Perry's Perennial Pages

Vermont Winter Soil Temperatures

Dr. Leonard Perry, Extension Professor, University of Vermont

For over 16 years I have monitored soil temperatures in field perennial beds, at various locations, depths, and combinations of mulch in USDA zone 4 in Milton VT, in a loam soil. The following were taken at a depth of 2 inches similar to many perennial crowns, with no mulch except for natural snow cover. Some years, or specific data a certain year, were not available for various reasons (or not below 32ºF), yet sufficient results over this period should provide useful information. Data was collected for the first time temperatures dropped below (1st<40ºF), or rose above (1st>40ºF) 40ºF, and when they stayed below this (<40ºF) or above this (>40ºF) generally beginning in mid to late October. For many perennials, around 40ºF is believed the temperature at which roots are reported to stop growing.
 
Year 1st<40ºF <40ºF <32ºF 1st>40ºF >40ºF
08-09 10/8        
07-08 11/8 11/13 (1/10) 12/1 (1/8) 4/1 4/30
06-07 11/20 1/7 -- 3/25 4/18
05-06 11/9 12/2 2/11 3/14 4/11
04-05 11/6 11/26 12/30 3/24 4/16
03-04 11/8 12/1 1/9 3/26 4/16
02-03 -- 11/23 1/5 3/18 4/26
01-02 11/10 12/8 -- 3/9 4/13
00-01 11/8 11/17 12/6 -- 4/29
99-00 11/1 12/10 12/26 3/23 4/1
98-99 11/4 12/22 -- -- --
97-98 11/4 11/13 1/3 3/17 4/13
96-97 -- 11/17 1/1 -- --
95-96 10/26 12/2 12/30 3/15 4/22
94-95 -- 1/22 -- 3/8 --
93-94 10/14 12/1 12/16 3/30 --
90-91 10/27 11/25 12/31 3/16 4/22
89-90 11/5 11/17 11/29 3/11 4/19
           
Average 11/3 12/4 12/29 3/18 4/17
Range 10/14-11/10 11/13-1/22 11/29-2/11 3/8-3/30 4/1-4/29



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