878 



PRACTICE OF AGRICULTURE. 



Part hi. 



5539. Relative weeds, or such cultivated plants as spring up where they are not wanted, 

 give comparatively little trouble in extirpating them. The most numerous are the grasses 

 when they spring up in fields of saintfoin or lucern, or among corn crops in newly 

 broken up grass lands. The roots of chiccory, in fields that have been broken up after 

 bearing that crop for some years, of madder, liquorice, &c. are also of difficult extirpation. 

 When the potatoe crop has not been cai-efully gathered, or mustard has been allowed to 

 shed its seed, they also occasion trouble. Other similar cases will readily occur to the 

 practical man, and need not be mentioned. 



5540. Absolute weeds, or such native plants as are considered injurious to all crops, are 

 very numerous, and may be variously arranged. Some affect in a more peculiar manner 

 corn-fields and tillage lands, and these are chiefly annuals, as wild mustard, wild radish, 

 poppy, blue bottle, cockle, darnel, &c. ; or biennials, as the tliistle ; or perennials, as couch- 

 grass, knot-grass, black couch, polygonum, &c. ; on lands laid down to grass for a few 

 years, dock, ox-eye daisy, ragweed, &c. Others infest grass lands, and these are chiefly 

 perennials, such as crowfoot, one of the most diflJicult of weeds to extirpate ; thistles, 

 docks, rushes, sedges, moss, and an endless variety, of others. Some are more particu- 

 larly abundant in hedges, of which the reedy and coarse grasses, as couch-grass, brome- 

 grass, and the climbing and twining plants, as goose grass (Galium aparine), and the 

 twiners, as bindweed {Convolvulus), are the most injurious. 



5541. With^regard to the destruction of weeds, they may be classed first, according to 

 their duration. All annuals and biennials, as sand- \'IY7/, 601 

 wort (Jig. 601 b), and sorrel (c), are eflfectually 

 destroyed by cutting over the plant at any point be- 

 low that whence the seed leaves originated, as this 

 prevents them from ever springing again from the 

 roots. Perennials of the fibrous-rooted kind may 

 be destroyed in the same manner, as the crowfoot, 

 ragweed, the fibrous-rooted grasses, and many others. 

 Some fusiform rooted perennials may also be 

 destroyed by similar means ; but almost all the 

 thick rooted perennials require to be wholly eradi- 

 cated. 



5542- The perennial weeds which require their roots 

 to be wholly eradicated, may be classed according to 

 the kind of roots. The first we shall mention are 

 the stoloniferous roots or surface shoots of plants, by 

 which they propagate themselves. Of this kind is 

 the creeping crowfoot, goosefoot or wild tansey, and 

 other potentillas, mints, strawberries, black couch- 

 grass, and most of the agrostidae and other grasses. 

 The next are the under-ground creeping roots, as the 

 couch-grass, convolvulus arvensis, and other species, of bind-weed, coltsfoot (Jtg. 601 a) 

 sowthistle, several tetradynamous plants, as todflax, scrophularia, nettle, hedge-nettle, 

 (Stachys), lamium, ballota, &c. Some of these, as the bindweed and corn-mint, are ex- 

 tremely difficult to eradicate ; a single inch of stolone, if left in the ground, sending up 

 a shoot and becoming a plant. The creeping and descending vivacious roots are the 

 most difficult of all to eradicate. Of this class are the polygonum amphibium, (fig. 

 602 a), the reed {Arundo p)hragmites), the horse-tail {Equisetum,fig. 602 b), and some 

 others. These plants abound in deep clays, which have been deposited by water, as in 

 the carses and clay-vales of Scotland. In the carse of Falkirk for example, the roots of 

 the polygonum amphibium are found every where in the subsoil alive and vigorous. 

 They send up a few leaves every year in the furrows and on the sides of drains, and when 

 any field is neglected or left a year or two in grass, they are found all over its surface. 

 Were this tract to be left to nature for a few years, it would soon be as completely co- 

 vered with the polygonum as it must have been at a former age, when it was one entire 

 marsh partially covered by the Firth of Forth. The horse-tail is equally abundant in 

 many soils, even of a drier description ; and the corn thistle, (Serratula arvensis,Jig.60l e) 

 even in dry rocky grounds. Lightfoot {Flora Scotica) mentions plants of this species 

 <iug out of a quarry, the roots of which were nineteen feet in length. It would be useless 

 to attempt eradicating the roots of such plants. Tfie only means of keeping them 

 under, is to cut off their tops or shoots as soon as they appear ; for which purpose, 

 lands subject to them are best kept in tillage. In grass lands, though they may 

 be kept from rising high, yet they will, after being repeatedly mown, form a stool or stock 

 of leaves on the surface, which will suffice to strengthen their roots, and greatly to injure 

 the useful herbage plants and grasses. 



