34 



have been established that it is probably the intensity 

 rather than the quality of light which is required for 

 flower production. Another factor which is important in 

 this respect is the concentration of organic material in the 

 stem and leaves of the plant ! , while an increase of water 

 and inorganic salts tends to the development of foliage 

 rather than flowers. It is for this reason that a reduction 

 in the supply of water is so helpful in producing abundant 

 flower buds. It is sometimes thought that a wealth of 

 blossom on our fruit trees predicts a fine summer, from 

 what has been said above, it is obvious, however, that it is 

 the fine summer or dry autumn of the previous year which 

 is responsible for the prolific bloom. Flower buds on our 

 fruit trees are, of course, already developed in the late 

 autumn. Dealing with herbaceous plants, it has been 

 found possible to arrest the development of flowers even 

 if the flowering shoot has commenced to make its appear- 

 ance. Thus in specimens of the common House Leek a 

 rosette of vegetative leaves may be caused to appear on 

 the flower shoot if the plant is copiously watered and 

 illuminated with light passing through a red or blue 

 screen. Conversely, the runners of some plants may be 

 made to bend upwards and develop flowers if water is 

 withheld and the plant placed in a very bright light. 



The horticultural practice of pruning and root pruning 

 is also intended to further floral development. Each tree 

 or shrub must be treated differently according as to 

 whether flowers normally make their appearance on long 

 shoots or on spurs, i.e., on new or old wood. The removal 

 of non-flowering shoots is therefore what is aimed at. In 

 summer pruning the stoppage of the growth of purely 

 vegetative shoots will actually stimulate the older 

 branches to form flowers, as they will have an increased 

 amount of food material at their disposal. The increased 

 production of flowers effected by root pruning is often 

 remarkable. It will be sometimes observed that apple 

 and other fruit trees produce long and vigorous new 

 shoots, particularly in an upward direction, which are 

 caused by the development of deep roots able to obtain 

 an abundant supply of water even in fairly dry soil. The 

 removal of these deep roots stimulates the growth of 

 fibrous roots in shallow soil, where there is a less abundant 

 supply of water in the summer and early autumn; the 

 result of root pruning is therefore the production of 



