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collage of Purpletop and Johnsongrass

Purpletop (Tridens flavus) vs. Johnsongrass (Sorghum halepense)

Updated November 16th, 2022

These two species are frequently confused where their ranges overlap. Both are perennial, warm-season grasses with purple inflorescences. They are easily distinguished by foliage, size, and details of the inflorescence. Although their habitats overlap, Johnsongrass is more restricted to moister, richer sites, and is more competetive with other vegetation, whereas purpletop ranges farther into drier sites and poorer soils and prefers less competing vegetation. Johnsongrass ranges farther west into arid climates, but their ranges in the east are similar.

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