BULLETIN 128. TORONTO, AUGUST, 1903. 



Ontario Agricultural College and Experimental Farm. 



SOME COMMON ONTARIO WEEDS. 



BY t> 



i 



F. C. Harrison, Professor of Bacteriology, and William Lochhead, Professor 



of Biology. 



A leading educational authority lately said he did not believe 

 that one farmer in a dozen could give the generally accepted common 

 names of twenty of our common weeds. Whether this be so or not, 

 one thing is certain, viz., that noxious weeds are spreading very 

 rapidly in the Province of Ontario, and farmers need all the informa- 

 tion they can get in preventing further loss from this very serious 

 hindrance to successful agriculture. Hence the preparation of this 

 bulletin for the Committee on Economic Botany appointed by the Ex- 

 perimental Union in connection with the Ontario Agricultural College. 



The writer wishes to express his thanks lor the assistance rend- 

 ered by Wm. McCallum, B.S.A., who has labored unremittingly in 

 collecting plants and in arranging material ; and to Norman Ross, 

 B.S.A., for his exact and artistic pen-drawings of the plants found in 

 the bulletin. Mr. Ross made the drawings from specimens collected 

 in this vicinity and from photographs taken in the laboratory. 



Why Weeds are Injurious. 



A weed has been defined as any plant out of place ; and, in that 

 sense, a wheat plant in a field of turnips is a weed. _ 



Most weeds do considerable,and some very much.injury to the crops 

 in which they are found. They produce these effects in several ways : 



1. They absorb soil moisture. The amount of water w-hich is 

 taken up by weeds and evaporated from the surface of the leaves is 

 very great. For instance, an average Mustard plant pumps from the 

 soil about fourteen ounces, or seven-tenths of a pint, per day ; a sun- 

 flower, thirty-three ounces ; and so on. The transpiration is generally 

 in proportion to the surface of the leaf ; but thin leaves transpire, or 

 throw off water, more freely than fieshy ones. Consequently Aveeds 

 having large leaf-surface draw from the soil and give oflf through the 

 leaves a large amount of water, and thereby rob the surrounding 

 plants. Many botanists consider this waste of moisture the most seri- 

 ous injury done by weeds. 



2. They use plant food. Weeds naturally make use of the same 

 food as the cultivated plants among which they grow. Consequently 

 they deprive a crop of a large amount of the available nourishment ; and 



