COMPLIMENTARY 
NEW SERIES VOL. VllI 
NO. 5 
ARNOLD ARBORETUM 
HARVARD UNIVERSITY 
BULLETIN 
OF 
POPULAR INFORMATION 
JAMAICA PLAIN. MASS. MAY 12. 1922 
American Hawthorns. Some of these plants are now in bloom and 
the flowers of others will be conspicuous in this Arboretum during the 
next six weeks, and from the middle of August until midwinter Haw- 
thorns will be brilliant here with fruit. No other group of plants is 
represented in the Arboretum by so many species; and no other group 
of small trees and shrubs with deciduous leaves can add so much beauty 
during such long periods of the year to our parks and gardens. The 
discovery, determination and cultivation of the large majority of these 
plants has been accomplished during the last twenty-three years. For 
until the end of the last century no one had formed any conception of 
the number, variety and distribution of these plants in North America. 
To the botanists of forty years ago fifteen or sixteen species with two 
or three varieties were known, and American gardeners were able to 
plant only two or three of these. There are now some five hundred 
species or forms established in the Arboretum, and an increasing num- 
ber of these trees are flowering and producing their fruits here every 
year. Hawthorns are distributed in North America from Newfoundland 
and northern Quebec to northern Florida and northern Mexico, and 
from the Atlantic to the Pacific. They are much more abundant in 
species east of the eastern borders of the great plains than in the 
Rocky Mountain and Pacific regions, where they range northward into 
British Columbia and southward only into northern California. So far 
as is now known they are most abundant in species in the valleys of 
the streams which flow from north and south into Lake Erie, and in 
the region which extends from southern Missouri to the valley of the 
Red River in Arkansas. New York and Pennsylvania are rich in 
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