bittersweet nightshade (Solanum dulcamara)
SCIENTIFIC SYNONYMS: There are no scientific synonyms for
Solanum dulcamara L.
CONFIRMATION STATUS: Pending confirmation.
TAXONOMY: The currently accepted scientific name of bittersweet
nightshade is Solanum dulcamara L. Two varieties are recognized in
North America: 1) Solanum dulcamara L. var. dulcamara, and 2)
Solanum dulcamara L. var. villosissimum Devs. Only variety dulca-
mara is reported occurring in Virginia.
NATIVE STATUS: Introduced, United States and Canada.
Probable causes introduction to North America are cultivation by early
settlers and agricultural and shipping activities in the Pacific Northwest.
The earliest reports of bittersweet nightshade's establishment outside of
cultivation in North America are from the Great Lakes region, where it
occurred by the mid-1800s.
GENERAL BOTANICAL CHARACTERISTICS: This adventive
perennial plant is listed by various authorities as a forb, vine, subshrub,
or shrub (for this description, we will treat it as a vine). As a semi-woody,
rhizomatous vine the aboveground stems are typically about 10 feet long,
sometimes growing as long as 23 feet. Its base is woody, and the above-
ground branches are herbaceous and die back each year. It can become
semi-erect by climbing over adjacent vegetation or fence rows, otherwise
it sprawls along the ground, and, to a limited degree, grow erect. The stems
are initially purple and slightly pubescent, or they have scattered appressed
hairs. Later, they become brown and woody. These woody stems are semi-
hardy and may survive some winters to produce foliage. The alternate
leaves are up to almost 5" long and 2½" across. The larger leaves have a
triangular outline and 3 deep lobes. These lobes are broadly ovate or
cordate, with the terminal lobe being much larger than the side lobes. The
margin of each leaf is smooth, while the upper surface is either glabrous or
has scattered appressed hairs. The terminal lobe tapers gradually into an
elongated tip. The smaller leaves often lack lobes and have an ovate shape,
otherwise they are quite similar to the larger leaves. The foliage exudes a
rank bitter odor, particularly when the leaves or stems are damaged. Occa-
sionally, angular clusters of 6-12 violet flowers (sometimes as many as 30)
are produced from the stems or the axils of the leaves. The flower buds and
their branching stalks are also violet. Each flower is about 1/3" across, con-
sisting of a purple corolla with 5 triangular lobes, several yellow anthers
that are united together to form a slender cone, and an inconspicuous style
that extends beyond the anthers. As the lobes of the corolla unfold, they
spread outward and then curve sharply backward to expose the anthers. The
small calyx is green, purple, or brown, and has 5 shallow lobes that are well-
rounded. It is persistent and slightly pubescent. There is no noticeable floral
scent. Each flower is replaced by a shiny little fruit that is oval in shape and
about ¼" long. Each fruit is initially green, but later turns yellow or orange,
and finally becomes bright red. The fruit is juicy and contains yellow seeds
that are circular in shape and flat-sided. The root system produces abun-
dant rhizomes that become somewhat woody with age. Bittersweet night-
shade spreads by rhizomes. The main root grows horizontally just below
the soil surface, sprouts frequently, and can branch 3 to 5 times. Roots of
bittersweet nightshade have secondary growth and an epidermis that is
protected by a layer of suberin at the root cap. This plant often forms
sprawling vegetative colonies.
REGENERATION PROCESS: Bittersweet nightshade reproduces by
seed and locally through vegetative regeneration (rhizome spread). In
North America, bittersweet nightshade berries are produced throughout
summer and fall and may remain on the plant until winter. Bittersweet
nightshade seeds are dispersed primarily by birds. Birds consume the
fleshy fruit, digest the pulp, and spread undamaged seeds by regurgita-
tion or defecation . In eastern states and the Great Lakes region, most
bittersweet nightshade fruits were eaten and seeds dispersed shortly
after fruits ripened in July and August. Birds continued to forage on
bittersweet nightshade fruit into the fall but to a lesser extent than in
summer. Mammals also eat bittersweet nightshade fruit and disperse
its seed. In eastern North America, white-tailed deer eat the fruit of
bittersweet nightshade and have the potential to aid in the long distance
distribution of its seed.
