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Arabis missouriensis Greene

Photo: Missouri Rockcress in flower

Missouri Rockcress

Habitat: Circumneutral bluffs, ledges or rocky woods. [Rocky summits and outcrops (non-forested, upland); Hardwood to mixed forest (forest, upland)]

Range: Quebec to Ontario, as far south as Georgia and west to Oklahoma.

Photo: Basal rosette of Missouri Rockcress

Aids to Identification: Missouri rock-cress is one of several similar rock-loving plants belonging to the Mustard family. It is a stiffly upright plant, growing 20-50 cm high, with narrow, upward-pointing stem leaves and a basal rosette of broader, toothed leaves. It bears an elongated cluster (raceme) of 4-petaled white flowers up to 2 cm in diameter. These strictly upright flowers develop into narrow, drooping pods 5-8 cm in length. The stem is not glaucous and bears many leaves.

Photo: Missouri Rockcress in fruit

Ecological characteristics: Found on ledges and in rocky woods.

Phenology: Flowers in June.

Family: Brassicaceae

Synonyms: Known as Boechera laevigata (Muhl. ex Willd.) Al-Shehbaz. Referred to as Arabis viridis Harger or Turritis laevigata Muhl. ex Willd. in some very old treatments.

Known Distribution in Maine: This rare plant has been documented from a total of 6 town(s) in the following county(ies): Cumberland, Oxford, York.

Dates of documented observations are: 1905, 1996 (2), 1997 (2), 2000 (4), 2001 (3)

Photo: Basal rosette of Missouri Rockcress

Reason(s) for rarity: Reaches the northern limit of its range in Maine.

Conservation considerations: Effects of logging have not been documented, but partial removal of the canopy may mimic natural conditions as the plant tends to grow in rocky openings in the woods.