Description: This native perennial vine is up to 15'
long and non-woody. The stems twine about adjacent vegetation and fences,
climbing upward toward the light. These stems are light green, round in
circumference, and shiny; they often have lines of
fine white hairs. Opposite leaves up to 6" long and 2½" across occur at
intervals along the stems. They are triangular-cordate, glabrous, and dark
green. Their margins are smooth, but sometimes undulate up and down. The sinus
of the leaf blade is somewhat flattened. The petioles are up to 3" long and
often reddish green. A milky sap is absent from the foliage. From the axils of
the middle to upper leaves, there are small clusters of flowers. Each flower is
white or pinkish white and up to ¼" long. The structure of each flower
consists of a light green calyx with 5 lanceolate lobes, a white corolla with 5
linear lobes (sometimes with pink tips), and a white corona (or crown-like
appendage) surrounding the reproductive organs in the center. The lobes of the
corolla are semi-erect and rather twisted. The corona is divided into 5
segments; each segment has 2 linear extensions at its apex that are rather
membranous and twisted. The blooming period occurs from mid-summer to early
fall and lasts about 1-2 months. The flowers have a strong honey-like
fragrance. If cross-pollination of a flower occurs, there develops a smooth
follicle up to 4" long that tapers gradually to a point at one end. This
follicle is initially green, although it laters becomes reddish green and
finally brown. When the follicle splits open along one side, it releases
numerous seeds. Each seed has a large tuft of white hairs, which enables
distribution by the wind. The root system consists of a taproot and long
rhizomes. This vine reproduces by vegetative offsets or by reseeding
itself.
Cultivation: The preference
is full or partial sun, and mesic to dry conditions. Almost any kind of soil is
tolerated, including those that contain loam, clay, gravel, or sand. Bluevine
can be difficult to get rid off because new shoots can develop from the root
system after the entire vine has been pulled. The seeds don't germinate until
late spring or early summer.
Range &
Habitat: Bluevine is occasional to locally common in southern and
central Illinois, while in the northern Illinois it is uncommon or absent (see
Distribution
Map). Habitats include thickets, banks of rivers
and drainage
ditches, gravelly areas along railroads and roadsides, cropland, overgrown
vacant lots, shrubbery in yards, and fence rows. Bluevine adapts quite well to
disturbed habitats and is rather weedy.
Faunal
Associations: The nectar of the flowers attracts Halictid bees,
Masked bees (Hylaeus spp.), wasps, flies, and Monarch butterflies. Among the
flies, are such visitors as Bee flies, Thick-headed flies, Tachinid flies, and
Bottle flies. The caterpillars of the butterfly Danaus plexippes
(Monarch) feed on the foliage, while Aphis nerii (Milkweed Aphid) sucks
juices from the foliage. Mammalian herbivores avoid consumption of the foliage
because of its bitter taste and poisonous properties.
Photographic Location: The upper photograph was
taken near a railroad in Champaign, Illinois, while the lower photograph was
taken at fence row near the webmaster's apartment complex in Urbana,
Illinois.
Comments: Bluevine is
often referred to as Cynanchum laeve; its scientific name has changed
occasionally through the years. Other common names for this species are
Honeyvine and Sandvine. A few members of the Milkweed family in Illinois are
twining vines, rather than erect herbaceous plants. Most of these occur in
southern Illinois in swampy habitats; they are currently classified as
Matelea spp. (Climbing Milkweeds), although they were assigned to the
Gonolobus genus in the past. The flowers of the Climbing Milkweeds have
larger flowers with spreading corolla lobes; they are variously colored. The
flowers of Bluevine are smaller with more erect corolla lobes. An introduced
species, Vincetoxicum nigrum (Black Swallow-Wort), occurs occasionally
in Illinois. It was formerly known as Cynanchum nigrum. Black
Swallow-Wort has leaves that are rounded at the base and its flowers are
brownish purple. All of these vines produce follicles (seedpods) that resemble
those of other members in the Milkweed family.