204 CALIFORNIA VEGETABLES 



The period of growth at which the crop should be harvested 

 depends largely upon the season, market requirements and prices. 

 The California market demands a large solid head and the crop 

 should remain in the field until it has reached this condition. 



Chief Lettuce Troubles. A good full field or garden bed de- 

 pends upon good seed and careful attention to cultural require- 

 ments which have been outlined. 



During winter and spring, especially on heavy soils, there is 

 danger of stem-rot. The plants become sickly yellow and the stems 

 rot at the surface of the ground. Diseased plants may appear 

 scattered throughout the field, or in well-defined areas. This is a 

 fungus disease which thrives best under excessive moisture condi- 

 tions. For control improve the drainage and make the beds high 

 enough so that the water will not stand directly around the plants. 



Sunburn is manifested by a blackening of the edges of the 

 leaves inside the heads. The cause is a period of excessive hot 

 weather from the time the plants are half-grown until they have 

 commenced to head. Planting in the fall or early spring will largely 

 control this disease; if the weather is very hot and dry during the 

 spring the plants should be irrigated frequently. 



Failure to produce solid heads is caused either by a poor 

 quality of seed, an insufficient supply of moisture, or unfavorable 

 climatic conditions, such as excessive hot weather while the plants 

 are maturing. Use only well selected seed and apply sufficient moist- 

 ure at the time the heads are maturing. During the late spring 

 when the weather is hot the crop should be harvested immediately 

 after the heads have matured. 



Varieties. There is almost illimitable variety in lettuce, and 

 inextricable confusion in the nomenclature resulting from renaming 

 by seedsmen and others. As with other plants, however, a few va- 

 rieties constitute the bulk of the California lettuce product. It is 

 customary to arrange lettuce varieties in two groups ; one has round- 

 ish heads and includes the "cabbage" varieties; the other has elon- 

 gated heads and includes the "cos" varieties. There is, of course, 

 much difference in the density of the heads, and some are quite loose 

 and open, but the close-heading varieties are better and the more 

 suitable for market handling. In California the cabbage varieties 

 very largely preponderate over the cos varieties, and the non-head- 

 ing or "cutting lettuces," or curled varieties, are not widely grown, 

 though they may be found useful in getting the quickest foliage from 

 the seed sowing. It should be noted that compared with the cab- 

 bage type, the cos lettuce is hardier and less susceptible to frost; it 

 also shows more ability to withstand drought and is also less liable 

 to sunburn, the last two features making it better adapted to hot 

 and dry localities, while the first is one which especially recommends 

 its use as a late kind. And yet the firm-heading varieties are over- 

 whelmingly superior commercially and are secured by growing 

 them in different districts at seasons of the year which afford the 



