Woolly pipe-vine is a twining, high-climbing woody vine characteristic along streams in the Ozarks. Hikers and canoeists often don’t notice it because the leaves and unusual flowers are usually high overhead in the trees.
Leaves are alternate, simple, the blades 3–6 inches long, 2–3½ inches wide, heart-shaped, the tip blunt to rounded, the base heart-shaped, the margin entire; the upper surface is dark green, somewhat densely hairy with matted wool; the lower surface is pale, densely hairy with matted wool; the leaf stalk is 2–2½ inches long, stout, densely hairy with matted wool.
Stems are gray to brown or black, downy when young, smoother and somewhat grooved when older; the ends of the vine usually die back a few feet during winter; tendrils are absent.
Bark is grayish brown, somewhat grooved, the ridges narrow, often peeling into strips; the wood is soft, somewhat pithy, and pale brown.
Flowers May–June, single, opposite a leaf on new growth. Flower stalks are 1–1½ inches long, stout, curved, hairy; flowers are 1–2 inches long, cylindrical, yellow or greenish yellow, densely hairy, the flower tube sharply curved, the throat almost closed; the calyx (tubular outer part of the flower consisting of fused sepals, though it seems like fused petals) with 3 lobes, bent backward, wrinkled, dark purple; petals are absent; stamens 6.
Fruits in September, a dry capsule, 1½–3 inches long, 1–1¼ inches wide, cylindrical, grayish brown, hanging, 6-sided, with many seeds compressed in vertical columns. Seeds about ⅜ inch long, flat, thin, triangular, grayish brown.
Similar species: Not counting cultivated, nonnative plants, Missouri has only two other members of the birthwort family:
- Only one of them, Virginia snakeroot (Aristolochia serpentariae), is in the same genus, but it is a nonwoody perennial plant, not a vine. It has alternate, entire leaves, and it usually has a rather zigzag stem that is 6–24 inches long.
- Our other member of the birthwort family is in a different genus; it is wild ginger (Asarum canadense), a spring woodland wildflower lacking obvious stems; low to the ground, it has hairy, kidney-shaped leaves and brown flowers with 3 lobes that bend backward.
Height: climbs on trees to 75 feet.
Mostly south of the Missouri River.
Habitat and Conservation
Occurs in bottomland and mesic (moist, rich) upland forests, usually associated with banks of streams and rivers, less commonly on open gravel bars, rarely on margins of sand prairies. Also occurs in open, disturbed, floodplain areas.
Woolly pipe-vine is a characteristic woody climber along streams and rivers in the Ozarks, where hikers and canoeists often don’t notice the plants because the leaves and flowers can be located high above in the treetops.
Relatively common in appropriate habitats. A native, high-climbing woody vine, mostly occurring in the southern half of the state.
This vine is often cultivated as an ornamental. The attractive heart-shaped leaves and interesting flowers and capsules make it one of Missouri’s most fascinating vines. The flowers are usually hidden among the leaves, but they are nifty nevertheless. As one of the principal food plants for pipevine swallowtails, it makes a great addition to a butterfly garden. It can also be used as a dense, living porch screen; you can have it climb on a trellis, arbor, fence, post, or wall. A native of streamside or bottomland woods, it needs rich, moist soil.
The genus name, Aristolochia, is a combination of two Greek words: áristos (“best”) and lokheía (“childbirth”). Therefore, the genus name somewhat matches the common name “birthwort” (birth plant). In ancient times, a European species of birthwort was used medicinally for some aspect of the childbirth process (pain or infections), in part because the flower shape was thought to resemble a birth canal or a fetus in a womb.
The sap of plants in the birthwort genus is yellowish and tastes bitter. Bruised plant parts emit a faint, unpleasant odor similar to that of turpentine. Various species have been investigated for the possible production of tumor-fighting chemical compounds. These same compounds have also been implicated as having carcinogenic properties.
The species name, tomentosa, refers to the tomentose, or densely woolly, matted hairs on the leaves and stems.
The common name Dutchman’s pipe refers to the shape of the flowers, which somewhat resemble the Meerschaum smoking pipes made in Europe. Meershaum is a lightweight, porous mineral that is an ideal material for the bowl of a smoking pipe. The corncob pipes made for over 100 years in Washington, Missouri, also have porous, gentle-smoking attributes and are named “Meerschaum” for their quality, as well as for the ethnic German heritage in the region. Some of Missouri’s corncob pipes have the basic hooked shape of this pipevine flower.
The pipevine swallowtail butterfly uses this and related species as its larval host plant. Females lay eggs on the leaves, and the larvae hatch and feed together on the leaf edges. Members of this the birthwort genus contain toxic aristolochic acids, and the pipevine swallowtail caterpillars are able to store the chemicals in their body tissues, making them unpalatable or sickening to predators.
Some nonnative species of birthworts, planted by gardeners, contain either higher amounts or different sorts of toxic chemicals, making them toxic or inedible to even pipevine swallowtail caterpillars. When a female swallowtail deposits her eggs on one of these plants, the caterpillars cannot eat the leaves and soon die.
A quick scroll through a photographic list of Missouri’s butterflies reveals several butterflies that resemble pipevine swallowtails: black, with hindwings dusted with iridescent blue plus a line of orange dots. Examples include the red-spotted purple, females of the eastern tiger swallowtail, spicebush swallowtail, and black swallowtail. For the most part, these species eat nontoxic plants and would be delicious to predators, but a predator that has been “educated” by trying to eat a pipevine swallowtail will not eat similar-looking butterflies. Therefore, all these types of butterflies are connected, directly or indirectly, to pipevine plants and their toxins.
The flowers of many birthwort species, including woolly pipe-vine, emit an odor similar to rotting meat, which attracts flies and gnats. Pollination in most birthwort species is a complex affair involving small flies that become trapped overnight in the expanded basal chamber of the floral tubes. Once the pollen is developed, the flower starts to wither, and the stiff, downward-pointing hairs in the narrower portion of the tube relax. This allows the insect to escape, but by this time it has been coated with pollen. After it departs the first flower, it is attracted to another stinky birthwort flower and pollinates it as it becomes trapped again.