VARIOUS FARM PRODUCTS 531 



time prevent washing. Mowing the roadside two or three times 

 during the summer will subdue the dog fennel and ragweed. Mow- 

 ing the stubble about two weeks after harvest in grain fields that 

 have been seeded to grass or clover will check the annual weeds and 

 at the same time produce a mulch that is very beneficial to the 

 seeding during the August drought. 



Biennials. Biennials, such as burdock, wild carrot, and bull 

 thistle, store up nourishment in thickened roots during the first 

 year of growth and during the second year they produce seed and 

 die. Many species which are ordinarily true biennials will live 

 three years, or possibly longer if seed production is prevented by 

 mowing or cutting the stem above the crown of the root. In fact 

 mowing or cutting off the main stem often induces it to branch put 

 at the base and send up several stalks in place of the one. Cutting 

 the roots below the crown usually kills them. If this work is to be 

 done by hand with a hoe, grub hoe, or spud, as is often the case 

 with bull thistles on new ground, it can be done most effectively 

 and with least labor in the fall, during the first year of growth. 

 The stools or rosettes of leaves, close to trie ground, often give little 

 suggestion of the prominent seed stalk to be grown the following 

 year; but they are sufficient to indicate to the observing eye the 

 presence of weeds. The roots at this time is more tender, and hence 

 more easily cut than in the mature plant, and one does not have to 

 strike so deep to be sure of killing it. In sod ground a spud a 

 tool like a chisel on the end of a fork handle may be used to much 

 better advantage than a hoe for cutting thickened roots below the 

 surface. 



Biennial weeds are readily killed by cultivation such as is given 

 to hoed crops, and the seeds may be cleaned out of the land by this 

 method. The weeds of this class are usually most abundant in old 

 pastures, along roadsides, and in waste places where the soil is 

 seldom disturbed. The weeds must be destroyed in these places if 

 the work of clearing the seed out of cultivated fields is to be made 

 effective. 



Perennials. Perennial weeds reproduce themselves by seeds 

 and also propagate by some form of perennial underground root 

 or stem, as the crown-forming root of dandelion and ribgrass, the 

 creeping root of Canada thistle and bindweed, the rootstock of couchi 

 grass and smartweed, the corm or solid bulb of nut grass and chufa, 

 and the bulb of wild garlic. A few plants sometimes classed as nox- 

 ious weeds have runners above ground, as Bermuda grass and 

 cinquefoil. To destroy perennial weeds seed production must be 

 prevented and the underground porti9n must be killed. Seed pro- 

 duction may be prevented by mowing when the first flower buds 

 appear, the same as in the case of annuals or biennials. In general, 

 however, the following principles apply: 



1. The roots, rootstocks, bulbs, etc., may be dug up and re- 

 moved, a remedy that can be practically applied only in small 

 areas. 



2. Salt, coal oil, or strong acid applied so as to conic in contact 



