Weed and Characteristics of Weeds

weed : 

Any plant not sown in the feld by famer is out of place, called weed.

 The term, 'weed' used by Jethro Tull for the first time, suggested an useless and harmful plant that persistently grows where it is quite unwanted.

According  to Robinson weed: 

Weeds are that species of plants which grow unwanted or are not useful, often prolifc, persistent, interfere with agricultural operations, increase labour cost and reduce the crop yields.
Weed is a plant growing where it is unwanted plan. out of place, extremely noxious, useless, poisonous.

Characteristics of weeds :
Weeds are like any other crop plants in size, form, morphological and physiological characters but posses the following characteristics, on account of which they are considered as enemey of crops by the famer.
1) The weed seeds geminate earty and the seedlings grow faster. They being hardy, compete for light, moisture and nutrients.
2) They flower earlier, run to seed in profusion and mature ahead of the crop.They are difficult to control and it may be even impossible to eradicate some weeds completely.
3) They are non-useful, unwanted and undesirable.

4) They are hamful to crops, cattle and human beings.

5) They can thrive even under adverse conditions of soil, climate etc.

6) They are prolific and have a very high reproduction capacity e.g. A plant of satyarashi (Argemone mexicana) produces over 5000 seeds while a plant of striga produces over half a milion seeds.

7) Viability of weed seeds remain intact, even if they are burried deep in the soil.

8) The seeds may have speciak structure like wings,spines , hooks, sticky hair etc. on account of which they can be easily disseminated over long distances.

9) Many weeds like Cynodon dactylon are vegetatively propagared and spread rapidly all over the field even under adverse conditions.