First, we have the ordinary weeds of cultivated grounds. 

 These plants doubtless migrate into my garden every year from 

 my neighbors in all directions, or from street-sides and vacant 

 lots, and for that matter, from my place to my neighbors as well. 

 We are all very generous with our weeds. If by careful work I 

 exterminate one species completely, I know it will be back next 

 year anyway. There is no hope for their permanent banishment. 

 All we can do is try to keep their numbers down to a minimum. 



These common weeds we shall have to classify further into 

 those of flower-beds, hoed ground, and the bare soil under 

 shrubbery, and those of the lawn. The two groups are quite 

 distinct in species. 



In the beds and shrubbery the commonest weeds are the 

 sorrel (Oxalis cyniosa), the chickweed, galinsoga, nimble Will 

 {Muhlenhergia diffusa), and wandering Jew, all of which tend 

 to spread into the shadier edges of the lawn. Others which are 

 present every year but do not constitute a serious menace are 

 shepherd's-purse, foxtail, carpet weed, and purslane. 



Galinsoga is an interesting weed, and I believe it would 

 repay some careful experimentation. Seeds which have passed 

 the winter refuse to germinate until the ground is thoroughly 

 warmed in late spring and then grow to a fair size before bloom- 

 ing. Seeds produced during the summer germinate immediately, 

 even until after frost. As the days become shorter in late sum- 

 mer and early fall, so does the life cycle of the plant, until in 

 October it may set seed when only an inch high. Is this an effect 

 of temperature or is it due to the shorter period of daylight? 

 And if the summer seeds germinate so quickly, why do not all 

 of the seeds germinate the same year, the later ones taking 

 advantage of the warm days of Indian summer? Obviously, if 

 they did, we would not have galinsoga with us much longer. I 

 commend the plant to my colleagues at the Boyce Thompson 

 Institute for study. 



Numerous other weeds are sporadic in appearance, easily 

 eradicated, and not always developing in successive years. Such 

 are the fieabanes (Erigeron ramosus, annuus, and canadensis), 

 smartweed, cinquefoil (Potentilla monspeliensis), red sorrel, 

 Canadian blue grass, pepper grass, and wild carrot. I have seen 

 single plants only of Spanish needle (Bidens vulgata,) tumble- 

 weed, ground ivy, and burdock. A single plant of another cin- 



