WEEDS AND MOSS. 83 



they are partly grown and have done some damage. Fre- 

 quent light stirrings of the soil with cultivator, harrow, or 

 rake are the cheapest mode of weed destruction. Rotation 

 of crops and continuous cropping of the land are amongst 

 the best preventives and exterminators of weeds. The 

 better the system of husbandry the fewer the weeds. 



In the struggle with weeds it is well to consider the 

 longevity of the various species. Annual weeds, those 

 which naturally die after the season's growth, require no 

 special treatment. Biennial species, those which die at the 

 end of the second year, may be held in check by preventing 

 them from seeding, as by mowing them when coming into 

 flower. Examples of this class are the mullein, wild carrot, 

 and field or bull thistle. Perennial species, those which 

 live indefinitely, often require particular treatment. Some 

 of the worst perennial species are Canada thistle, white or 

 ox-eye daisy, toad-flax, live-forever, docks, and various 

 grasses. Very frequent, persistent, and thorough cultiva- 

 tion will destroy any of these. Cultivation should be 

 repeated even before the weeds recover sufficiently to take 

 root again. Seeding down and mowing the weeds with the 

 hay will destroy most weeds. In dry and sandy soils three 

 or four thorough plowings during the season will destroy 

 Canada thistles and other pests, particularly in dry years, 

 but on richer and retentive soils greater thoroughness must 

 be practised. 



Weeds in lawns. — Weeds usually come up thickly in 

 newly sown lawns. They are to be prevented by the use of 

 commercial fertilizers or very clean manure and clean grass- 

 seed. Clean June-grass, or blue-grass, seed is usually best. 

 Grass-seed should be sown very thickly — 3 to 4 bushels 

 to the acre — and annual weeds cannot persist long. Fre- 

 quent mowings during summer will keep these weeds down, 

 and most species will not survive the winter. In old lawns 

 most perennial weeds can be kept down by frequent mow- 

 ings, with a good lawn-mower. Grass can stand more 

 cutting than weeds. If mowing cannot be practised often 



