Douglas knotweed, an annual herb with narrow, alternate leaves and erect 

 stems sheathed at the jointed nodes, is widely distributed, ranging from British 

 Columbia and California eastward to Texas, Nebraska, New York, Maine, and 

 Ontario. However, east of the Rocky Mountains it has probably been natural- 

 ized, since its distribution is local. Douglas knotweed was named in honor of 

 David Douglas (1799-1834), a distinguished Scotch botanical explorer. 



Douglas knotweed abounds on rocky, sandy, or impoverished soils, especially 

 in waste ground and on sites where trampling, excessive grazing, or other 

 destructive influences have largely destroyed the natural, perennial vegetation. 

 Sampson * considers this species one of the key plants of the ruderal-early-weed 

 stage, characterized by annuals qualified for the invasion and occupation of 

 lands where the soil has been seriously impaired. These low-value annuals, 

 mostly weeds, with shallow root systems and strong seed habits, are, however, 

 efficient eventually in accumulating sufficient organic matter to support more 

 desirable perennial plants. 



This herb is practically worthless as forage for cattle and horses and is only 

 fair feed for sheep, except on severely overgrazed areas, where it dominantly 

 abounds and is moderately cropped by both sheep and cattle. Under such 

 conditions it furnishes an amount of feed equal to that of all the other annual 

 weeds combined. 1 It is of little forage importance on ranges in good condition. 



KNOTWEEDS (Poly'gonum spp.) 



Knotweeds, also known as doorweeds and knotgrasses, compose a fairly 

 large and widely distributed genus, with some 36 species in the West. The 

 genus belongs to the buckwheat family (Polygonaceae) ; it includes both annual 

 and perennial plants, a number of the western species being woody at the base 

 (undershrubs). In this discussion the genus Polygonum is considered in its 

 more restricted sense, exclusive of the following genera: Fleeceflower (Acono'- 

 ffonum), cornbind (Bilderdry'kia, syn. Tinia'ria), bistort (Bistor'ta), tovara 

 (Tovcwa), and tearthumb (Tracaulon), which are regarded by some authors 

 as too closely related to Polygonum to rate generic rank. The generic name 

 Polygonum is from the Greek polus, many, and yonu, knee, referring to the 

 swollen stem joints characteristic of many species. This knotted appearance of 

 the stem is also emphasized in the common name. 



This representative group of the buckwheat family is widely distributed 

 throughout the West and occurs in diverse habitats, ranging from extremely 

 dry to very wet or marshy sites. Usually, these plants abound on poor soils, 

 or on areas where such disturbing influences as overgrazing and trampling 

 have depleted the perennial plant cover. On the range they generally grow 

 in greatest abundance in the vicinity of depleted bedgrounds, saltgrounds, and 

 other severely abused sites. Some species are common weeds in cultivated 

 ground; others appear along roadsides. Although generally ranking as un- 

 desirable species, knotweeds often mantle denuded areas with a fairly dense 

 cover, which provides some soil protection. 



These species, are usually low in palatability, being practically worthless as 

 forage for cattle and horses, and only fair for sheep and goats; occasionally, 

 however, they furnish an appreciable amount of sheep forage. Inferior forage 

 quality explains why they are cropped somewhat lightly even on heavily grazed 

 ranges, but as they produce an abundance of seed these plants tend to increase 

 and replace their betters which have succumbed to excessive grazing. Hence, 

 a superfluity of knotweed on a range generally indicates destructive depletion 

 from very severe overgrazing. 



In the main, knotweeds are hairless, much-branched, erect, or sprawling 

 herbs, with alternate and somewhat fleshy or leathery, stalkless leaves, jointed 

 to the stipules (ocreae), which sheath the stems at the nodes. The small 

 flowers are borne in clusters in the leaf axils, sometimes bunched near the 

 branch ends in spikes, racemes, or heads. The flowers lack petals; the outer 

 flower parts (calyx) consist of four to six (usually five) nearly separate, petal- 

 like sepals, which are pink, rose, or white, or often greenish and with pale 

 or brightly colored margins. The small, seedlike fruits (achenes) are three- 

 angled, brown or black, and surrounded by the persistent calyx. 



1 Sampson A. W PLANT SUCCESSION IN RELATION TO RANGE MANAGEMENT. U. S. Dept. 

 Agr. Bull. 791, 76 pp., illus. 1919. 



