FROST PROTECTION IN LEMOoST ORCHARDS. 



29 



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From the data secured in these plats and from o})scrvations made 

 in other orchards it appears that the Lisbon variety, probably owing 

 to its dense foliage and more compact habit of growth, was not quite 

 so susceptible to frost injury as the Eureka. These observations 

 apply entirely to groves which are not protected by orchard heaters. 

 In well-protected orchards there were comparatively small numbers 

 of frozen lemons of either the Eureka or Lisbon variety. It therefore 

 appears that, although in un- 

 protected orchards undersimilar 

 conditions, a greater amount of 

 injury is found in Eureka than 

 in Lisbon orchards, the differ- 

 ence is not sufficiently great to 

 warrant any positive statements 

 concerning the comparative 

 hardiness of the two varieties. 



SUMMARY. 



Extremely low temperatures 

 during December, 1912, and 

 January, 1913, caused serious 

 damage and loss to unprotected 

 lemon orchards in many sections 

 of southern California. 



Detailed records of the pro- 

 portion of merchantable and 

 frozen fruits produced in five 

 heated and five nonheated acre 

 plats of Eureka and Lisbon lem- 

 ons during the calendar year 

 1918 and in two comparative 

 plats during the calendar year 

 1914 in the Corona, Calif., lemon 

 district are presented in this 

 bulletin. 



These data show that in or- 

 chards which were protected 

 with an adequate supply of heaters during the cold weather of 1912-13 

 a large percentage of merchantable fruit was saved and harvested 

 throughout the year. 



In orchards which were not heated a large proportion of the lemons 

 picked during the first six months following the freeze were frozen or 

 unmerchantable, and the trees did not return to normal production 

 until a year had elapsed. 



Fig. 15. — Diagram prepared from the figures presented 

 in Table XXII, showing the percentages of mer- 

 chantable and frozen fruits produced on the non- 

 heated acre of Lisbon lemon trees, plat 2, as com- 

 pared with the nonheated acre of Eurelia lemon trees, 

 plat 3, during the calendar year 1913. 



