Delta arrowhead

Sagittaria platyphylla

Family: Alismataceae

Other Scientific Names:

Sagittaria graminea Michx. var. platyphylla, Sagittaria mohrii

Weed class: A
Year Listed: 2026
Native to: South Eastern United States
Is this Weed Toxic?:

Not known to be

Legal listings:

This plant is also listed on the Washington State Prohibited Plants/Quarantine List. For questions about the quarantine list, contact the Washington State Department of Agriculture's Plant Services Program at (360) 902-1874 or email PlantServices@agr.wa.gov.

Why Is It a Noxious Weed?

Delta arrowhead is a highly invasive aquatic weed in Africa, Australia, Asia, and Western North America. In waterbodies, it outcompetes desired vegetation, hinders recreation, and reduces wildlife habitat. It floats easily to new sites and can heavily impact drainage and water infrastructure.

How would I identify it?

General Description

Delta arrowhead is a perennial, herbaceous, aquatic plant, which can emerge by up to a foot from water surface.

Flower Description

Clusters of 3 petaled white flowers grow on bright green stems above the water in the summer. At the center of the petals are yellow stamens or bright green fruits beginning to form. Each cluster of flowers has 3 to 9 flowers.

Leaf description

Leaves can be submerged below the water and can emerge arching above the water. The underwater leaves can be lance to arrow shaped, while the above-water leaves are never arrow-shaped.

Fruit Seed Description

The bright green seed heads break into several thin brown seeds as they mature.

May Be Confused With

There are several species of Sagittaria, Alisma, as well as Damasonium californicum and Vallisneria americana that delta arrowhead can look like.

Alisma spp.: Inflorescence branches multiple times (i.e., a panicle). Achenes are arranged in a ring, not a round fruiting head. Roots are not segmented. Leaf blades are often slightly heart-shaped at the base (i.e., cordate). Leaves are generally shorter than Sagittaria spp.

Sagittaria spp.:
S. cuneata and S. latifolia: Typically have arrow-shaped leaves. Pedicels curved upwards (ascending). Stamen filaments not pubescent. Native to Washington; common.
S. rigida: Fruiting heads sessile (distinguishes this species from all other Sagittaria spp. in Washington). Inflorescence stems often curved.
Occasionally with arrow-shaped leaves, but lobes are much smaller than those of S. cuneata and S. latifolia. Introduced to Washington; isolated populations
S. graminea: Fruiting pedicels typically straight or curved upwards (ascending). Pedicels for male and female flowers generally of similar thickness. Produces rhizomes. Does not produce stolons or corms. Class B Noxious Weed; isolated populations in Snohomish and Mason Counties

Damasonium californicum: Distinct fringed petals and star-shaped fruiting head. Threatened species with limited distribution in Washington

Vallisneria americana: Fully submersed species. Does not produce emergent leaves or flower stalks above the water’s surface. Leaves have a shiny center stripe. Distinct spiral fruit stalk produced underwater later in season

Where does it grow?

Delta arrowhead grows along the shallow margins of lakes, ponds, streams, rivers, and man made drainage and irrigation channels and ditches.

How Does it Reproduce?

Asexually via stolons. Chunks of plant can float to new sites. Also grow from seed.

How Do I Control It?

Manual

Hand pulling works on small infestations, when all plant parts, including roots, are removed from the water.

Mechanical

Excavation machinery is being used to remove large infestations of delta arrowhead in Australia.

Cultural

Making water deeper or entirely drying an area can be effective.

Biological

Future biological agents are being researched in other countries, but no species are approved for release in the United States.

Chemical

When considering using herbicide in and near aquatic and wetland sites, make sure you have the correct pesticide certifications, permits, and are using herbicides that are labeled for aquatic use.