This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
A weed is a plant that is growing where it is desired that something else shall grow. It follows that a plant may be a weed in some places and not in others. Cockle in the wheat fields is most undesirable; New England Asters and Black-eyed Susans are detrimental when growing in the meadow; but all are graceful and beautiful plants, and, growing in a protected flower garden, would be a feast to color-loving eyes. It is well that most pernicious plants have little beauty to make them desired in the posy beds of the farm home, for, though it is necessary to label some bad weeds as "escapes from cultivation," they are not numerous nor among the most evil of their kind.
Each weed has its own way of winning in its struggle with the farmer's crops and its habits must be learned in order to know how to get the better of it. This can be done only by a study of the life history of the species. According to their nature, different means of extermination must be practiced, always remembering that all living things are tender and die most easily when they are young; and also that in every case the chief end is to prevent reproduction of kind.
Weeds, like all other plants, may be classified according to the length of time they live: as annual, surviving the winter only in the seed; as biennial, storing in fleshy root or broad green leafy rosette the food drawn from the soil and air during the first season, to perfect the fruitage in the second year; and as perennial, surviving through many seasons and springing up to spread abroad their kind and pester the land year after year, unless destroyed "root and branch." Purslane and the common Ragweed are good examples of the first class, Burdock and Wild Carrot of the second, and Field Sorrel and Canada Thistle of the third. Some plants that round their life-cycle in a year are known as "winter annuals"; the seeds that have matured during the summer germinating in the fall, making a certain growth before the closing in of winter, and completing their development in the next summer. To this class belong the hated Penny Cress, or Frenchweed, the Corn Cockle, and the Field Gromwell or Wheat-thief. Obviously, the best time to compass their destruction is in the spring, before they can develop fruiting stems. Spring plowing or harrowing is of course in order, but it is with such plants as these that the newer method of killing with a chemical spray, or herbicide, is most successful, particularly when they appear in grain fields. The grains are resistant to injury from the spray, for, being "center growers," they make a swift recovery from the slight harm received on outside sheath-leaves, while the tender, outspread foliage of the weed seedlings is often totally destroyed.
Tools For Destroying Weeds
1. Broad-bladed Hoe. 2. Warren Pattern Garden Hoe. 3. Grubbing Hoe. 4. Rake. 5. Weeding Hoe. 6. 7.11.Hand Weeders. 8 SpadingFork. 9. Root-digger. 10. Spud. 12. Spade. 13. Weeding Harrow with shafts and teeth adjustable. 14. Cultivating Hoe. 15. Plow. 16. Cultivator, with adjustable blades of different size. 17. Wheel Hoe.
For biennials, also, the one sure means of destruction is prevention of seeding. Where plowing out is impracticable, frequent cutting must be practiced, in the first season spudding out or cutting off the rosettes, or crown leaves, and in the second season mowing off the flowering stems before the formation of seed.
Perennial weeds are by far the hardest to fight, sometimes requiring the cultivation of special hoed crops in order to insure their complete eradication. The plowing and harrowing given to ordinary field crops often only stimulate the growth of these pernicious plants by breaking or cutting the long-lived underground stems and inducing them to send up new shoots. It should be remembered that their food reserves are in fleshy or woody roots, underground stems, bulbs, or tubers, and that the growth above ground never seems to exhaust these hidden stores of nourishment. However, there is a time when they are most vulnerable to attack, and it is just at that stage of growth when flowering stems are nearing full size, but before the formation of seed. They should then be plowed down, or, if too tall for that, first mowed and then plowed under. Any and every plant, even the sturdiest tree, must die if kept deprived of leaves during the growing season; for it is in these green laboratories that the food gathered from soil and air is so changed and assimilated as to become available for the making of new plant substance. Without leaf-growth the roots must die.
 
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