Bistorts, Knotgrasses & Allies
Dock Family - Polygonaceae
Common Water-pepper Persicaria hydropiperNative. throughout Europe, Asia and much of Australia; widely introduced elsewhere. Typically in damp, muddy places. A slender species with open, gracefully arching flower spikes; leaves have a strong, peppery bite to them and usually clearly undulate margins.
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Redshank Persicaria maculosa
Native throughout Eurasia and widely introduced elsewhere as a weed of cultivation. A remarkably variable species that may be anything from 20-100cm in height. Leaves typically with a dark blotch in the middle (though not always) and flowers pink or cream. Best told from similar species by the lack of yellowish glands at the base of the flower spike.
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Pale Persicaria Persicaria lapathifolia
Considered native throughout the Northern Hemisphere and southward into central Africa and parts of Australia. A very variable species that may be anything from 20-100cm in height and often well branched to form shrubby growths. Leaves typically without a dark blotch in the middle (though not always) and flowers pink or cream. Best told from Redshank by the yellowish glands at the base of the flower spike which have the glandular heads larger than their stalks. Seeds are flattened and disc-shaped. In really difficult individuals it is worth checking the tips of the veins on the tepals, which in Pale Persicaria branch to frorm distinctive, anchor-shaped marks.
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Amphibious Bistort Persicaria amphibia
Native throughout the Northern Hemisphere in wet and seasonally wet ground and ponds. A perennial species that can form extensive patches of vegetation. This species produces rather narrow leaves when growing on land, but also grows in water and then produces wider leaves that float at the surface. Leaves told from other species by the rounded, heart-shaped bases and by the stiff white hairs that often arrange themselves in lines on the leaf. Flowers deep pink.
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Horsetail Knotgrass Polygonum equisetiforme
Native to the Mediterranean region and western Central Asia. A distinctive species that forms twiggy stands of bare stems, somewhat resembling a broom bush or horsetail.
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Sea Knotgrass Polygonum maritimum
Native to the Mediterranean region and northwards along Atlantic coast of Europe. A plant of sandy beaches.
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Common Knotgrass Polygonum aviculare
Native throughout most of the Northern Hemisphere and widely introdcued elsewhere. Sprawling or trailing annuals with narrow leaves and long, wiry stems. The leaves of the main stems are clearly larger than those of the side stems (though take care when assessing this as the leaves of the main stems tend to drop as the plant continues to grow). Tepals white with a green central stripe, sometimes tinged pale pink. Nutlets pointed, 2.5-3.5mm long, concave on all three sides.
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Equal-leaved Knotgrass Polygonum arenastrum
Polygonum depressum Native throughout Europe and the Mediterranean Region, eastwards into Siberia and through the Middle East to Pakistan. Sprawling or trailing annuals with ovate leaves and wiry stems; typically less elongate, more compact than Common Knotgrass. The leaves of the main stems are about the same size as those of the side stems. Tepals white with a green central stripe, sometimes tinged pale pink. Nutlets pointed, 1.5-2.5mm long, concave on only one side, convex on the other two sides.
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Black Bindweed Fallopia convolvulus
Native throughout Eurasia and the Mediterranean Region; widely introduced elsewhere. A trailing or twining plant, scrambling over other vegetation. The spear-shaped leaves may be confused with those of the true bindweeds, but the flowers are very different and there is a small ocrea present at the leaf base.
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