160 Gardening 
The eight lines drawn mark off into zones that part of 
the United States east of the Rocky Mountains. In 
each of these zones the range of planting dates in spring 
averages about the same. The earliest dates for plant- 
ing the various vegetables in these zones are given in the 
table on pages 348 and 349. There are, of course, local 
conditions, such as elevation, drainage, and the slope 
of the land, not indicated on a map of this kind, which 
change somewhat the planting dates as given. Each 
gardener must find out for himself the more exact 
planting dates for his own locality and his own gar- 
den. 
The western part of the United States is broken by 
mountains and streams, which cause so much irregularity 
in the frost dates that it is not possible to mark out this 
area into definite planting zones. 
The killing frosts of autumn. The first severe frost 
in autumn kills most garden plants. Tomatoes, corn, 
beans, peppers, and eggplants are killed or badly in- 
jured ; beets, carrots, cabbages, lettuce, turnips, pe-tsai, 
celery, endive, and kale are not severely injured and may 
be left in the garden until just before the ground is frozen. 
Parsnips and salsify can be left in the ground over winter, 
but even these more hardy plants practically cease 
growth with the coming of severe frosts. 
In planning for late or autumn crops, and especially 
for the succession crops, the gardener should know (1) 
how long a period is required by the particular crop to 
mature, and (2) when the first killing frosts are to be 
expected. This is especially important in the northern 
states, where frosts come earliest. 
