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Delta Arrowhead (Sagittaria platyphylla) Classification, Uses, Removal

Sagittaria platyphylla, commonly referred to as Delta arrowhead, is a perennial aquatic plant that can reach heights of approximately 1.5 meters when fully grown.

Delta arrowhead has two types of leaves, one held above the water and the other submerged under the water. 

The plant inhabits wetlands, shallow lakes, marshes, ponds, and slow-moving waterways.

Scientific Classification

  • Kingdom: Plantae
  • Phylum: Magnoliophyta
  • Class: Liliopsida
  • Subclass: Alismatidae
  • Order: Alismatales
  • Family: Alismataceae
  • Genus: Sagittaria
  • Species: Sagittaria Platyphylla
  • Other Names: Broad-leaf arrowhead, Delta duck-potato, Ovate leaf arrowhead, and Slender arrowhead

Nativity and Distribution

Sagittaria Platyphyllais is native to the Eastern United States, Mexico, and Central America. The plant is also found in the following areas:

  • Australia
  • China in the Yangtze River Basin
  • South Africa

Physical Appearance

Delta arrowhead has arrow-like green leaves and white monoecious flowers
Delta arrowhead has arrow-like green leaves and white monoecious flowers. Image: Canva/nnhering
  • Flowers: White flowers that appear in 3-9 whorls. 
  • Leaves: Dark green leaves in color. 
  • Stem: They appear triangular in cross-section and slightly winged towards the base.
  • Fruits: Spherical clusters of fruits composed of numerous single-seeded fruitlets.
  • Roots: Has rhizomes, thus allowing the plant to colonize new areas.

Delta arrowhead flowers are monoecious (male and female flowers are produced on the same plant). 

The whorls of the male flower are at the top, while those of the female flower are at the bottom. Each flower has three green sepals and three white to pinkish petals.

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The plant’s flowering takes place primarily in the summer and fall seasons.

The submerged leaves of Sagittaria platyphylla are strap-like, measuring 10-50 cm long and 3cm wide, and have visible longitudinal veins. 

The emergent leaves are lance-shaped and are up to 28cm long to 10cm wide. The leaf blades are elongated or narrowly egg-shaped, with entire margins and pointed tips. They are smooth to the touch and shiny.

The plant’s fruits are oblong, measuring 1.5-3 mm long and 5-15 mm in diameter.

Life Cycle/Reproduction/Dispersal

  • Life Cycle: Perennial
  • Seeds: Brown, oblong shape, flattened with a small projection at one end.
  • Climate: Thrives in temperatures of between 68 to 95 degrees Fahrenheit.
  • Dispersal: Seeds are dispersed by birds, water, and wind.

Delta arrowhead reproduces through seed production and underground tubers and stem segments regrowth.

The underground stem fragments and tubers can be easily dispersed by water and various human actions, thus enabling the lateral expansion of the plant’s colonies over time. 

In sexual reproduction, the achenes (small fruits) are dispersed by humans, animals, birds, and water and take root in different locations.

Uses

The plant has visually appealing leaves and growth patterns and thus has been grown for decorative purposes.

Environmental Impact

The weed forms dense mats that block flow in shallow bodies of water
The weed forms dense mats that block flow in shallow bodies of water. Image: oklahomabiologicalsurvey

Blocks Water Flow

    The delta duck potato rapidly spreads and forms dense mats across shallow bodies of water, significantly obstructing water movement and causing sediment buildup. 

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    This can exacerbate flooding issues which could potentially trigger soil erosion on a large scale, leading to minor off-site consequences.

    Competes With Native Plants

      Sagittaria platyphylla impacts native ecosystems by vigorously competing with native water plants and impedes the movement of native fish.

      Water Pollution

        As the decomposing plant matter breaks down, it can consume oxygen from the water, decreasing dissolved oxygen levels. This can create hypoxic or anoxic conditions, which can harm aquatic life.

        In addition, the plant’s decomposing matter can heighten the risk of increased microbial action in the water and the growth of algal blooms, which produce toxins harmful to aquatic animals and humans.

        Control

        The following methods will control Sagittaria platyphylla:

        Chemical Control

          The following herbicides are effective in controlling the delta arrowhead:

          • Imazamox: A systemic herbicide absorbed and transported throughout the target plant. Its mode of action is slower but more comprehensive.
          • Imazapyr: A herbicide that inhibits the plant enzyme acetohydroxyaced synthase (AHAS), vital for plant growth and development. 
          • Glyphosate: A broad-spectrum, systemic herbicide, meaning it is absorbed into the plant and moves throughout to kill the entire plant, not just the parts sprayed.
          • Bispyribac-sodium: A water-soluble powder packaged in individual packets. To use it effectively, each packet should be mixed thoroughly with water before being sprayed or injected into the target plants.
          • 2,4-D compounds: Systemic herbicides absorbed by the plant and then move throughout the plant’s tissues to reach the site where they exert their herbicidal effects.
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          Mechanical Control

          This is done by winter plowing streams, lake beds, and canals after the rhizomes and tubers are exposed to frost and desiccation. 

          Although this method is effective for site-based eradication of the weed, it is only suitable for small infestations.

          Biological Control

          Australian authorities approved the release of the weevil Listronotus appendiculatus to biologically control Sagittaria platyphylla in the country.