GLOSSARY 367 



Mulch: 



A surface covering about the base of plants to prevent or retard evapo- 

 ration of moisture from the soil, and prevent sudden freezing and 

 thawing in the soil. Dead leaves, straw, manure, etc., are commonly- 

 used. 



Naturalize: 



To adapt and to cause to grow, without artificial care, in a woodland or 

 field environment. This does not imply reproduction of its kind in the 

 new location. 



Nitrification: 



The process resulting in the formation of nitrates in the soil. Certain 

 bacteria known as "nitrifying bacteria" are the cause of this change of 

 nitrogen and nitrogen compounds into nitrates. It is thus the oxida- 

 tion of nitrogen caused by bacteria in the soil. Nitrification cannot 

 proceed except in a moist, warm soil which is well aerated. It is checked 

 entirely when the soil temperature is lower than 40° F. and also when 

 the soil becomes water logged or saturated, and proceeds rapidly when 

 the temperature reaches 75° Fahr. and when only 40 to 50 per cent, 

 of the water necessary to cause saturation is present. 



Nursery: 



A place for growing plants out-of-doors, usually under intensive culti- 

 vation. 



Nursery-grown Stock: 



Plants which have been grown at least one full year in a nursery, under 

 the supervision of competent gardeners or nurserymen so as to pro- 

 duce a number of even-sized superior plants for transplanting. 



Open Allee: 



A way framed on either side by symmetrical rows of closely planted 

 trees or tall shrubs (of a height not less than twice the width between 

 rows), and so maintained that both sides present a continuous vertical 

 wall of close-growing foliage. 



Opening-up: 



In discussions on pruning this term means the cutting out of sufficient 

 growth to admit the sunshine to the centre of the plant or to the area 

 about a group of plants. 



Organic Manure: 



Manure consisting largely of decaying matter of animal or plant 

 origin as distinguished from mineral manures which are inorganic. 



