Yellow passionflower (Passiflora lutea) of the Passifloraceae (Passionflower) Family is found in the US from Texas to Kansas to Illinois and eastward to the coast. In Arkansas, it is found throughout the state. Yellow passionflower is more delicate in appearance and less aggressive than purple passionflower. The species grows in moist bottomland and upland forests to medium-dry, rocky upland woodlands and thickets, doing well in bright shade or partial sun.
Yellow passionflower is a small, unbranched herbaceous perennial vine with trailing, climbing or sprawling stems up to fourteen feet long (but often encountered a few to five or six feet long). New vines can grow upright for a couple of feet on their own before gravity wins out, unless support can be found on other vegetation. The number of vining stems increases from year-to-year near its original location, generally not spreading widely underground like its larger, showier cousin. One or more tendrils and/or flowers arise from each leaf axil. Tendrils typically exhibit a spring-like appearance. As vines mature, the lower leaves drop off.
Alternate leaves, dark green on top and light green below, consist of three smoothly rounded, shallowly cut lobes with entire (no teeth) margins. Each lobe is centered by a primary vein. Lateral veins, which are slightly arcuate, arise at about a 50o angle off the central veins. The three primary veins terminate just slightly past the leaf margin. Leaves, from 2½” to 6” wide and 2″ to 4½” long, may be strongly mottled with irregular lighter green areas, but tend to become more uniform in color with maturity. Leaves are generally spaced from one to two inches apart along the stems, with spacing decreasing in brighter light. Multi-stemmed plants in bright light can have a dense layer of leaves floating above the stems.
Photo 1: Leaf and tendril of yellow passionflower. With maturity, leaf patterns (if any) may fade.
Flowering of yellow passionflower occurs in May to July. Flower buds are elongated and squared-off and indented at the stem end. Flowers are a light greenish yellow (“lutea” is Latin for yellow). The structure of the perianth, corona and reproductive portions of flowers of yellow passionflower are very similar to those of purple passionflower, however, parts are significantly smaller, with total flower diameter only about one inch. Whereas sepals and petals of purple passionflower are of about equal width, petals of yellow passionflower are narrower than the sepals.
Photo 2: Yellow passionflower bud and flower. Note broad sepals and narrow petals.
Photo 3: Flower structure as seen from the side. Note spring-like tendril in foreground.
Flowers are followed by small, round and smooth green fruits (berries) on long, thin stalks such that the fruits dangle from the stems. Seeds, up to 10 per fruit, are each surrounded by a membrane filled with liquid. Upon ripening, fruits become dark bluish purple with a whitish haze. Ripe fruit is soft and releases a staining purple liquid when squeezed, the membranes having disintegrated. Dark brown seeds, about 0.15” long and half as wide, have points at both ends and a textured surface.
Photo 4: Mature fruit on five or more intertwined stems of yellow passionflower supported on eastern redcedar. Dried flower parts persist on the fruits.
Photo 5: Seed of purple and yellow passionflower for comparison. Note characteristic texture of each.
Yellow passionflower is an interesting plant in a garden or natural area. The leaves, tendrils, flowers and fruit all add interest. Its rambling but sparse growth habit allows it to drape over other plants without any particular effect to other plants. This plant, attractive to bees and small wasps, is the only pollen source for the solitary ground-nesting Passionflower Bee (Anthemurgus passiflorae). Along with purple passionflower, yellow passionflower is also a larval host plant for the Gulf fritillary butterfly. Wildlife eat the fruit and disperse the seed.
Photo 6: Gulf Fritillary caterpillar on purple passionflower (Passiflora incarnata) leaf.
Photo 7: Adult Gulf Fritillary butterfly on blue sage (Salvia azurea).
Article and photographs by ANPS member Sid Vogelpohl