BULLETIN NO. 45. 
The evergreen Rhododendrons in the Arboretum have never bloomed 
more fully than they have this year and the clusters of flowers and 
the individual flowers have never been larger. The flowers of some 
of the early flowering species and varieties have already passed, but 
those of many of the most important plants are still in good condition 
and others are still to open. 
The hardiest in this climate of all the large-flowered Rhododendrons 
is R. catawbiense, an inhabitant of the upper slopes of the highest of 
the Appalachian peaks on which it grows in great quantities at alti- 
tudes between five and six thousand feet. It is a wide, low, round- 
topped, compact shrub with broad, dark green leaves and rose-purple 
flowers of a rather disagreeable color. There are a number of plants 
of this Rhododendron brought from North Carolina now in flower in 
the collection. This species is one parent of the race of hybrid Rho- 
dodendrons which are usually cultivated in northern gardens and prac- 
tically the only evergreen Rhododendrons found in those of the north- 
eastern United States, with the exception of another species of the 
eastern states, R. maximum. This race of hybrids has been made by 
crossing R. catawbiense with some of the species from the Himalayas, 
chiefly probably with R. arboreum, with R. maximum , and in the 
early days of Rhododendron cultivation in England with the Cau- 
casian R. ponticum. These catawbiense hybrids, as they are called, 
are hardy and valuable in this country in proportion to the influence 
on them of R. catawbiense. 
Rhododendron maximum , which grows naturally as far north as New 
England, is of course perfectly hardy; it has long and very handsome 
leaves, and the pale pink or pink and white flowers are beautiful in 
color, but they open so late that the flower-clusters are much hidden 
by the young branches which have grown from buds below the flower- 
bud before the flowers open, while in R. catawbiense and its hybrids 
these branches do not begin to grow until after the flowers have faded. 
Several hybrids between R. maximum and R. catawbiense are in cul- 
tivation. One of these, known as R. delicatissimum, is one of the 
hardiest and most beautiful of all Rhododendrons which can be suc- 
cessfully cultivated in this climate. As a rule hybrids of hardy plants 
are as hardy as their parents, but this is not always true of R. cataw- 
biense-maximum hybrids, for some of these, like R. wellesleyanum 
and several raised in the neighborhood of Boston, are not very hardy, 
a fact due no doubt to some tender strain in the Catawbiense parent, 
itself a hybrid. 
Two other species of the southern Appalachian region are also hardy 
here, R. carolinianum and R. minus , or, as it has been more generally 
called, R. punctatum. These are small shrubs with small dotted leaves 
and small clusters of pink flowers. The differences between these two 
plants have only recently been understood. R. carolinianum is an in- 
habitant of high altitudes, with handsome dark green leaves, and flow- 
ers which open and fade before the young branches begin to grow, 
and therefore are not hidden by them. This is perhaps the handsomest 
of all the dwarf Rhododendrons which can be successfully grown here; 
it has been out of bloom for several weeks. R. minus is a plant of 
lower altitudes, with smaller leaves and flowers and more open habit, 
and the small flower-clusters are much hidden, like those of R. maxi- 
mum, by the young branches which rise high above them. 
