California arrowhead  (Sagittaria montevidensis)

California arrowhead, an annual aquatic broadleaf, is found in wet areas throughout California's Central Valley, San Francisco Bay regions, and the central South Coast up to an elevation of 100 feet (300 m). It is a native species that is a common weed in rice fields and irrigation canals. Although weedy in some situations, its fruit and leaves are an important source of food for waterfowl in natural ecosystems.

Seedling

Leaves are narrow, succulent, light green and taper to a blunt point. Rectangular markings on leaves distinguish it from ducksalad, river bulrush and ricefield bulrush. The characteristic arrowhead leaf-shape appears with the third or fourth true leaf. Submersed seedlings look similar to Gregg arrowhead.

Mature plant

Leaves and flowering stems grow up to roughly 1.5 feet (0.5 m) tall. Plants grow in groups and exist both under and above water but most are above water. The leaves may vary a lot in size and shape but most exposed leaves are arrow shaped, and have two pointed lobes pointing backwards giving the the leaves the arrow shape. Gregg's arrowhead, a similar species, has much narrower and longer basal lobes.

Flowers

Flowers bloom from June through September. The flower stalk is shorter than the leaf length. Flowers have three white petals with a green-yellow coloring at the base of the petals. There are three flowers at all nodes, except the lowest node, which has two (rarely three) flowers. Unlike California arrowhead, Gregg's arrowhead has three flowers at the lowest flowering stem node.

Related or similar plants

• Ducksalad, Heteranthera limosa
• River bulrush, Scirpus fluviatilis
• Ricefield bulrush, Scirpus mucronatus
• Gregg arrowhead, Sagittaria longiloba

More information

• Broadleaf ID illustration
• Calfloraâ??s s distribution map
• For agriculture: UC IPM Pest Management Guidelines