302 Notes on Greenhouse Plants, ^c. 



of the Sim, when cooled down and collected in the form of 

 rain, has none of those impurities with which it is impreg- 

 nated when filtered through the soil. On the contrary, it 

 contains ammonia, carbonic acid, and other matters highly 

 beneficial to vegetation. 



We have very frequently been asked the question, " How 

 often do you water your plants ? " and our answer has as 

 frequently been, ivhenever they are dry. Sometimes it may 

 be twice a day, at others once a week. It is evident that no 

 direct answer can be given to such a question. A plant 

 newly potted requires less water that it did before, because 

 there is a large amount of soil about the roots; as these 

 extend, they suck up more moisture and occupy the pot ; 

 consequently the soil will sooner get dry, and when the roots 

 get crowded, much more will still be necessary. During 

 dull, damp weather, there is less perspiration by the leaves, 

 and less absorption by the roots. Again, during bright sun 

 and dry atmosphere, absorption is the most active ; and that 

 to a greater extent in plants presenting a broad surface of 

 leaves, than in small-foliaged species. Hence the necessity 

 of careful watering to heaths, epacris, and others of like 

 habit, with small foliage and delicate roots. We are very 

 much inclined to suspect that this is the principal reason why 

 these and others of the most beautiful hard-wooded exotics 

 are so seldom found in greenhouses. The application of 

 water, rightly understood, is the most powerful controlling 

 influence we possess over vegetable groAvth. By limiting 

 the supply, we can produce a state of rest, hasten the devel- 

 opment of flowers, the ripening of fruit, and, other things 

 being equal, these conditions are reversed by a bountiful 

 supply. 



With regard to the proper time for watering plants, the 

 general practice is to water in the morning or early part of 

 the day during the winter season, and in the afternoon or 

 evening during summer. In cold weather, early watering 

 allows excess of moisture to evaporate before evening ; hence 

 the plants are better enabled to withstand moderate cold. 

 When artificial heat is in constant requisition, a certain 



