Bench heating, aka root zone heating.
http://preview.tinyurl.com/yz7qnq5
http://preview.tinyurl.com/ykt425d
http://preview.tinyurl.com/yjpwdfy

which are the long, fractured URLs below:

http://www.rngr.net/Publications/fnn...rsery-notes-2/
2007-winter-forest-nursery-notes/root-zone-heating-can-save-energy-by-
reducing-needs/file


http://www.hrt.msu.edu/energy/Notebo...nderbench_Heat
ing_Systems_by_Bartok.pdf

http://www.umass.edu/umext/floricult...reenhouse_mana
gement/jb_root_zone_heat.htm