
Map of Climatic Zones from Manuai of Cultivated Trees and Shrubs by Alfred Rehder 
of Arnold Arboretum. The figures at ends of lines separating the zones show lowest 
average temperatures of the coldest single month on record. Look at page 6 and you 
will appreciate how elevation, air drainage, water bodies and other local conditions 
may have much influence in affecting the way trees will survive in particular locations. 
Therefore this map is only an approximate guide. The heavy line (170) marks average 
length of frost free season of 170 days. Lewisburg, Pa., is just above it on the Susque- 
hanna River. Note this line again near Great Lakes. Remember that this line is an 
average. Some seasons are shorter and some are longer. In Pennsylvania, a careful 
study of the records shows that in one-fourth of the years the growing season is three 
weeks longer than the average. That fact makes it possible for a Pecan tree to come 
through with an occasional crop much farther north than it can be depended upon to 
ripen its nuts. But tt is an ornament every year. So is every other tree on our list. 
The Northern Pecan 
If you want to make your place a dis- 
tinguished landmark, plant two balanced 
Pecan trees of the same variety and give 
them a chance. I have seen these trees 
towering thirty feet above the tops of the 
oak forests in Indiana. I have seen them 
six feet in diameter, with more than 100 
feet spread. They are truly lordly trees, 
and will bear nuts for centuries. One 
particular tree in southern Illinois was 
full of nuts when the first white man saw 
it in 1817. It is reported that it only 
missed three crops in the next 97 years, 
and it is still going strong. Ordinarily 
Pecan trees, like most apple trees, alter- 
nate their heavy and light crops. 
Many think of the Pecan as a southern 
tree because trees producing fine nuts 
were propagated in the South and the in- 
dustry started in the Cotton Belt. But 
the Pecan tree grows wild and ripens its 
nuts in southeastern Iowa, in south- 
western Ohio, and thence downstream to 
the Gulf of Mexico. George Washington 
called them “Illinois nuts” because the 
ones he had came from Illinois. He is said 
to have been very fond of them, often 
carried them in his pocket and ate them 
at unexpected times. His diary reports the 
planting of these nuts, and the trees he 
planted at Mount Vernon are still 
thriving. 
