scale bar = 1cm.

Pale Knotweed- a native (Persicaria lapathifolia).

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Other names: Pink Knotweed.

Family: Polygonaceae (Knotweed family). Cosmopolitan.

Native of Australia, Europe, Asia and northern Africa.

Occurrence: Grows beside streams, and the margins of swamps and lakes. It may be locally abundant.


Pale Knotweed is an annual or biennial. Occasionally the leaves and stems have dense cottony hairs.

Similar species: Slender Knotweed is similar in appearance. It does not grow as high (to about 50 cm), and the sheaths at the leaf-bases are bristly.

Photos 1, 2: Pale Knotweed on the exposed banks of Harcourt North Reservoir. 3, 4: The sheaths at the leaf bases (the ochreas) do not end in bristles.


There are three knotweeds common in the district. All grow in wet areas e.g.mud-flats, beside streams etc..
Creeping Knotweed (Persicaria prostrata). Prostrate plant. Sheaths at leaf bases develop a green leaf at the tip.
Slender Knotweed (Persicaria decipiens). Spreading or erect. Sheaths at leaf bases end in stiff hairs.
Pale Knotweed (Persicaria lapathifolia). Erect plant tp 1 metre or more. Sheaths at base of leaves summit often torn, not ending in hairs.