Nothocalais cuspidata (Pursh) Greene (Asteraceae) is a plant species of conservation concern in Missouri; it typically occurs as isolated populations in hill and sand prairies which are themselves rare and fragmented habitats. The present study was undertaken to understand its reproductive biology as a hill prairie member and the possibility of reduced reproductive output in this isolated habitat. Nothocalais cuspidata is an early spring-flowering, nonclonal, primarily self-incompatible perennial that exhibits a 4 wk flowering phenology with most florets open to cross-pollination over a 2–3 wk period. The attractive UV reflective florets were visited by six species of halictid and solitary bees. The study population did experience depressed reproductive output in 2014 compared to 2004, with open-pollinated florets producing 19.1% fewer fruits than in 2004 along with a 37% decline in population size over a 13 y period. We suggest the depressed fruit production experienced is likely due to the unpredictable spring weather associated with early flowering and sporadic pollinator visitation in an isolated habitat leading to large variations in reproductive success over time or a reduction in compatible mating types as the population declines.