Polygonaceae . . . . Knotweed family

Choose the best approximation from 3 groups:     Docks,     Knotweeds,    or    Peppers

Docks,
Knotweeds,
Peppers

Docks and similar:

Oxyria
Dock
Rhubarb
Sorrels
Also consider the following similar-looking plants:
Amaranthaceae

Knotweeds and similar:

Polygonum
Fallopia
Fallopia
Fagopyrum

Reynoutria
Muehlenbeckia

Persicaria, peppers and bistorts:

Koenigia polystachya
Koenigia campanulata
Persicaria capitata
Bistorta amplexicaulis
Himalayan Knotweed
Lesser Knotweed
Pink-headed Persicary
Red Bistort

Persicaria maculosa
Persicaria amphibia
Persicaria amphibia
Bistorta officinalis
Redshank
Amphibious Bistort
Amphibious Bistort
Bistort

Persicaria hydropiper
Persicaria lapathifolia
Bistorta vivipara
Water pepper
Pale persicary
Alpine Bistort

Bistorta (was Persicaria) . . . . . Bistorts

Bistorta amplexicaulis (was P. amplexicaule) . . . . Red Bistort

Widely grown in gardens and cn escape

Bistorta officinalis (was P. bistorta) . . . . Bistort

Throughout BI

Bistorta vivipara (was P. vivipara) . . . . Alpine bistort

Restricted to mountains, esp. in N En and Sc
A couple of other garden escapes can occur: Rockery bistort (B. affinis) and Red bistort (B. amplexicaule)

Fagopyrum . . . . . Buckwheat

Fagopyrum esculentum . . . . . Buckwheat

Largely a relic of farmland cultivation

Fallopia . . . . . Knotweeds

Fallopia baldschuanica . . . . . Russian vine

Fallopia convolvulus . . . . . Black bindweed

A common weed of waste and arable land

Similar is Copse bindweed (Fallopia dumetorum), to 2 m, rare in S En

Fallopia japonica . . . . . Japanese knotweed

See Reynoutria

Koenigia . . . . . Knotweeds

Several spp. recently transferred here from Persicaria

Koenigia campanulata (was Persicaria campanulata . . . . Lesser knotweed

Naturalised garden escape in various parts of BI; petals divided c.1/2 way to base

Koenigia polystachya (was Persicaria wallichii) . . . . Himalayan knotweed

Scattered throughout BI; to 1.5 m; petals divided nearly to base

Several other spp. occur as garden escapes, including Chinese knotweed (K. weyrichii

Koenigia islandica . . . . Iceland-purslane

A rare tiny annual of Skye and Mull

Muehlenbeckia . . . . . Wire plant

Muehlenbeckia complexa . . . . . Wire plant

Uncommon garden escape

Oxyria . . . . . Mountain sorrel

Oxyria digyna . . . . . Mountain sorrel

Local on mountains

Persicaria . . . . Knotweeds, peppers, bistorts

Persicaria amphibia . . . . Amphibious bistort

Throughout BI, occurs in both aquatic and terrestrial forms

Terrestrial form similar to P. maculata but without lf spots

Persicaria bistorta . . . . Bistort

See Bistorta officinalis

Persicaria campanulata . . . . Lesser knotweed

See Koenigia

Persicaria capitata . . . . Pink-headed persicaria

Naturalised in S and CI

Persicaria hydropiper . . . . Water pepper

Very sharp peppery taste; wet places over BI

Persicaria lapathifolia . . . . Pale persicaria

Dense heads of greenish flowers; lvs sometimes with dark spot; Throughout BI

Persicaria maculosa . . . . Redshank

Leaves usually with large dark spot; throughout BI

Persicaria vivipara . . . . Alpine bistort

See Bistorta vivipara

Persicaria wallichii . . . . Himalayan knotweed

See Koenigia

Polygonum . . . . . Knotgrasses

Difficult to separate the various spp. recognised: P. aviculare has leaves crowded together, and of markedly different sizes, P. depressum has equal-sized lvs, while P. arenarium has topmost fls longer than subtending bracts. Three examples shown

Polygonum arenarium . . . . Lesser Red-knotgrass

Polygonum aviculare . . . . Knotgrass

Common throughout BI; lvs crowded together, petioles not extending from sheath

Polygonum boreale . . . . Northern Knotgrass

Mainly nr. coast of Sc; petiole extends beyond stipules (arrow)

Polygonum depressum (usually recorded as P. arenastrum) . . . . Equal-leaved Knotgrass

The commonest sp. in BI; lvs on main and side stems same size
Other spp. include: Polygonum rurivagum (Cornfield Knotgrass) and the rare Polygonum maritimum (Sea Knotgrass)

Reynoutria (from Fallopia) . . . . Knotweeds

Reynoutria japonica (was Fallopia japonica) . . . . . Japanese knotweed

A very pernicious escape well established in many areas and hard to eradicate; lvs <15 cm long, can grow to 2-3 m

Less common but even larger (to 4-5 m, with lvs >20 cm long, cordate) is Giant knotweed (R. sachalinensis), widespread

Rheum . . . . . Rhubarbs

Rheum x rhabarbarum. . . . Rhubarb

Rheum palmatum. . . . Ornamental Rhubarb


See also:   
Monk's rhubarb

Rumex . . . . . Docks

True docks: Rumex (select from fruit appearance) - or scroll through spp. below

Rumex acetosa . . . . . Common sorrel

Rumex acetosella . . . . . Sheep's sorrel

A generally rather small plant - often <10-15 cm tall; much smaller than R. acetosa; leaves vary from narrow arrow-shaped to broad

Rumex alpinus . . . . Monk's rhubarb

Scattered in Sc and N En

See also:   
Rhubarb

Rumex conglomeratus . . . . . Clustered dock

Damp places; all 3 of 3 tubercles developed (c.f. R. sanguineus)

Rumex crispus . . . . . Curled dock

Leaves with characteristic wavy/crinkled edges

Rumex hydrolapathum . . . . . Water dock

A large plant to >2m; Scattered by ponds and streams

Rumex longifolius . . . . . Northern dock

Damp ground often by water - Sc and N En

Rumex obtusifolius . . . . . Broad-leaved dock

Abundant

Rumex pulcher . . . . . Fiddle dock

Usually with violin-shaped leaves

Rumex rupestris. . . .Shore dock

Very local by the sea between CI and Anglesea

Rumex sanguineus . . . . . Wood dock

Mostly in woods or hedgerows; only 1 of 3 tubercles developed (c.f. R. conglomeratus)
Several other, mostly rare or local, spp. and hybrids can occur