CULTIVATION OF CITRUS GROVES. 281 



and at the sides long after the last drop is visible. Some 

 of it, too, is being drawn back to the surface and thence 

 evaporated into the warm air. Irrigation after sundown 

 has some distinct advantages, if the water can be handled. 

 Sub-irrigation upon soils adapted to its use is the ideal 

 system of applying water, and greatly lessens waste. 

 Orange roots will not enter a pipe-line, unless it is full 

 of water all the time. If the pipe is on a grade and open 

 at bottom and top so that air passes through it, there will 

 never be trouble from orange roots. Valves, once thought 

 necessary, are not now used. The high cost of the present 

 sub-irrigation systems places them beyond the reach of 

 most orange growers." 



Cultivation in Relation to Dormancy and Frosts. 

 In regions subject to frost every effort should be made 

 to have the trees in a perfectly dormant condition during 

 the period when frosts are likely to occur. Citrus trees 

 are notoriously responsive to slight elevations of tem- 

 perature during the winter months. In a perfectly dor- 

 mant condition they will withstand a considerable de 

 gree of cold, but if the sap is moving, a very slight degree 

 of cold may injure them seriously. 



Unfortunately, they cannot be put in a complete state 

 of dormancy, to remain so throughout the winter despite 

 changes in temperature. Still, something may be done. 

 Fertilizers, particularly those rich in nitrogen, which 

 have a tendency to prolong the growth of the tree, should 

 not be applied late in the season. Cultivation should 

 not be continued late into the fall, as the stirring of the 

 soil tends to cause the trees to grow late into the autumn. 



All cultivation should be discontinued early. Grass 

 and weeds should not, however, be allowed to remain in 

 the grove during the winter months. If open fires are 



