Prostrate knotweed

Polygonum aviculare, Polygonum heterophyllum

Polygonum aviculare, commonly known as common knotweed or prostrate knotweed, is a low-growing, herbaceous annual plant belonging to the Polygonaceae family. This species is widely distributed and can be found in various habitats, including lawns, gardens, fields, and disturbed areas. Here's an informative description, including detailed information on its appearance, identification, and management:

Appearance:

  1. Growth Form:

    • Common knotweed is a prostrate, spreading annual herb that forms dense mats on the ground.

  2. Leaves:

    • The leaves are lance-shaped and alternately arranged along the stems.
    • Leaves have a distinct reddish-brown spot (ocrea) where they meet the stem.

  3. Flowers:

    • Small, greenish-white to pinkish flowers are produced in compact, spike-like clusters at the leaf axils.

  4. Stems:

    • Stems are slender, wiry, and often reddish in color.
    • The plant can produce roots at nodes along the stems.

Identification:

  1. Prostrate Growth Habit:

    • One of the key identifying features is its low-growing, prostrate habit, forming dense mats.

  2. Distinct Ocrea:

    • The reddish-brown ocrea at the leaf base is a characteristic feature.

  3. Compact Flower Clusters:

    • The small, inconspicuous flowers arranged in compact clusters are typical of the Polygonum genus.

  4. Seed Pods:

    • After flowering, the plant produces small, triangular seed pods.

Habitat and Distribution:

  1. Habitat:

    • Common knotweed is adaptable to various habitats and is commonly found in lawns, gardens, fields, roadsides, and disturbed areas.

  2. Distribution:

    • It is a cosmopolitan species, meaning it is found in many regions around the world.

Management:

  1. Cultural Practices:

    • Regular mowing or cutting can help control common knotweed in lawns and landscaped areas.

  2. Manual Removal:

    • Hand pulling or using hand tools to remove the plants can be effective for small infestations.

  3. Herbicides:

    • Selective herbicides labeled for broadleaf weed control can be used for targeted control in lawns.

  4. Preventive Measures:

    • Creating and maintaining healthy, dense turf can help prevent the establishment of common knotweed.

  5. Seed Bank Management:

    • Since common knotweed produces a significant number of seeds, managing the seed bank through prevention of seed production is crucial for long-term control.