HABITAT TYPES: Habitats include openings in woodlands, moist
thickets, mesic deciduous woodsbrushy areas and rock piles, fence rows,
gardens and edges of yards, and miscellaneous waste areas and clearings.
This plant prefers disturbed areas, although it sometimes occurs in natural
habitats. In eastern and Great Lakes states, sparse amounts of bittersweet
nightshade occasionally occur in open habitats such as remnant prairie and
grasslands, moist savanna, and mesic tussock meadow. Bittersweet night-
shade commonly occurs in habitats associated with water, such as riparian
areas, swamps, marshes and bogs, wetlands, lake shores, forested fresh-
water dune barriers, pond edges, canal banks, floodplains, ditches, and
SITE CHARACTERISTICS: Bittersweet prefers full or partial sun, and
moist to mesic soil that is loamy and fertile. Bittersweet nightshade, how-
ever, occurs in a variety of soil types and textures, including shallow soils
consisting mostly of humus, sand, gravelly loam, and rich loam and clay.
Bittersweet nightshade appears to be most abundant in riparian habitats.
Nonetheless, because of its robust nature, this plant can adapt to drier con-
ditions and other kinds of soil. It can spread aggressively and be difficult to
get rid of because small pieces of rhizome in the soil can regenerate new
SEASONAL DEVELOPMENT: The blooming period usually occurs
during the summer and lasts 2-3 months.
GENERAL DISTRIBUTION: Bittersweet nightshade has an unusual
distribution. It is found from Florida north to Maine (except South Carolina)
and into the Canadian maritime provinces. It is however, absent from the
Gulf of Mexico bordering states Arkansas and Arizona. It is also found in
all the southern Canadian provinces (except Manitoba and Alberta); it is
not found in the northern Canadian provinces.
SKY MEADOWS DISTRIBUTION:
Vine specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
The specific distribution of bittersweet nightshade has not been determined.
IMPORTANCE AND USES: Primary pollinators of bittersweet night-
shade are bumblebees; occasional pollinators include solitary bees, sweat
bees, and syrphids flies. In general, bittersweet nightshade is not a major
food source for any invertebrate species other than bumblebees. Birds
typically digest the fleshy portion of bittersweet nightshade's fruit and
expel the seed. Birds adapted to foraging in vegetation, which can reach
fruit while perched on a branch and are not restrained by a small gape, are
more likely to eat bittersweet nightshade fruit than birds lacking these
characteristics. Frugivorous birds such as crows, eastern kingbirds, mimic-
thrushes, thrushes, white-crowned sparrow, and waxwings eat the fruits of
bittersweet nightshade. Numerous other songbirds and upland gamebirds
throughout the United States also eat bittersweet nightshade fruit, especial-
ly in the Northeast and Southwest. Ring-necked pheasants eat the fruit of
bittersweet nightshade, especially as an emergency food source during ice
storms. In the United Kingdom, bittersweet nightshade fruit is the primary
food for blackcaps, and is also used by blackbirds, song thrush, robin,
starling, and spotted flycatcher. Bullfinches are the only known bird that
regularly eats bittersweet nightshade fruit for its seed rather than its flesh.
Mammals that occasionally eat bittersweet nightshade fruit include black
bear in Oregon , Virginia opossum in New York, eastern cottontail rabbits
in Massachusetts, white-tailed deer in the eastern United States, as well as
raccoon, striped skunk, and pocket gopher. Common muskrats also graze
on the stems of bittersweet nightshade.
While not preferred, bittersweet nightshade is occasionally used for nesting;
however, nesting success (i.e., percent hatched) was lower in nests con-
structed in bittersweet nightshade than in nests constructed in most native
Bittersweet nightshade has been studied primarily for its secondary
chemicals and used for its medicinal properties. Bittersweet nightshade
contains small amounts of compounds that have been studied for their
potential medicinal importance. In North America bittersweet nightshade
was widely prescribed for its narcotic, diuretic, alterative, and cleansing
principles during the latter half of the nineteenth century. It was thought
to relieve many ailments including leprosy, skin diseases, cutaneous
diseases, rheumatic infections, ulcers, sores, and gland swelling. Although
bittersweet nightshade is not widely used today, extracts from its roots,
bark, and shoots are still prescribed for their narcotic principles in rheu-
matism, circulation, ulcers, and skin afflictions.
Crooked Run Valley