USDA Soil Conservation Service
Grassy arrowhead
Sagittaria graminea

Grassy arrowhead (Sagittaria graminea) is an invasive plant. It is a native of Eastern and Central North America and was first detected in Washington State in 1994.

Grass-leaved Arrowhead is found in swamps in shallow water on both mud and sand. Where it has been introduced outside of its native range, it has become a serious pest plant.
Summaries of State Plant Protection Laws and Regulations
Washington