Butterflies & Swallow-worts

by Christa Hayes

It was a butterfly that guided me to my first encounter with Gulf Coast Swallow-wort (Seutera angustifolia*). Although a common plant along the edges of brackish marshes, this wisp of a vine is practically invisible to the unpracticed eye. I was driving along a short causeway pondering the movements a Queen butterfly (Danaus gilippus) over an expanse of Black Needle-rush (Juncus roemerianus). The Queen repeatedly disappeared into that inhospitable environment, reappeared, and sank again.

Animals do not waste energy; something of value to the butterfly was in that high marsh. I stopped, and discovered a narrow-leaved, blooming vine using the rapier stalks of rush as a trellis. Small umbels of waxy cream flowers drew Queens, Gulf Fritillaries (Agraulis vanillae) and Salt Marsh Skippers (Panoquina panoquin) in to nectar. The high marsh was not quite the barren place I had imagined.

Gulf Coast Swallow-wort


Gulf Fritillary

Salt Marsh Skippers

Queen caterpillar feeding on Gulf Coast Swallow-wort

Gulf Coast Swallow-wort is one of a suite of plants that thrive along the edge of brackish marshes. Queen butterflies use them as the host plant for their caterpillars. Gulf Coast Swallow-wort is related to milkweeds (Asclepias sp.), which serve as host plants for the closely related Monarch butterfly (Danaus plexippus). Ideal conditions for a successful Queen Butterfly life cycle call for near by shrubs and trees, such as baccharis (Baccharis angustifolia; B. halimifolia), marsh elder (Iva frutescens), southern red cedar (Juniperus virginiana var. silicicola) and palms (Sabal palmetto). These larger plants provide structure and safety for the Queen’s chrysalis.

* The scientific names for many species change over time as technology improves and biologists have new tools to sort out family relationships. Your identification books and some web sources may still use Seutera angustifolia’s previous name, Cynanchum angustifolium.

Photographs by Christa Hayes & Arden Jones