The area features a frost-free period
for seed corn production that rivals the Midwest United States, with temperatures and precipitation moderated by the surrounding Great Lakes.
In North China Plain, the temperature falls to 5 degrees below zero, even lower in winter with a frost-free period
of around 190 days.
Dandelion roots can be harvested during any frost-free period
of the year and eaten raw, steamed, or even dried, roasted and ground into a coffee substitute.
Accordingly, the frost-free period
fluctuates from 125 to 175 days.
Because the Carolina wren's winter range is conditioned by the average minimum January temperature and the mean length of the frost-free period
, the expansion of its winter range is often cited as an indicator of climate change.
TABLE 1.--Location, habitat and selected climatic features of the Vaccinium corymbosum sampling sites in North America North Carolina, Site: Florida, ABS NC Latitue/longitude (N/W) 27[degrees]17/ 35[degrees]07/ 81[degrees]21' 83[degrees]15' Elevation (msm) 40 1170 Annual precipitation (mm) 1374 1125 Frost-free period
(days) 330 150 Min.
acclimate allelochemical allomone annual biennial bolt companion planting cool-season crop frost-free period
frost-sensitive frost-tender frost-tolerant harden-off heat-hardy kairomone olericulture perennial pheromone semi-hardy very hardy
The frost-free period
is the average number of days from the last spring frost to the first frost in the fall.
PREPARE the ground for new trees and shrubs in a frost-free period
. Grass is bad for young trees as the roots produce a substance that inhibits tree growth.
In 1967, Agriculture Canada scientists created a plant hardiness map for Canada using plant survival data and a wide range of climatic variables, including minimum winter temperatures, length of the frost-free period
, summer rainfall, maximum temperatures, snow cover, January rainfall and maximum wind speed.
The longer-range forecast from the London Weather Centre is also for a mild, frost-free period
with the odd shower.
Much more important is pruning at the right ti Small branches up to one inch in diameter, or 5pc the total crown, whichever is less, and dead wood any size can be removed at any time of the year with problems although the pruning of box hedges must confined to frost-free periods
because of the risk frost damage to the freshly-cut surfaces.