A beautiful native wildflower welcoming visitors to the beaches of South Padre Island this summer is the ground-hugging, pink-to-purple species of morning glory, Ipomoea pes-caprae, better known as the railroad vine. This common name, though not picturesque, reflects the plant’s tendency to grow its leaves in long, straight, running vines up to 100 feet long across the dunes and back beach, resembling railroad tracks to those with vivid imaginations.
The railroad vine is an extremely important member of the coastal dune community. It is one of the first plants to colonize active dunes, stabilizing them and helping to prevent them from blowing away into the Laguna Madre. It provides a fixed, binding environment for other plants to gain a toehold. Ripened seeds from mature railroad vines are blown into the Gulf and then ride along on ocean currents until they are washed up on beaches and deposited above the high tide line. Here they germinate and quickly grow, sometimes forming dense mats, giving life to the wind- and wave-tossed sand. Such vegetated dunes are critical for preventing coastal erosion, particularly on barrier islands like South Padre.
Preserving the natural coastline as much as possible has gained significance with rising sea levels and consequent breaking waves reaching higher up the beach.
Not only is the railroad vine a tough pioneering species, but it can also withstand the harsh punishment of extreme coastal weather events. The plant’s taproot can grow to a depth of three feet, helping it hold firm during summer’s harsh tropical storms and winter’s strong desiccating north winds, which can scorch and damage the vines and leaves.
After enduring severe weather, the above-ground part of the plant may appear dead, but its deep taproot soon nurtures the formation of fresh leaves and vines, allowing it to resume its rapid growth, which can measure up to 10 inches in one day. Because the railroad vine has such a high tolerance for sun, heat, wind, and salt spray, and thrives in an environment with poor soil nutrients, shifting sands, and little water, this creeping perennial flourishes on all of SPI’s beaches as well as in most subtropical coastal environments around the world.
Railroad vines may bloom during any month of the year, but they flower most prolifically in the warmer months of spring through fall. Each individual trumpet-shaped blossom lasts only for one day. If you want to see this island beauty in its full glory, you will need to be on the beach early in the morning. True to another of its common names—beach morning glory—the blossoms open in the early morning and close again as temperatures climb.
When this happens, it is a good cue to leave your sandals above the high tide line and enjoy the refreshing Gulf waters!
