Crossvine (Bignonia capreolata) is an evergreen vine native to the southeastern United States which grows in sunny woodland edges and in clearings where it can get enough sun. It climbs pretty much anything except a solid surface using twining tendrils with holdfasts like suction cups on the ends. It is sometimes grown as an ornamental since it has showy orange trumpet-shaped flowers for a brief period in the summer that are attractive to hummingbirds.
In the summer, the leaves and stems are mostly green, however in the winter the undersides of the leaves and stems turn purple. It is a very common plant and really stands out when the woods are brown and barren in the winter. If foraging for this plant, it is very important not to confuse it with the red-flowered Trumpet Creeper (Campsis radicans) or Carolina Jasmine. Trumpet Creeper is called Cow Itch because it causes rashes and skin irritation in many people. Cow Itch fortunately looks quite different once you know what to look for, and is deciduous instead of evergreen. Carolina Jasmine is evergreen and highly toxic, but looks quite different. The key to identifying Crossvine with certainty is the cross-like stem arrangement. It has compound leaves with only two leaflets plus a modified leaflet that is a tendril, which are opposite each other.
The leaves themselves are what we are after for tea. Some of the Native American tribes of the southeast used crossvine for a number of medical uses. Knowledge about the plant was passed to African slaves but largely fell out of use. Tommie Bass learned of the plant and used it to get overworked, exhausted mules and horses back on their feet, then on similarly exhausted women, and among a few herbalists in the southeast it continues to be used as an adaptogen and to boost energy. (Yes, it works for men, too.) Given the uncommon use of this plant, it is unlikely any pharmaceutical trials will be performed on the plant, but we do know the plant contains reserpine. Reserpine reduces blood pressure and may reduce heart rate, and is used as an anti-pyschotic. From the International Journal of Pharmacognosy and Phytochemical Research 2012; 4(3); 89-91:
Subjective accounts of the effects of ingesting an infusion of three dried leaves of B. capreolata daily over three days describe it as energizing (this dose represents about 0.35g of dried leaf containing approximately 85 μg reserpine). While this is not necessarily a reported effect of reserpine administration, it is possible that alterations in sympathetic tone caused by reserpine could promote restfulness and feelings of rejuvenation. Still, it seems more likely that the unique effects of B. capreolata are due to a synergistic effect of reserpine and other, unidentified constituents.
So in a nutshell, it works, but we don’t really know why. Modest intake is suggested due to the potential side effects of reserpine. All the contraindications of reserpine apply: do not take if pregnant or nursing, if you have low blood pressure, or if you are on any blood pressure or anti-psychotic drugs.