- 2 



plants may be severely injured or killed when exposed to 10°F, 

 while blossom primordia in the cro\>ms may be injured at 25°F. A 

 good rule to follow is to mulch after several days of near-freez- 

 ing temperatures, but prior to severe cold. 



Many materials are used for mulch. They should be free of 

 weed seed, and be loose and light so as not to mat down, but heavy 

 enough so that it will not blow away. Canadian researchers (2) 

 found straw provided better protection than sawdust or wood chips. 

 Marsh hay appears to be as effective as straw. Both of these ma- 

 terials lose much of their insulative properties when they become 

 wet, ice-filled, or matted down. 



We have monitored strawberry crown temperatures under several 

 mulching treatments (Table 1). 



Table 1 . Minimum air temperatures, minimum temperatures of straw- 

 berry crowns of mulched and unmulched plants, and snow depth. Data 

 were collected in 1966 and 1975. 



Air temp. Snow depth Straw mulch 



C°F) (inches) (tons/A) 



197 5 



-6 8 3 



-6 8 6 



-6 8 



-6 



1966 



-18 6 



-18 



-12 7 6 



-12 7 



With an air temperature of -6% plant crown temperature was 

 27°F under both 3 and 6 tons of straw/A, with 8 inches of snow 

 cover. Plants with 8 inches of snow but which were not mulched 

 had crown temperature of 24°F. Plants that were not mulched and 

 lacked snow cover were at 3°F, which is below the critical temper- 

 ature for strawberry plants. Crown temperatures are influenced by 

 the present temperature as well as the temperature of several pre- 

 vious days. For example: in 1975, there were 5 consecutive days 

 when the temperature fell below 15°F. The next day was -6°F and at 

 that time the crown temperatures were 3°F. In 1966, however, sever- 

 al warm days followed by a temperature of -18°F produced a higher 

 crown temperature of 5°F. 



The data in Table 1 suggest that mulch provides little addi- 

 tional protection when plants are covered with 7 inches or more of 

 snow. Whfen snow cover is lacking, however, 6 tons of straw per 



