Polygonum FNA Key - Sask

The following key was created as follows:

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Started with key to Polygonum species in the Flora of North America (FNA)

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Removed all species not found in Saskatchewan.  List of Saskatchewan species obtained from Checklist of the Vascular Plants of Saskatchewan by Vernon L. Harms.

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Added rarity/abundance information, also taken from Harms. CC - very common, C - common, FC - fairly common, UC - uncommon, VUL - vulnerable, THR - threatened, END  - endangered, ADV? - possibly adventive, R - rare (applies to introduced species only).

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Added common names.

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Linked species name to species description in Flora of North America

    Stems distinctly and regularly 8-16-ribbed; leaf blade venation pinnate, secondary veins conspicuous; anthers whitish yellow; nearly worldwide.  Polygonum section Polygonum
   
Stems 4-gonous, ribs obscure or absent; leaf blade venation parallel, secondary veins not conspicuous; anthers pink to purple; mostly w North America.  Polygonum section Duravia

Polygonum section Polygonum

1.  Leaves in distal part of inflorescence reduced, not overtopping flowers (shorter than or equaling flowers); inflorescences axillary and terminal, spikelike.  Polygonum ramosissimum (Bushy Knotweed) C
      Leaves in distal part of inflorescence overtopping flowers; inflorescences entirely axillary.  (2)

2.  Achenes striate-tubercled, uniformly tubercled, or obscurely tubercled.  (3)
     Achenes smooth to roughened (8)

3.  Plants green to bluish green; margins of tepals white, pink, or red.  (4)
     Plants light green or yellowish; margins of tepals green to yellow  (6)

4.  Achenes coarsely striate-tubercled.  Polygonum aviculare (Doorweed) C
     Achenes obscurely tubercled.  (5)

5.  Plants dark brown to black after drying; distal part of ocreae disintegrating into persistent fibers, brown.  Polygonum ramosissimum (Bushy Knotweed) C
      Plants green after drying (sometimes whitish from powdery mildew); distal part of ocreae persistent, silvery.  Polygonum aviculare (Doorweed) C

6.  Perianth tube 40-55% of perianth length; tepals keeled; pedicels 1.3-1.8(-2) mm, enclosed in ocreae.  Polygonum achoreum (Striate Knotweed) C
      Perianth tube 20-38% of perianth length; tepals not keeled; pedicels 2-7 mm, exserted from ocreae. (7)

7. Leaf blades elliptic to obovate; distal parts of ocreae persistent, silvery; achenes striate-tubercled.  Polygonum erectum (Erect Knotweed) Listed for SK in FNA but reported non-verified by Harms.
     
Leaf blades narrowly elliptic to lanceolate, rarely ovate; distal parts of ocreae soon disintegrating into persistent brown fibers; achenes uniformly tubercled.  Polygonum ramosissimum (Bushy Knotweed) C

8. Perianth tube 40-57% of perianth length.  Polygonum aviculare (Doorweed) C
    Perianth tube 18-38% of perianth length.  Polygonum ramosissimum (Bushy Knotweed) C

 

Polygonum section Duravia

1.  Apices of tepals acute to acuminate; achenes light yellow, light brown, or greenish to dark brown, smooth or with longitudinal ridges.  Polygonum polygaloides (Dense Knotweed) THR
    
Apices of tepals rounded; achenes black, smooth or minutely tubercled.  (2)

2.  Pedicels reflexed.  Polygonum douglasii (Douglas Knotweed) UC/FC?
     Pedicels erect or erect to spreading.  (3)

3.  Inflorescences dense, cymes overlapping at branch tips.  Polygonum spergulariiforme (Spurry Knotweed) END
    
Inflorescences elongate, cymes widely spaced along branches.  Polygonum sawatchense (Sawatch Knotweed)  Listed for SK in FNA only.