North American Fruit Explorers mailing list at ibiblio

["Ernest Plutko" <ernestplutko@wiktel.com>]

Jim Fruth writes that he successfully raises zone 5 blackberries in
zone 3 by bending down canes in Fall so canes will be covered by
snow.  Tender grapes vines are also protected this way.  Today when
the air temperature was -8 F the temperature next to the ground under
12 inches of snow was + 18 F.  A little later when the air
temperature was -17 F the temperature next to the ground under 12
inches of snow was +17 F.  We are getting some colder temps the next
few days down to -29 F and I'll measure the ground temp again.  It
will be interesting to see what differences deeper snow, or covering
thermometer with soil or straw or tarp will have on ground temps.