PEAS AND PEA-LIKE PLANTS 443 



532. Adaptations. Field peas are adapted only to 

 moderate temperatures ; and while they will withstand 

 heavy frosts, they quickly succumb to high temperatures, 

 especially if combined with humidity. As their period 

 of growth is short, 60 to 100 days for hay, 80 to 120 days 

 for seed, they may be grown as summer crops in the 

 North, winter crops in regions where the temperature 

 rarely falls below freezing and spring or fall crops in 

 intermediate areas. The non-adaptation of field peas to 

 heat is frequently seen as far north as Maryland, where 

 the crop is often severely injured by hot weather in May. 

 Their preference for a cool growing season has led to their 

 being much more extensively grown in Canada than in the 

 United States, 



Field peas are not particular in regard to humidity, 

 thriving well both in humid and in semi-arid regions, but 

 they succeed best in regions of moderate rainfall. 



They do best on loams or clay loams, but will succeed 

 on most soil types, if well drained. Like the majority 

 of leguminous plants, they prefer an abundance of lime in 

 the soil. 



533. Importance. Field peas are more important in 

 Ontario, Michigan and Wisconsin than in any other 

 states or provinces. To some extent they are grown in 

 most of the northern tier of states in the Union and in 

 all the southern provinces of Canada. In 1909, there 

 were in Ontario, 258, 461 acres ; in Michigan, 94,932 acres ; 

 and in Wisconsin, 78,017 acres. 



534. Agricultural varieties. The varieties of field 

 peas are very numerous, probably numbering over 100 

 and not including any of the more numerous sorts of 

 garden peas. 



Varieties differ in such characters as degree of earliness. 



