106 HORTICULTURE FOR SCHOOLS 



It can be grown successfully as a winter crop in the South. 

 When the head begins to form, the leaves of the plant are 

 brought together around the head and tied to protect the 

 flowers from sunburn and to keep the head light in color. 

 When the heads are fully formed, they remain in best 

 condition only a few days, and must be harvested promptly. 



170. Spinach. Among plants used for greens, spinach 

 easily takes the lead. Spinach requires cool weather, a rich 

 soil and plenty of water. In the South it may be planted in 

 the fall and grown as a winter crop, but in the North it is 

 usually planted in the spring. It may be harvested as soon 

 as the leaves attain sufficient size for handling. 



171. Other plants used for greens are sea-kale, beets, 

 chard, dandelion, and mustard. Some of these grow wild in 

 profusion, but they are much larger when cultivated. 



172. Celery is one of the leading salad plants. It prob- 

 ably originated in England. It is cultivated to a great extent 

 in Europe and America. A large amount of celery is produced 

 in the states of New York, Massachusetts, Pennsylvania, 

 Michigan, Ohio, California, and Florida, and in the provinces 

 of Ontario and British Columbia in Canada. 



Celery requires a cool climate, an abundance of water, and 

 a soil rich in organic matter. It grows very successfully in 

 muck soil. Celery seeds are usually sown in flats, and covered 

 very lightly with soil. A few days after the seedlings appear, 

 they are removed to other flats in order to give each plant 

 more space. In about three months, they are transplanted 

 from the flats into the field. Early celery is set out in the 

 spring. For a late crop, celery is planted in summer. In 

 any case, the celery must be blanched. With the early crop 

 this is usually accomplished by means of boards placed on 

 both sides of the row to shade the plants. The late crop is 

 blanched by piling up soil around the plant, leaving only the 

 top leaves exposed (Fig. 76). Another system of blanching 

 celery consists in setting it so closely that the tops shade 



