Watercress
Nasturtium officinale
(Rorippa nasturtium-aquaticum)
Photographed in Rackensack Canyon, Maricopa Co., Arizona, USA. April 2008.
ANNUAL: An aquatic annual found growing along mostly semipermanent
waterways or close to springs. Plants rarely rise more than
8cm above the water surface.
LEAVES: Leaves are pinnately compound with five or so leaflets. Margins
are normally wavy-toothede. Young stems and leaves are edible - waterborne
parasites like giardia are a concern however.
RANGE: Introduced and widely cultivated; widespread in wet habitats
across North America. Restricted to wet places the Sonoran Desert in Arizona
and Mexico at springs and along flowing canyon bottoms.
FLOWERS: Many, compact flowers on mostly short spikes. Four white
petals.
FRUIT: An oblong capsule with two rows of seeds.
UNARMED.
Several Sonoran Desert butterflies have adapted to using this plant as a larval host. These include the Sara Orange-tip (Anthocharis sara) and the Checkered White (Pieris protodice).