Some General Observations on Weeds. 



THERE are a great many definitions of weeds. One is " Any useless or 

 troublesome plant." A weed may be a plant which, under different circum- 

 stances, is a useful one. Thus Johnson grass has many merits, but it 

 becomes a weed of a most aggressive kind in a cultivation paddock. Useful 

 plants, which have become scattered amongst a crop, cannot be separately 

 harvested; they thus become useless, and even worse, for they vitiate the 

 main crop. They are therefore weeds. 



Immediately a plant gets out of control in cultivated or pasture land, it 

 becomes a weed. Many are vegetable pariahs ; they have had a bad time, and 

 hence have developed characters which enable them to resist annihilation. 

 Some are especially injurious, and tenacity of life and noxiousness may be 

 combined in the same weed. How important it is, therefore, that we should 

 know our weeds, and to assist in this, some illustrations will help identifica- 

 tion. But an important thing to be kept in mind is that when a new weed 

 appears on the property its identity should be ascertained, and particulars 

 sought concerning it. To be on the safe side, it should be destroyed at once, 

 as if it seeds it may get beyond control. Again, acclimatisation experi- 

 ments with economic plants are full of surprises, and so are the unbidden 

 acclimatisation experiments that weeds undertake in spite of us. It may 

 turn out that a weed may hitherto have not a very bad reputation, but your 

 property may offer special attractions to it and it may spread to an extent 

 never previously recorded. Why run the risk? Keep your property well 

 inspected, and " run in " every suspected weed, adopting the attitude of a 

 policeman towards a suspected person. 



Asa Gray, the American botanist, was a charming short-paper writer, and 

 his " The Pertinacity and Predominance of Weeds," in his Scientific Papers, 

 Vol. ii, p. 234, is profitable reading. 



Following is a synopsis of this series of notes on weeds, and I trust that, 

 the presentation of the points (original to some extent) will be found useful. 



SECTION 1. BAD POINTS OF WEEDS. 



O) They take up the space which should be occupied by useful plants. 



(fr) They screen off light and air and deprive the crop of various manuriat 

 constituents. 



(c) They are harvested with crops which they depreciate. 



(d) Some weeds are parasitic on crops and do not take their sustenance 

 from the soil and air. They thus weaken the crop. Such plants are Dodder 

 and Mistletoe. 



0) Weeds harbour insect and fungus pests. The danger lies in the fact 

 that we may not trouble to apply insecticides or fungicides to weeds, which 

 form a nursery for pests. 



