Spartina anglica is a textbook example of a natural amphiploid, which originated from hybridization between S. alterniflora and S. maritima. Which of these species was the maternal parent has remained a mystery. Inheritance of chloroplast DNA in most angiosperms is strictly maternal and can thus be used to test the parentage of hybrid taxa. The DNA sequence of the chloroplast leucine tRNA gene intron was used to show that the introduced North American S. alterniflora is the female parent of the F1 hybrid S. x townsendii and the amphiploid S. anglica. A possible scenario for their origin is given.