TEMPERATURE, LIGHT, AND MOISTURE 123 



Blanching. Plant parts produced in darkness are paler and 

 tenderer than when grown in the light, and this fact gives 

 reason for the process known as blanching. Plants may be 

 blanched by heaping up the soil about them, or by covering 

 them with boards, tiles, or anything else that will exclude 

 light. Celery and sea kale are always blanched for the table 

 in this way, and asparagus often is. Endive is blanched by 

 tying the outer leaves 

 over the center a few 

 weeks before using, and 

 by the same method 

 the heads of cauliflower 

 are protected from the 

 light and kept white. 



Protection from light. 

 Light and heat are so 

 closely allied that what 

 will protect from one 

 will usually protect 

 from the other. The 

 lath house, built of com- 

 mon lath or of wider 

 strips separated from 

 one another by suffi- 

 cient space to admit 

 some of the light, is 



often used for growing shade plants, slow-growing seedlings, 

 and similar specimens. In addition to this protection from 

 light and the attendant heat, the lath house retains the 

 moisture in the air. Artificial shading by means of thin cloth 

 or lath screens is frequently employed in the cultivation of 

 tobacco, coffee, pineapples, and ginseng. In summer radishes 

 and lettuce come to much greater perfection when grown in 

 the shade. 



Photograph by the University of Illinois 



FIG. 88. Cauliflower plant 

 The leaves are tied above to blanch the center 



