dry ballast (rocks and dirt used to weight a sailing vessel) in 1897 from South America (Brazil-Argentina) where it is native. It spread though much of the Southeast in the following years, reaching Hampton VA in 1953 on a load of asparagus from the Carolinas. The winters in much of the Chesapeake Bay region are too cold for this species so it is restricted to watersheds in the lowermost Bay. In the southeast, where it is more abundant, it was the target of a successful biological control program. As a result, it is largely controlled by several South American insect species brought in by the United States Department of Agriculture from 1964-71. Complete Record


European Marsh Mallow (Althaea officinalis)


European Marsh Mallow (Althaea officinalis) a medicine and the original marshmallow candy.


European Marsh Mallow, as the name suggests, is a marsh plant native to Eurasia. The root of this beautiful pink flower was the original source of marshmallows and gave the favorite campfire treat its name. For more than 2000 years the plant was used for various medicinal purposes, including remedies for the common cold, sore throat, cough, inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, indigestion, and stomach ulcers. It is still used as a medicinal plant today; the dried leaves and roots are used in teas and alcoholic extracts (tinctures) and the roots are used in ointments and creams, cough syrups, or powdered in capsules. Due to its popularity and importance as a medicinal and ornamental plant during colonial times, it was very likely imported to North America in this period. The first record of its occurrence in the Chesapeake Bay region is from 1875. It has since been found in several locations in Maryland and Virginia but remains relatively rare. Complete Record 


False Indigo (Amorpha fruticosa)

False Indigo (Amorpha fruticosa) a popular garden plant and now a garden escapee.

False Indigo has beautiful purple flowers and is a popular garden plant. It is native to Florida and Louisiana north to North Carolina, and from the Midwest east to western Pennsylvania, but has been introduced to New England and the Pacific Northwest. The first report of its wild occurrence in the Chesapeake area was in Potomac Park, Washington DC, in 1898. It is considered an occasional garden escapee in the Chesapeake Bay Region because it was absent in nineteenth-century floras from the Washington-Baltimore area, and all early reports were in areas where it was known to have been planted. It is now an abundant plant in fresh and brackish tidal marshes around the Bay, and may be competing with native wetland shrubs on the northeast coast and the Columbia River in the Northwest. It is now listed as an invasive plant in several states. Complete Record  



Asparagus (Asparagus officinalis)


Asparagus (Asparagus officinalis), like many common food crops, was imported from Europe.  

Every spring many of us harvest the new shoots of Asparagus out of our gardens or look for the patches of wild Asparagus in our neighborhood parks. Asparagus was brought to North America from France back in the 1600 and 1700s but didn’t become a commercially grown crop until the 1860s. Asparagus is originally from the Europe, North Africa, and Asia, where it grows wild along the seashores and riverbanks. It was probably domesticated by the Romans and has been widely cultivated ever since. Wild Asparagus, or rather garden escapes, were seen as early as the 19th century. In North America Asparagus grows all along the east coast and in scattered locations across temperate North America and worldwide. In the US it has grows in 36 states. Asparagus was reported in the Chesapeake as far back as the 1800s and is common on sandspits, beaches, and marsh edges, but is primarily an upland garden plant. Complete Record 



Orach (Atriplex patula)


Orach (Atriplex patula) is a shoreline plant that was spread from its initial introduction point by currents and other natural dispersal mechanisms.  

Orach (also called saltbush) is a shoreline plant that lives in salty soils at the margins of salt marches and beaches. It is widely distributed in the Northern Hemisphere and has been introduced to many areas of the world. This wide distribution has resulted in some disagreement about whether it is native or introduced in North America. We consider it introduced based on its occurrence on dry ballast (rocks, etc. used to weight old sailing vessels in the 1600-1800s) and because it is mostly found in disturbed habitats. Orach likely arrived in dry ballast from Europe sometime before 1848, probably much earlier (1600s) because it was well established by the late 1800s. The earliest records in the Chesapeake region were from in Hampton Beach VA in 1872 and Washington DC in 1877. Orach is rare in the Chesapeake and so no impacts have been reported. Complete Record  


Halberd-Leaved Orach (Atriplex prostrata)


Halberd-Leaved Orach (Atriplex prostrata) loves salty soils.  


Halberd-Leaved Orach is native to Eurasia and was introduced to North America by dry ballast piles (rocks, etc. used to weight old sailing vessels in the 1600-1800s) sometime before the 1800s. Halberd-Leaved Orach is extremely tolerant of salt and can retain salt in its leaves. They grow is salty soils along the shore and in salt marshes. Halberd-Leaved Orach is similar the Orach species (Atriplex patula), but much more common. Early on the taxonomy of both species was confused leading to inconsistencies in their life histories in North America. The first record of Halberd-Leaved Orach in Chesapeake Bay was in 1806 from Virginia and in 1877 in Washington DC. It is now common in brackish marshes, and shorelines of Bay. Complete Record 


Yellow Rocket (Barbarea vulgaris)


Yellow Rocket (Barbarea vulgaris) introduced from Europe in the early 1800’s. 

