POLYGONACEAE (BUCKWHEAT FAMILY) 97 
PROSTRATE KNOTWEED 
Poljgonum aviculdre, L. 
Other English names: Doorweed, Knotgrass, Matgrass. 
Native. Annual or perennial. Propagates by seeds. 
Time of bloom: June to October. 
Seed-time: July to November. 
Range: Nearly everywhere in North America, Europe, and Asia. 
Habitat: Cultivated grounds, yards, roadsides, 
and waste places. 
A social, almost domesticated, weed, seeming to thrive 
best where most trampled and abused, growing in thick mats 
along hard-beaten farmyard paths, and in- 
truding persistently in lawns and garden bor- 
ders; it often fringes the stone flags of city 
sidewalks. 
Stems slender, pale green, faintly ridged, 
usually prostrate, four inches to nearly two feet 
in length, branching in all directions from 
the white, woody, rather deeply boring root. 
Smaller branches come out at many of the 
numberless “knots,” or joints, which are pale 
under the sheathing stipules. Leaves bluish 
green, nearly elliptical in shape, sessile or with 
very short petioles, a quarter-inch to an inch 
long. Flowers very small, the calyx five-parted, 
greenish white with pink margins, sitting 
solitary or in groups of two or three in the 
leaf axils; stamens usually eight, sometimes 
fewer ; style three-parted. Achenes dull brown, 
with acute apex and rounded base, three-angled, 
and. minutely ridged. This species and also the 
one following is often attacked by a white mil- 
dew. (Fig. 57.) 
Means of control 
Fic. 57.— Pros- 
trate Knotweed 
(Polygonum  avicu- 
lare). X}. 
Hoe-cutting or hand-pulling before the first seeds ripen. Dor- 
mant seeds will supply later crops to be treated in the same way 
until the ground is clean. 
H 
