VEGETABLE GARDENING, OR OLERICULTURE 5 



extent, to overcome the bad results from insect pests and plant 

 diseases. With such crops as cabbage, cauliflower, kale, and tur- 

 nips, all of which are subject to the same class of diseases and the 

 same insect enemies, it frequently becomes necessary to abandon 

 for a number of years the land on which such crops have been 

 grown, until the organisms which produce the diseases become 

 starved out. The clubroot of cabbage forms one of the very best 

 examples of this type of plant disease. The wilt of the muskmelon 

 and cucumber and the wilt of cotton are also diseases of this 

 nature. They are diseases which, because of their ability to perpet- 

 uate themselves from year to year in the soil, and because they 

 develop in the interior of the plant tissues, cannot be successfully 

 treated by external agencies. The only known remedy for them is 

 to starve them out by not growing the host plants upon the infested 

 soils for a series of years. 



Succession of crops. A succession of crops is, as a rule, of 

 more importance to the market gardener than to the truck grower. 

 Because of the proximity of the market gardener to the markets 

 which he supplies, he can afford to plant in succession so as to 

 prolong the season for his crops, particularly if he is supplying 

 a local market which depends largely upon home production. The 

 market gardener at the North can afford to make three or even 

 four plantings of peas, three or more plantings of string beans, 

 the same of beets, and so on through the list, while for the South- 

 ern grower the only safe way is to plant a large quantity at one 

 time, which will give him a sufficient product to enable him to 

 ship large consignments carload lots to one or more of the 

 great cities at a particular period. A succession of plantings of the 

 same crop is therefore of little moment to the truck grower who is 

 at a distance from his market. What he desires is a variety of 

 crops which follow one another, and which will not meet severe 

 competition in the market to which he is catering. In order to 

 accomplish this and at the same time utilize the land to the best 

 advantage, truck growers frequently have two different crops grow- 

 ing upon the soil at the same time. A common arrangement is to 

 plant strawberries and potatoes upon the same land at the same 

 time. The potato crop will be harvested early in the season, and 

 the entire area then becomes available for the strawberry plants, 



