Know Your Natives – Trumpet Vine

Trumpet Vine or Trumpet Creeper (Campsis radicans) of the Trumpet Creeper (Bignoniaceae) family is a non-twining, tendril-free, woody vine with spectacular, large, orange to red, trumpet-shaped flowers. The genus name is Greek for “curved,” a reference to the curved stamens. The specific epithet is from Latin for “taking root” in reference to the aerial rootlets that bind the climbing plant to its host. In the U.S., Trumpet Vine is native from Oklahoma and eastern Kansas to the Atlantic and Gulf Coasts as well as in scattered areas in Texas. Naturalized occurrences extend west and east across the country to as far as Washington State and Vermont. In Arkansas, the species is recorded from every county. Habitats include a wide variety of soils in sun and shade: well-drained to moist woodlands, woodland edges, fields, rights-of-way, fences and fencerows. Vines not only climb, they trail along the ground, sprawling and clambering over themselves and other plants and structures.

Mature plants in sunny sites produce two growth forms: trailing, fast-growing, limber to woody, non-flowering vines to 25+ feet long that grow along the ground and over other plants and structures, often producing terrestrial and aerial (clinging) roots at the nodes. And rigid to woody, somewhat self-supporting, arching vines to 6+ feet long that extend outward from these vegetative stems. Depending on space, sunlight, and presence of supporting objects, a plant may develop into a wide-spreading, dense, elevated groundcover and/or an aggressive liana climbing trees, fences, and even buildings. Wide-spreading woody roots may produce ascending suckers well away from a plant’s point of origin.

Photo 1: This growth form is a sucker from an established plant that will not produce a terminal inflorescence in the current year.
Photo 2: Vegetative stems, when in near-contact with soil or vertical objects, may develop aerial roots at nodes along their lower surface. (As shown, vine is inverted).
Photo 3: In this sunny site, multiple stems did not attach to surrounding rocks during their first growth-year and have become woody in their sprawled positions.
Photo 4: On this steep slope, intermixed stems form a dense ground-cover that is several feet thick.
Photo 5: The main trunks of this vine are at the back wall of the building. Thick growth has extended around the corner and onto the roof.
Photo 6: This vine has reached the top of this 70-foot Short Leaf Pine. On inset photo, asterisks indicate section of tree shown by main photo. At ground level, the single “trunk” has a diameter of 5 inches.

Old plants, established at the base of large trees, tend to have one to a few trunks which may grow to 3-5 inches in diameter. As vines age over multiple years, the bark exfoliates in narrow strips and becomes moderately fissured.

Photo 7: Aerial roots of this vine have deteriorated but the vine remains firmly fixed in a vertical position. Larger vine is 2½ inches in diameter. Leaves are those of Poison Ivy (Toxicodendron radicans), a common cohort of Trumpet Vine on the same host.
Photo 8: The four upper stem-segments, of the current growth-year, are from a 6-foot-long vine, aging from right to left. Segment at lower right is from a 20-foot long vegetative vine which had the same appearance its entire hardened length. Segment at lower left shows an axillary pair of current-year branches. (Leaf blades removed.)

Current-year vines bear widely spaced, decussate, opposite, odd-pinnately (with a single terminal leaflet) compound leaves. Leaflets are ovate to broadly lanceolate with rounded to cuneate base and long-acuminate to acute apex. Leaves have 7-13 leaflets, shiny, dark green, and glabrous above and dull, yellowish green, and minutely pubescent beneath. A 7-leaflet leaf may be 7 inches long (including a 1½ inch petiole) and 4½ inches wide with leaflets that are to 3 inches long and 1½ inches wide. Petioles may have a half-dozen tiny nectary pits along their swollen bases. Leaflet margins are coarsely serrate. Terminal leaflet blade is symmetric while lateral leaflets tend to have oblique bases.

Photo 9: Display of leaves: Upper pair from mid-vine, middle pair from beneath the terminal inflorescence, and lower pair from a short axillary branch. Upper-left leaf is 7 inches long and 4¼ inches wide.
Photo 10: Upper surface of leaves is shiny dark green, the lower surface pale green with white pubescence. Venation is pinnate. Tertiary veins form a reticulate pattern. Terminal leaflets shown.
Photo 11: Bulging bases of petioles have pores that provide nectar to ants and other insects. Petioles are slightly grooved. Dormant axillary buds are covered with brown scales.

Flowers, from June into August, first appear as small ovoid buds. The terminal, cymose inflorescence bears opposite pairs of stubby peduncles that produce pairs of short, stubby branches. Each branch bears a simple cyme of three flowers, one terminal and a pair of laterals, with the terminal flower blooming first. Often, pedicels or flower buds abscise so that compound cymes become knobby. Plants in full sun flower more profusely.

Photo 12: Early green flower buds are tightly protected by their calyxes; these become orange with approaching anthesis. Calyxes have five triangular lobes which meet in bud to form a distinct point. Ants (shown) feed on nectar from pores on the calyx.
Photo 13: Display of a single compound cyme while in bud, separated into simple cymes with 3 buds each. Buds often become dislodged or are eaten, as shown by two cymes at upper right with only 2 buds.
Photo 14: Terminal inflorescences are subtended by a pair of small leaves. Within an inflorescence, indistinct nodes at the base of peduncles, branches, and pedicels are subtended by a pair of opposite, appressed bracts.
Photo 15: A vine may have multiple compound cymes forming a single terminal cluster. Here, subtending leaf pairs have been partly removed at asterisks. Cymes become knobby as some buds and flowers drop off.

