Prevention of Cold Damage to Container-Grown Longleaf Pine RootsThis article is part of a larger document. View the larger document here.
When longleaf pine (Pinus palustris Mill.) seedlings are container-grown in open fields, their roots may be exposed to damaging, cold temperatures. Major losses in some nurseries have occurred. Between November 1996 and February 1997, we measured the cold hardiness of container-grown longleaf pine roots by measuring electrolyte leakage (a) of greenhouse-grown and growth-chamber hardened seedlings representing minimum and maximum cold hardiness, respectively, and (b) of outdoor grown seedlings. Minimum tolerable root temperature was 25 °F, which varied little with season; a few degrees lower was lethal. Weather records at the W.W. Ashe Nursery near Brooklyn, MS, showed that damaging temperatures occurred on 7 nights per year on average. Covering the seedlings with black plastic overnight held rootball temperatures 10 to 12 °F above ambient air temperature and saved the crop twice in December 1996. However, the best management strategy is to outplant seedlings before the onset of damaging, cold temperatures because once outplanted, the seedlings are safe.