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Pest Information

Water Arum

Water Arum

  • Latin Name: Calla Palustris
  • Common Name: Water Arum
  • Other Names: Wild calla lily, American cowslip, marsh arum, marsh marigold, yellow marsh marigold, water dragon

Pest Details

Water Arum
Water Arum
Water Arum


Native to North America, and found in the northeastern U.S. from Maine to North Dakota, and north through Canada to Alaska.


A perennial aquatic plant that reproduces from seeds and can spread by its vegetative parts. It is a floating plant found along the edges of lakes, ponds, marshes, or streams and ditches, forming dense mats over wide areas. Growth often extends up onto the banks of these habitats. Plants contain calcium oxylate crystals which, when eaten, cause severe pain in the mouth.


Mature plants form mats that may be about one foot in height. Plants are essentially without stems, but thick, fleshy stalks arise from the base and terminate with the large, dark green, fleshy leaves. These are smooth and heart-shaped with an extended pointed tip, and may be over 6 inches in length. The flower occurs on a similar, long fleshy stalk, and is essentially a single large concave petal about 3 to 4 inches in length, enclosing the huge, developing seed pod. The flower is yellow to white, and the seed pod is a compact grouping of several dozen seeds.

Characteristicts Important to Control:

Where control is needed plants can be physically removed, or they may be killed using a systemic herbicide. When growing in water ensure that the product used is labeled for aquatic uses.

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