98 PROTECTION OF PLANTS, 1915-16 



start a great many weed seeds germinating; these may be harrowed down 

 or wnll be killed by frost. 



The biennial and annual weeds are controlled in practically similar 

 ways. A biennial stores up strength, the first year, and flowers the next. 

 Often no stems show the first season, as in burdock, wild carrot, blue-bur, 

 and wild parsnip, and only a rosette or circle of leaves at the ground shows. 

 Cut biennials off below the bud in the fall of their first year, or keep mown. 

 These sometimes, however, live on for three or more years, if not allowed 

 to flower. In general, the control means as regards seeds and seedlings 

 is just that for annuals. 



Perennial Weeds 



More menacing to the grain grower and stock farmer in particular 

 are the perennial weeds. Spreading by seeds and by root stocks, roots, 

 or trailing stems, they live on from year to year, spread rapidly, and resist 

 any but the most persistent and well-planned treatment. Included here are 

 the field sow-thistle, Canada thistle, the paintbrush, field bindweed or con- 

 volvulus, the dandelion and the plantains. In the West, sow-thistle has called 

 forth special efforts of government and farmers to fight it. Grain fields 

 have to be fallowed for one or two seasons, and steady cultivation kept up. 

 The great point is to prevent the entrance of the weed by seed or roots 

 carried by implements or waggons. The appearance of perennial weeds 

 should be regarded as a challenge, to be at once accepted. At all events 

 perennials must not be allowed to go to seed. If this is done the roots will 

 spread slowly, and may be starved out by cultivating and cutting off all 

 green growth. 



Perennials in pastures, such as paintbrush and dandelion, may be 

 kept down and killed by sheep. Thistles will only be eaten, however, if 

 food is scarce. A success has been made of the use of pigs for rooting up 

 bindweed (convolvulus), where the pigs were in a confined space, but this 

 weed "can be eradicated by clean cultivation if thorough and persistent. 

 (9). The case requires going over the land once every week or ten days." 

 In California "orchardists use the weed knife, which runs under the surface 

 of the soil at a depth of from 3 to 6 inches." (9). The knives are attached 

 to a rig like the two-horse corn cultivator, or the knives may be carried on 

 a drag beam 8 to 12 feet wide. The knives are all inclined inward. It is 

 hard to use in cloddy soil, however. Following cultivation, smother crops 

 may be planted; particularly are "alfalfa, buckwheat, soy-beans and millet" 

 commonly used (11). The Ontario Agricultural and Experimental Union 



