Potential for physiological self-incompatibility in Heliconia bihai as a mechanism to promote outcrossing was studied in St. Lucia. Our results do suggest that H. bihai is self-compatible. However, plants vary in their degree of compatibility from full to partial self-compatibility. We found only traces of physiological incompatibility but conclusive determination of its mechanism would require further testing. In contrast to Central American Heliconia species, we found that more pollen tubes are able to grow inside H. bihai styles following artificial pollinations. Additional studies would be needed to test if other populations of H. bihai share this phenomenon.