KNOTGRASS

Polygonum aviculare

Dock & Knotweed Family [Polygonaceae]

month8jun month8june month8jul month8july month8aug month8sep month8sept month8oct month8nov

status
statusZnative
flower
flower8white
flower
flower8red
inner
inner8pink
morph
morph8actino
petals
petalsZ5
stem
stem8round

2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Almost ubiquitous throughout the UK apart from parts of North Scotland and other highland areas, but quickly disappearing by the decade in Eire and parts of middle England.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Un-like most other Knotgrasses, Leaves on main stem about two or three times longer than those on branches.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Here growing in coastal sand washed frequently by the tides.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Tiny flowers in small bunches at regular intervals along the stems.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Flowers emerge from silvery papery sheaths, which later turn brown.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Between 3-6 flowers in a bunch together.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Flower 'petals' (actually tepals) are reddish-pink, pink or white and five in number.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Silvery sheaths a bit like tracing paper, semi-transparent.


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
fruit is more or less hidden by flower (unlike those on Ray's Knotgrass, Cornfield Knotgrass and the much rarer Sea Knotgrass which are big enough to emerge from the top).


Not to be semantically confused with : Knotweeds such as Japanese Knotweed (Fallopia japonica) [a plant with similar name].

The Genus name of Knotgrasses, Polygonum can easily be misinterpreted as Polygonatum which is the genus name of Solomon's-seals such as Angular Solomon's-Seal (Polygonatum odoratum). Easily mis-identified as : other Knotgrasses :

  • Equal-leaved Knotgrass (Polygonum arenastrum) which has equal-sized leaves.
  • Ray's Knotgrass (Polygonum oxyspermum) which grows only on the coast and has larger flowers, a sturdier stem, is less sprawling, and the fruits visibly emerge from the dead flowers.
  • Sea Knotgrass (Polygonum maritimum) very rare occurring only in very few places on the southern coast of the UK. Larger, more-open flowers and stouter even that Ray's Knotgrass.
  • Northern Knotgrass (Polygonum boreale) but that now occurs only in the North of Scotland and is very rare at that. Leaves in two differing sizes, the larger size wider than any other Knotgrass. Flowers emerge well clear of the silvery sheaths.
  • Cornfield Knotgrass (Polygonum rurivagum) which mainly occurs scattered around the southern half of the UK and grows only in limy arable fields.

Some similarities to : Water Peppers such as Water Pepper (Persicaria hydropiper), Small Water-pepper (Persicaria minor) and Tasteless Water-pepper (Persicaria mitis) which also have 5-petalled flowers in small groups appearing in whitish papery sheaths but these are usually upright rather than sprawling.

No relation to : Knotted Crane's-bill, Knotted Hedge-parsley, Knotted Pearlwort or Knotted Clover which all belong to differing families. [plants with similar names belonging to differing families].

Knotgrass is the commonest knotgrass and like Ray's Knotgrass (Polygonum oxyspermum) and Sea Knotgrass (Polygonum maritimum) it grows near the shore and on gull colonies but also, un-like those, on bare ground or cultivated fields as far from the sea as you can possibly get.


  Polygonum aviculare  ⇐ Global Aspect ⇒ Polygonaceae  

Distribution
 family8Dock & Knotweed family8Polygonaceae

 BSBI maps
genus8Polygonum
Polygonum
(Knotgrasses)

KNOTGRASS

Polygonum aviculare

Dock & Knotweed Family [Polygonaceae]