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Common Knotgrass

©Philip Precey

Common knotgrass

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Scientific name: Polygonum aviculare
Despite its name, Common knotgrass is not a grass, but is actually related to the docks. It has wiry stems that grow along the ground, and is a weed of waste ground, gardens and arable fields.

Top facts

Stats

Height: up to 60cm

Conservation status

Common.

When to see

May to October

About

Common knotgrass is found along the seashore, on waste ground, fields and roadside verges, and in gardens. This widespread plant has tiny, pale pink flowers that are very easy to miss as they appear so close to the stem; it blooms from May to October. Common knotgrass is also known as 'Iron-grass' because of its tough, wiry roots that make it especially hard to pull up from the ground.

What to look for

Common knotgrass has oval, leathery leaves of varying sizes, and tiny pink flowers that arise where the leaves join the wiry stems. It often grows horizontally along the ground.

Where to find

Found throughout the UK, but less common in North East England and North East Scotland.

Habitats

Did you know?

Common knotgrass can be used to make dyes of indigo, yellow and green.