Wildflowers of Toronto's High Park​​

Smartweeds, Knotweeds and
Black bindweed or wild buckwheat

Family: Smartweed/Buckwheat
Genus: ​Polygonum
​​​Ocrea (leaflike tubes surrounding the stem at the nodes) assist in identifying specific speces.

Smartweed, pale or nodding
​P. lapathifolium

​Native to Ontario

Height: Usually up to 90 cm but can be 2 m

Habitat: Damp disturbed sites
Blooms: June to August

Flower: less than 2.5 mm in a dense spike, sometimes drooping, up to 10 cm.  May be pink or greenish-white.

Ocrea: hairless
Lady's thumb
​P. persicaria


​Annual (reproduced only by seeds)
Height: up to 1 m

Habitat: Roadsides and waste places
Blooms: June to September

​Flower: 2-4 mm, 5 pinkish sepals, arranged in a spike up to 4.5 cm. 

Ocrea: hairy 

The term "Lady's thumb" refers to dark blotches on the leaves.  However, this may be absent in ​P. persicaria ​and sometimes present in ​ P. lapathifolium. So this feature is not a reliable means of identification. 

Smartweed, swamp
P. coccineum

Native to Ontario

Annual (reproduces by seed and rhizomes)
Height: up to 90 cm

Habitat: Ponds and shorelines - may be aquatic or terrestrial

Blooms: July to September

​Flower: up to 4 mm in a spike up to 18 cm.
A much deeper pink than the above species.

Ocrea has no leaf-like flange.

Knotweed, prostrate
P. aviculare


Height: Up to 30 cm.  Creeps along the ground forming a mat. Can become more upright in better soil.

Habitat: Waste places, compacted soil
Blooms: June to September

​Flower: Up to 2 mm.  No petals. Sepals white and green; somtimes pinkish.

Stems are encircled by papery sheaths (ocrea) at leaf nodes. 

Knotweed, Japanese
P. cuspidatum

Introduced and invasive
Height: Up to 3 m

Habitat: Waste and disturbed areas
Blooms: June to September

​Flower: Greenish-white, 2-4 mm in 5-15 cm clusters in the upper leaf axils.

Separate male and female plants.

Spreads mainly by underground rhizomes.

Sometimes called "Mexican bamboo" due to its hollow stems.

Bindweed, black or Buckwheat, wild

Stem: Up to 2 m, prostrate and twining

Habitat: Waste places
Blooms: July to August

​Flower:  5 mm. 5 greenish-white sepals
(no petals)