THE MUSTARD FAMILY 99 



where this weed gives trouble should receive clean cultivation 

 until late in the fall. Where Tansy Mustard is troublesome 

 in winter wheat, harrowing in early spring will tear out the 

 rosettes without injuring the wheat. Waste places where it 

 thrives should be sown to permanent grass and the weed growth 

 kept cut until the grass has possession of the soil. Frequent 

 cutting will prevent it from seeding along roadways and the 

 borders of fields. 



ALLIED SPECIES: Gray or Crowded Tansy Mustard 

 (Sisymbrium incisum Engelm., var. Hartwegianum (Fourn.) Watson) 

 is also a tall, coarse biennial, with much divided foliage like the 

 above, but differs by being covered with short, gray, downy hairs 

 and in its more erect habit of growth. It has pods only 1/4 inch 

 long, all crowded close to the slender branches which form a nar- 

 row spike-like raceme. Gray Tansy Mustard is the commoner 

 and more widely distributed plant of the two. It flowers and 

 ripens its seed some weeks later. 



The seed (Plate 74, fig. 41) resembles that of Green 

 Tansy Mustard in shape and colour but is smaller, a little more 

 flattened by compression in the pods and more abruptly cut off 

 transversely. 



These two coarse biennials grow only from seed, but they 

 throw out long branches from their white tap roots and draw 

 nourishment from a wide area. As they stand considerably 

 above the crop, they are a conspicuous advertisement of negli- 

 gent farming. 



Now is the time, before the thistle blow, 

 While gule is in the flower, and charlock breathes 

 Its cloying scent around, the weeding task 

 To urge between the turnip's verdant ranks. 

 Emburied by the double mould-board, down 

 On either side the noxious race are laid. 

 While, by the waves of crumbling earth heaved up, 

 The plants are cherished. 



James Grahame, British Georgics, 1812 