Yellow Rocket is a lovely looking ‘wildflower’ common in many fields and roadsides. It was spotted in Baltimore around 1837 and soon after in Washington DC and beyond. Yellow Rocket is not usually considered to be an aquatic plant but it has been reported from the upper parts of Brent Marsh on the Potomac and along beach margins in Kent County, MD, which is why it is listed in the database as a boundary resident. It is an agricultural weed that was likely brought over from Europe on a wooden sailing ship. One could imagine the seeds being mixed in with the hay used to feed the livestock brought across the Atlantic. Agriculturally, it has had significant impacts and is listed as a noxious weed in 35 states. Complete Record  




Hairy Sea-Blite (Bassia hirsuta)


Hairy Sea-Blite (Bassia hirsuta) is a great example of a species spreading naturally into new areas from a central introduction location.

Hairy Sea-Blite is a shoreline plant growing in dunes, along the beach, and in sandy areas of marshes. It is native to Europe from southern Scandinavia to the northern Mediterranean coast. It was discovered in North America in the early 1900s, first in Boston, MA (1908) then in Long Island, NY (1915). These first introductions were likely a result of dry ballast (rocks and dirt used for weight on sailing ships). From these introductions it spreads north and south along the coast and is now present from New Hampshire to Virginia. Much of this range expansion was likely due to natural dispersal from the original point of introduction. Hairy Sea-Blite arrived on Chincoteague Island (1983), Ocean City (1941) and Assateague Island (1967) probably through natural dispersal. It probably has found its way to the Eastern Shore of lower Chesapeake Bay, but there are no specific records. Complete Record 




Ozark Tickseed-Sunflower (Bidens aristosa)


Ozark Tickseed-Sunflower (Bidens aristosa) sticks to your socks and can come home with you.




Ozark Tickseed-Sunflower is native to the Midwestern United States but has spread too much of the East Coast from Maine to Florida. This plant is an agricultural weed and was likely spread by the import of food crops or wool from western sheep pastures. The seeds are barbed and are easily transported in animal’s coats and in people’s socks and clothing. It was first discovered in along the Potomac River near Glen Echo MD in 1902 and from other Potomac sites from Key Bridge south to King George County. It is very common in wet areas along river banks and in marshes but is also found in fields and along the roadways. It has been found in the upper edges of tidal marshes but is much more abundant in adjacent upland habitats and roadside ditches. Ozark Tickseed-Sunflower is listed as an invasive plant in Maryland, Delaware, and Kentucky because can crowd out native plants in wetlands but generally is not seen as an economically important weed. Complete Record 


Carolina Fanwort (Cabomba caroliniana)


Carolina Fanwort (Cabomba caroliniana) is a southern plant brought north by the water garden and aquarium trade.


Carolina Fanwort is an aquatic plant native to streams and ponds in the southeastern United States. Fanwort was originally thought to range from Virginia or New Jersey south to Florida and West to Ohio and Texas. Its distribution is spotty North of North Carolina and its northern spread into Maryland and Washington DC has likely been helped along by the water garden and aquarium trade. Carolina Fanwort is a very common water garden and aquarium plant than has been sold and subsequently released into waterways as far north as New England as well as in the Pacific Northwest, Washington and Oregon. Most of the early records of this species North of Virginia from fish ponds or other ponds where the plant was intentionally planted. There are some records from the Patapsco River, Dyke Marsh, Alexandria VA, and the tidal Potomac but it remains rare. Complete Record 


Eurasian Sea Rocket (Cakile maritima)


Eurasian Sea Rocket (Cakile maritima) came over with the first European settlers. 

Eurasian Sea Rocket is native from northernmost Scandinavia to the Mediterranean and Canary Islands. It arrived to the United States in dry ballast in the 1800s. The first definite record was from dry ballast piles in Philadelphia in 1876. It is now found sporadically along the Coasts from Maine to Texas and on the Pacific Coast. The first report in Chesapeake Bay on ship's dry ballast in Newport News, VA in 1921. By the 1950s it was found as far North as Baltimore Harbor, nearly all early occurrences are near seaport but some specimens have been collected on beaches in Anne Arundel and Queen Anne's County, Maryland. Complete Record 





Hedge Bindweed (Calystegia sepium spp. sepium)


Hedge Bindweed (Calystegia sepium spp. sepium) is a nonnative variety of a common native plant. 


Hedge Bindweed is a vine that grows in the upper zones of fresh to brackish (polyhaline) marshes and fields in all regions of the Chesapeake Bay. Hedge Bindweed is the common name given to all Calystegia sepium plants in the area, but in this case there are several subspecies and some are native and one, Calystegia sepium spp. sepium, is introduced from Europe. These subspecies are often not distinguished in collections, making the history and distribution of the introduced variety difficult to trace. The native subspecies are widespread throughout North America, but the introduced plant is confined to the East Coast. Based on careful analysis of various herbarium collections, researchers have found evidence for an early introduction starting from the 1800s. In the Chesapeake Bay region the European variety is thought to be common but the plants are not generally identified beyond the species level making it difficult to distinguish between the native and introduced varieties. Plants with white flowers are probably the introduced subspecies, while those with pink and white flowers are probably native, but hybrids may occur. Complete Record 


False Daisies (Eclipta prostrate)


False Daisies (Eclipta prostrate) are on nearly every continent.




