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Weed Identification

seaside arrowgrass



Scientific Name

Triglo maritima

Other Common Names:

long arrowgrass

Synonyms (former Scientific Names):

Triglochin maritimum var. elatum
Triglochin elata
Triglochin elatum


Prefers moist alkaline soils, this plant has a sturdy rootstalk with many fibrous roots. The stems which emerge from the same point as the leaves, can reach as tall as 100 cm and the previous year's leaf bases are usually present.


This plant has grass-like, basal, fairly fleshy leaves. Leaves may reach 50 cm tall and 6 mm wide are dark green in color and cross-sections are usually semi-circular. Each plant will have 4-10 leaves emerging from the previous year's growth.

Identifying Characteristics

Fairly fleshy grass-like basal leaves, small greenish-white flowers, prefers moist alkaline soils. This plant is also toxic, it contains triglochinin and taxiphillin that release hydrogen cyanide when ingested, resulting in respiratory failure.

Flower Seed Head

1-2 mm wide greenish white flowers arise from the terminal spike cluster. The pistil has feathery stigmas to collect pollen from the wind.

Seed Fruit

Flowers produce 3-6 capsules 6mm long each containing a single seed. Seeds are yellow-brown elliptical 3mm long by 0.5mm wide. Each plant is capable of producing 600 seeds.

Where Found

Throughout Canada and the United States in moist alkaline Soils.

Life Cycle


Plant Type