In bloom, the calyx of Trumpet Vine flowers is orange, the corolla outwardly orange to reddish. The flowers are spectacular and the vines cultivated worldwide for their decorative appeal. The corolla is slightly irregular, that is, bilaterally symmetrical. The tube measures about 3 inches long and tapers from about an inch at the tip to ¼ inch within calyx. Prominent red nectar guide-lines extend upward within the yellowish interior of the tube. Corollas remain open for a single day, after which, the entire corolla (and the stamens attached to the tube within) is shed, often littering the ground with color beneath high-climbing vines. Flowers are a favorite of bumblebees, sphinx moths, and hummingbirds.

Photo 16: Some vines have flowers that are more reddish. Flowers are oriented in various directions.

Flowers have 4 functional stamens (filament + anther) and 1 sterile, vestigial stamen or staminode, the filaments attached not to the receptacle but to the inner wall of the corolla tube. The curved, sturdy, pollen-producing stamens are in two pairs of two lengths. Just within the mouth of the corolla, anthers and stigma are pressed against the upper surface of the tube, perfectly positioned to deposit pollen on and to receive pollen from the heads and bodies of pollinators as they enter the tube for nectar.

The 2-chambered, superior ovary is borne on a prominent, nectar-secreting disc. The pale-green style terminates with a flat, folded stigma which, when receptive to pollen, spreads wide into 2 thin, flaplike lobes (⅛ x ⅛ inch) to expose stigmatic surfaces. In addition to outcrossing by cross-pollination, self-pollination commonly occurs. With sufficient pollen load, the active stigma flaps press together.*

Photo 17: Stamens and style/stigma are pressed against the roof of the tube. As shown, the two flaps of the active stigma (above the anthers) are closed. Anthers and stigma are not exserted beyond the corolla tube. Minute white pubescence can be seen around the orifice. Corollas are slightly irregular.
Photo 18: Flowers have 2 pairs of functional stamens, a staminode, and a single pistil. Straight red nectar guides extend up along the yellow tube interior. As shown, style (pale green) and staminode are centered between the 2 stamen pairs.
Photo 19: Within a single cyme, the terminal flower blooms first. Pistil (this one is 2¼ inches long) consists of a nectar-secreting, stump-like stalk below a superior ovary, a long style, and a bilobed, flap-like stigma.
Photo 20: These anthers sacs have dehisced and pollen has been released. The closed flap-like stigma is positioned behind the distal anthers.

Fertilized flowers produce a large, bean-like capsule, green at first and eventually tan. Of the many flowers in a large inflorescence, few flowers produce capsules. Mature capsules, to 3-6 inches long and 1 inch wide, are straight to slightly curved, with an opposite pair of prominent, longitudinal ridges that mark the sutures. Capsules open at the sutures by two valves. A septum, perpendicular to the valves, supports a pair of placentas in each of the 2 chambers at the junction of the septum to the capsule walls. Being thick-walled and packed tightly with numerous seeds, the bulging capsules are heavy and pendulous on the vine. Exterior of capsules is smooth and glabrous with a few scattered pores that provide nectar to ants. Dry, woody capsules persist well into winter as the valves slowly dehisce to release layers of thin, flat seeds. The airborne seeds with translucent wings measure about ⅝ by ¼ inch. The gaping valves of empty capsules remain on vines into spring.

Photo 21: Curved, pendulous capsules and ascending flowers often occur on the same compound cyme. Unfertilized flowers quickly drop off at the pedicel so that stubs remain. Styles of fertilized flowers persist for a short time.
Photo 22: Developing seeds are tightly packed. The septum (see arrows) is positioned perpendicular to the ridged sutures. Placentas (see asterisks) are at the junction of the septum to the capsule walls. Note pores on capsule.
Photo 23: This dry, firm, thick-walled capsule is 4¾ inches long and ¾ inch wide. Numerous thin, winged seeds are stacked within the two chambers. The now-thin, flat septum extends the length of the capsule.

Although Trumpet Vine has attractive leaves and especially showy flowers, the plant is probably too large and aggressive to be added to most gardens. With continuous pruning and removal of rooted suckers, plants have the potential to be attractive on arbors and trellises. In sunny sites, the plant’s tangled and dense growth habit can provide erosion control and nesting sites for birds as well as protection for birds and small mammals. Plants are less vigorous in more shaded sites and produce fewer flowers. Trumpet Vine is a great plant for hummingbirds. Vines attaching to walls and roofs can cause damage. For some people, sap can cause skin irritation.

The only other species in the genus Campsis is Chinese Trumpet Vine (C. grandiflora), a native of Eastern Asia––and the two species are an example of what plant geographers call the Chinese-American disjunction. (The two species worldwide of Liriodendron are another example of this intriguing distribution pattern.) In the U.S., Trumpet Vine may be confused with another, closely related, high-climbing, woody vine, Cross Vine (Bignonia capreolata). However, Cross Vine has tendrils, 2-leaflet compound leaves and, typically, reddish tubular flowers with lobes that are yellow on the inside.

* For a detailed study of pollination, see: https://www.jipb.net/EN/Y2004/V46/I9/1071

Article and photographs by ANPS member Sid Vogelpohl

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