PLATE 23. 



GREAT RAGWEED. Ambrosia trifida, L. 



Uther English names : Tall Kagweed, Crownweed, Kmgweed, Bitter- 

 weed. 



(Noxious: Doin., Ont., Man., X.W.). 



Native. Annual. A tall, coarse branching plant, 4 to 8 feet high, with 

 very rough stems and leaves; pale green and bearing the sterile and fertile 

 flowers in different heads on the same plant, the sterile in long, slender spikes 

 at the ends of the branches, and the fertile two or three together, sessile in 

 the nxils of the leaves at the base of the spikes, v'^terile flowers cup-shaped, 

 nodding, \ inch across ; anthers yellow and conspicuous ; fertile flowers in- 

 conspicuous; pistils slender and purplish. Leaves opposite on long margined 

 petioles, very variable in shape, on young plants deeply indented but scarcely 

 lol>ed; as the stems grow, 3 or even 5-lobed leaves are produced, and on many 

 plants may be found leaves without lobes. Seeds (achenes) [Plate 55, fig. 57 

 — natural size and enlarged 4 times] brown, urn-shaped, about \ inch long, 

 tipped with a tapering beak and bearing around the base of this about one- 

 third from the top, like the points of a crown, G or 8 blunt spines which are 

 the ends of more or less distinct ribs ; this crown-like appearance of the top 

 of the seed has suggested the names Kingweed and Crownweed, sometimes 

 used by millers. 



Tivie of Flowering : July; seed ripe August. 



Propagation : By seed, in grain and carried by water. 



Occurrence: Ontario and occasional in other eastern provinces. Abun- 

 dant in the rich Red River valley lands in Manitoba. Not extending west 

 as a weed, but sometimes seen along the railways. 



Injury: This coarse annual, when in crops, crowds and starves grain 

 growing near it, but the chief loss to farmers is due to the difficulty experi- 

 enced by millers in separating the seeds from grain, owing to its similarity 

 in size and weisrht to wheat; the spines also are said to catch in the meshes of 

 the screens and to give much trouble in the cleaning process. 



Remedy : This is one of the few weeds in Manitoba for which hand pull- 

 ing is a practical remedy. As a rule, the plants are conspicuous and grow 

 near the edges of fields. A little labour in pulling before the seeds are ripe, 

 being well repaid by the clean crop reaped, special attention should be given 

 to fields liable to be flooded. Good work may frequently be done for this as 

 for several other weeds by running a mowing machine around the edges of 

 fields Ix-fore the seeds are ripe. 



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