First report of fasciation in Pitcher's Thistle, Cirsium pitcheri (Asteraceae)

Abstract

We document the first reported occurrence of fasciation in the federally threatened Pitcher’s thistle, Cirsium pitcheri (Asteraceae). In 2013, we discovered two adult plants of Pitcher’s thistle out of a total of 176 plants at West Beach, near Miller, Indiana, USA, that exhibited both normal and fasciated growth. Unlike plants with normal growth, a portion of the upper stems of these plants was flattened, and some flower heads were elongated into a fan-like shape. Each plant had one large fasciated terminal seed head and several less severely fasciated ancillary heads. The fasciated terminal head on one of the plants found produced an estimated 1153 seeds, whereas normal terminal heads typically produced 80 ± 9 viable seeds. The cause of this fasciation is unclear, but may be due to infection with phytoplasma