Friday, September 7, 2012
Spurred Butterfly Pea - Centrosema virginianum
Spurred butterfly pea (Centrosema virginianum) is the most common butterfly pea in Florida, occurring statewide in a variety of upland habitats. It is primarily a species of the Southeast, but specimens occur into the Midwestern state of Illinois and into the Eastern Seaboard as far north as New Jersey - where it is an endangered species.
Like other members of this genus, spurred butterfly pea is a perennial vine with a weak stem that winds its way through adjacent vegetation. It does not have tendrils, but coils its stem around neighboring plants to gets its flowers upright and above the ground. Each of these stems emerges in the spring from the base and may reach 6-8 feet in length.
One difference between this species and its much rarer relative (C. arenicola) is the leaf shape. Though variable, spurred butterfly pea tends to have narrower leaves. These leaves are comprised of three leaflets that are alternate along the winding stems.
Like all members of this genus, the flowers are a rich purple to light lavender, with a strongly keeled lower calyx lobe. Because the flowers open "upside down", this lobe is above the bifurcated upper lobe.
A white patch, striped with purple, guides nectaring insects to the nectar source beneath the keeled lobe above. The flowers occur mostly in summer and plants are in bloom for many weeks.
Spurred butterfly pea is an attractive wildflower that also serves a purpose in the butterfly garden. It is the larval food plant for long-tailed and northerrn cloudywing skippers. Despite this, I have not seen it offered historically by anyone associated with FANN - the Florida Association of Native Nurseries. In fairness, it is a difficult species to keep in a nursery because of its tendency to scramble everywhere and tangle itself in every adjacent plant nearby. It is easy to grow from seed, however, collected as the pea-like pods ripen and split. Spurred butterfly pea is tolerant of a wide variety of growing conditions, but should be kept on a fence or trellis in a small garden setting. If the planting is large enough, it could be allowed to vine on larger upright species such as goldenrods and blazing stars. If you see this species, you can also simply admire its beauty - and look for butterflies alightng on it to lay their eggs.