Polygonum arenastrum Bor.   =Polygonum aviculare   Polygonaceae (Buckwheat Family)   Eurasia   Common Knotweed

                                      September Photo

Plant Characteristics:  Annual with prostrate or ascending bluish-green slender, terete stems, not sharply angled, 1-12 dm. long; lvs. lanceolate  to almost oblong, 5-20 mm. long, blue-green, scattered to approximate, not much reduced upward, joined with the ocreae and 1-nerved, mostly 2 or more in the axils, short pedicelled; branch-lvs. much smaller than stem lvs.; stipule-sheaths silvery, soon torn; fls. 1-5 in axillary clusters; calyx 2-3 mm. long, greenish with pinkish to purplish margins, persistent, divided almost to base; stamens 8, rarely 5; aks. dull or slightly shiny, 2-2.5 mm. long, somewhat roughened.

Habitat:  Common weed in dooryards, waste places, etc.  May-Nov.  Variable.

Name:  Greek, poly, many, and gonu, knee or joint, because of the thickened joints on the stem.  (Munz, Flora So. Calif. 701).  Latin, avis, avicul, bird and arius, suffix added to noun stems to form adjectives denoting belonging to.  (Jaeger 26,32). Latin, arena, sand, a sandy place. (Jaeger 25).  Arenastrum may refer to a soil type in which the plant is found?

General:  Occasional in the study area.  Photographed on the North Star Flats.  (my comments).      A decoction of the plant mixed with oak bark is used as a substitute for quinine.  (Coon 235).      Whole large sections of many lawns are composed not of grass but of knotgrass, which indicates hard soil, lazy lawn keepers, and careless walkers.  The slender pale green stems are usually prostrate and measure four inches to two feet in length.  Branches emerge from the joints (or "knots"), which appear paler within the sheath this common to the genus Polygonum.  Though in 1809 William Pitt included knotgrass in his list of the worst weeds of arable land, it has been found to have a number of uses.  Its juice stops nosebleed and a tea brewed from it has been used to stop diarrhea and hemorrhages.  The American Indians had the patience to collect its tiny seeds and include them with other seeds in a pinole.  In Shakespeare's day some thought this plant could inhibit the growth of children; thus his "hindering knotgrass," in "A Midsummer Night's Dream."  (Crockett 175).       Used as an astringent and diuretic.  (Meyer 34).       P. aviculare is combined with P. arenastrum in the 1993 Jepson manual.  (my comment).  P. aviculare is very closely related to P. arenastrum, apparently misapplied in California.  (Hickman, Ed. 1349).

Text Ref:  Hickman, Ed. 888, 1349; Munz, Calif. Flora 362; Munz, Flora So. Calif. 703; Robbins et al. 134.

Photo Ref:  June 83 # 7A,8A; Sept 1 83 # 9.

Identity: by R. De Ruff, confirmed by F. Roberts.

First Found:  June 1983.

Computer Ref:  Plant Data 257.

Have plant specimen.

Last edit 5/20/05.

                                 June Photo                                                                                     June Photo