538 FIELD AND GARDEN PRODUCTS 



has been asserted that the Canada thistle does not mature seeds in 

 some sections. Though it may not ripen seeds south of a given 

 latitude, it certainly appears to form viable seeds in unexpected 

 quarters. It springs from seed in many new places each year, and 

 spreads from the underground growth in the others. Seeds gray, 

 oblong, % inch long, striate with obscure lines and with a copious 

 pappus by which they may be carried many miles; present in hay 

 and seeds. In the latter, if known, their presence is a punishable 

 offense. The underground stems must be starved out to kill Canada 

 thistle. Destruction of this weed falls under two plans: For the 

 first, repeated cutting with hoe and applications of salt, kerosene 

 (coal oil) or sulphuric acid to the cut stems in the ground will 

 usually prove the cheapest and best method. The treatment, at least 

 the cutting, needs to be repeated as often as green leaves of the thistle 

 show above ground. Cutting alone will be sufficient to destroy them 

 but it will need to be followed for two or more seasons to be effectual. 

 In areas too large to be destroyed by hand work, the summer fallow 

 may be used, to be followed by hand treatment to kill out the small 

 remaining areas. The field should be plowed shallow in June and 

 harrowed to destroy all green tops. Upon the appearance of new 

 growth of the thistles it should be cross-plowed and again harrowed. 

 This procedure is repeated throughout the season to be followed by 

 carefull tillage the next year in corn, potatoes or some other crop 

 that is to receive all-summer hoeing and cleaning. After this some 

 patches will commonly remain to be killed out as first suggested. 

 Refuse packing or house salt, is perhaps the cheapest chemical to 

 apply after cutting. Kerosene is sometimes recommended, yet costs 

 more, while sulphuric acid is dangerous to handle, although effective 

 in burning up and destroying whatever it may be applied to. 

 Smothering with straw is rarely successful, since the thistles finally 

 grow,through it, aside from its depriving the owner of the use of 

 the land for a longer time than summer fallow. The correct prin- 

 ciple of destruction is, however, of more importance than the mere 

 method. This is to starve out the underground stems. Two or 

 more seasons will be needed. 



Common Thistle, Bull Thistle (Carduus lanceolatus) . The 

 common, purple-flowered thistle found in pastures is a biennial, 2 

 to 4 feet high, with deep tap-root. The plants start in the 

 fall and may be seen during winter . waiting for the next 

 summer to blossom and fruit. Seeds gray, larger than those of the 

 Canada thistle, *4 inch long and abundantly supplied with pappus. 

 Common in hay and seeds. Destroyed by cutting off below crown 

 before blossoming, usually not destroyed by mowing. 



Black Mustard (Brassica nigra). Black mustard is a tall, 

 prickly plant, growing in waste places and fields. It is often con- 

 fused with the next, from which it is distinguished chiefly by the 

 pods. Seeds black to dark brown, commonly spherical or ellipsoi- 

 dal, 1-20 inch long, slightly granular-roughened. Frequent in 

 seeds of clover and grasses, also in forage, but apparently less com- 

 mon than the next ; dealt with in the same manner as charlock. 