False Daisies have small round white flowers and grow in wet disturbed areas. They are widespread in the tropics and are sometimes a crop weed. With such a wide distribution it’s difficult to know their origin or means of possible means of introduction. Because some reports consider them native to North America and others that say they are native to Asia, we consider them cryptogenic (status unknown). False Daisies were present in the Southeastern US from Virginia to Florida in the 1700s and from western Pennsylvania and Ohio southward starting in the late 1800s. In all, False Daisies have been found on all continents except Antarctica and are considered a weed in 35 countries. If they are introduced to North America, dry ballast (rocks, etc. used to weight sailing vessels in the 1600 and 1700s) seems to be a likely vector. False Daisies are included here because they occur in the upper edge of fresh-brackish tidal wetland environments in Chesapeake Bay. Complete Record


Yellow Iris (Iris pseudacorus)


Yellow Irises (Iris pseudacorus) were in the gardens of our forefathers.


Yellow Irises are beautiful plants that grow in both freshwater and saltwater wetlands. They are native to central Scandinavia south to Turkey and North Africa. Because they are so attractive, they were likely imported as a garden plant. Thomas Jefferson grew this iris at Monticello in Charlottesville, VA before 1771. But like many garden plants, they can grow in natural wetlands and marshes, and in the 1860s they were reported on the Delaware River, in the Hudson River Valley, and in the Chesapeake Bay region (Washington and Baltimore) by the early 1900s. These days they grow in wetlands and marshes in 40 states, and are only absent, for now, in some plains and mountain states. Even though they are so widespread few negative impacts have been reported, which is surprising given that these plants are toxic to some grazers like livestock. But in most locations, they are not abundant and are frequently trampled and killed by high densities of livestock. Their toxicity may be more problematic for native grazers because they can replace edible native plants. Complete Record 


Eurasian Watermilfoil (Myriophyllum spicatum)


Eurasian Watermilfoil (Myriophyllum spicatum) is an imported ornamental that is now an invasive weed.




Eurasian Watermilfoil is native to Eurasia, and was probably imported as an ornamental plant by government workers in the 1940s and through the ornamental plant trade around the same time. The first confirmed record is from Belch Springs Pond, in Washington DC in 1942, however, there were reports from Maryland in the 1930s, but due to possible confusion with the native American Watermilfoil (Myriophyllum sibericum), the identity of those plants was never verified. After its introduction to the Chesapeake Bay region in the 1940s, Eurasian Watermilfoil spread rapidly; attaining extremely high abundances and biomasses through the 1950s and early 1960s, and it was during this time that its economic impact was the greatest. At the same time, the plant also spread swiftly across the US through the ornamental plant trade, aquarium and fishpond escapes, and by trailered boats and possibly by birds. By 1987, it was present in 34 states and 3 provinces. Today Eurasian Watermilfoil considered an invasive weed throughout its introduced range. Complete Record


Mile-a-Minute (Polygonum perfoliatum)


Mile-a-Minute (Polygonum perfoliatum) is a rapidly growing weed that overgrows other plants.

Mile-a-Minute weed is native to eastern Asia including the Philippines, India, Korea, China, and Japan. In the 1930s a nursery in York County Pennsylvania started selling it as an ornamental plant. But as it got more popular and started to spread into wild areas, people started to see it is a troublesome weed. Seeds and plants from established populations in Pennsylvania were spread to Maryland and Virginia by birds and water dispersal through the Susquehanna, Deer Creek and Gunpowder River drainages. Mile-a-Minute is found in both terrestrial habitats and wetlands. While most of the records are from nontidal habitats, it has invaded the beaches and marshes in the estuaries of the upper Chesapeake Bay. Mile-a-Minute is a serious concern in the Chesapeake Bay watershed because of its extraordinarily fast growth, up to 2 cm/day, and because it covers other vegetation including more desirable wildlife food plants and Kudzu. Although it is edible for grazers, Although it is edible for grazers, its prickly foliage is hard to walk through, let alone eat. Complete Record



Multiflora Rose (Rosa multiflora)


Multiflora Rose (Rosa multiflora), planting it seemed like a good idea at the time.

“The world is a rose, smell it and pass it to your friends” so goes a Persian proverb. The fragrant Multiflora Rose, like most roses, is native to Asia, and like the proverb suggests, this rose has been passed around. It was introduced to the United States as an ornamental plant in the 1800s, and in the mid-20th century it was promoted by the United States Department of Agriculture Soil Conservation Service to prevent soil erosion. At that time, it was considered a great plant to introduce because it not only prevented soil erosion, but was beautiful and thought to be good for wildlife. It was initially planted in the Chesapeake Bay watershed for erosion protection and as an attractive living fence. Unfortunately, like many other introductions that seemed great at the time, it soon became a serious pest throughout the US, including the Chesapeake watershed where it is now regarded as a serious invader. It is an upland plant, but occasionally occurs at the edge of tidal wetlands. Complete Record


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