Geranium robertianum is an annual or biennial herb, to 60 cm tall from a taproot, stems weak, branched, spreading, hairy, often red, strongly scented; roots sparsely or facultatively associated with VA mycorrhizas (Brundrett and Kendrick 1988).
Leaves alternate, palmately divided to base into 3-5 segments, the center segment stalked, all segments lobed or divided, tips rounded; becoming red in autumn.
Flowers rose-purple, about 2 cm wide, 5 petals widest near top, base narrow, sepals 0.7-0.9 cm long tip with short beak; flowers usually in pairs from upper axils; blooms and fruits May-Oct.
Fruit dry, linear above, 1-seeded carpels cupped in persistent calyx.
Wetland status: UPL.
Frequency in NYC: Very infrequent.
Habitat: Dry woods.