QBARS - v22n1 Rhododendrons After a Hot, Dry Summer in Washington, D.C.

Rhododendrons After A Hot, Dry Summer In Washington, D.C.
George W. Ring, Fairfax, Va.

This is a report on observations of the flower bud set, general vigor and foliage density of more than 250 varieties and species rhododendrons at the U.S. National Arboretum in Washington, D.C. The observations were made in February, 1967 following the hot and dry summer of 1966 during which the temperature reached 90° F, or higher, on more than 50 days. Precipitation during the 3-month period June-July-August was only 4.6 inches compared to a normal of 12.3 inches.

The original intent of the observations was to acquaint the author (a recent enthusiast) with many of the clones already developed by breeders; and to identify those having good flower bud set, vigor, and dense foliage for potential use in breeding new rhododendrons suitable for landscape plantings by the average non-specialist in the Washington, D.C. area.

At the Arboretum, rhododendrons have been established in three different areas. Area 1 has chiefly a southeastern exposure with the least shade of the three. A few of the plants, located on severely hot-dry slopes in this area, were omitted from the observations. Areas 2 and 3 are on a well wooded north-eastern slope. Area 2 is a semi-formal setting of Shammarello hybrids. The largest group of plants is in Area 3 along or near footpaths.

A generalized rating system (legend given below) was used in an attempt to evaluate and classify the visible wide differences in flower bud set, vigor and foliage density. Ratings for the plants in the three areas are presented on the following pages.

R. 'Alice'
Fig. 8.  'Alice', one of the older R. griffithianum hybrids,
exact parentage unknown, introduced by J. Waterer.
It received an A.M. (RHS) in 1910.
Photo by Cecil Smith
Symbols indicating flower bud set Symbols indicating plant vigor Symbols indicating foliage density
H - practically all terminals
V+ - rapid, well branched
D - dense, desirable as an
evergreen specimen.
L+ - sufficient buds for good
flower display.
V - good growth-little or no
evidence of dieback.
S+ - well clothed but airy
appearance, needs
L - scattered buds. A+ - acceptable without
improving conditions.
S - sparse-lanky under
clothed appearance
L- - 1 or 2 buds. A - fair, might improve with
intensive care.
S- - sparse foliage on
oversized branches.
O - none. A- - barely surviving - poor
S - sickly.
Area 1
Flower Plant Foliage Remarks
Buds Vigor
Alice L A S
auriculatum L+ V S
Azor O A S dead branches
Betty Wormald L+ A+ S+
Countess of Athlone L A- D
Cynthia H V S very gangly
Douglas McEwan L+ V
Dr. H. C. Dresselhuys L V+ D
Duke of York L A- S+
Everett H A- S part dead
Faggetter's Favorite L+ A+ S+ dead branches
Fastuosum Fiore Pleno L+ A S+ many dead branches
Graf Zeppelin O A S dead branches
Henrietta Sargent L+ A+ S
Hollandia L+ V D
Kate Waterer L- A- S+
Lady Stuart of Wortley O A S dead branches
Loder's White O A S
Lord Roberts L A- S+ dead branches
Marinus Koster L- A S
Mars L+ A D
Maximum Roseum (Ponticum Roseum) H V S+
Mrs. A. T. de la Mare L A S+
Mrs. C. S. Sargent L+ A D
Mrs. Philip Martineau L A S
Mrs. R. S. Holford L A- S
Mrs. T. H. Lowinsky H A+ S
Mum L A D
Pink Pearl L+ A+ D
Prince Camille de Rohan L+ A D
Prof. Hugo de Vries L+ A+ S
Prof. J. H. Zaayer O A+ D
Romany Chal L A D
Van Nes Sensation H+ V D Outstanding
Area 2
Shammarello Hybrids
Flower Plant Foliage Remarks
Buds Vigor
Belle Heller H V D
Besse Howells H V D
Cheer H V D
Dave's Pink L+ V D
Elie H V
Holden H V D
King Tut O V S+
Pink Dawn L+ V D
Pink Cameo H A S+
Pink Flair H V D
Pinnacle L+ V S+
Prize H V S+
Rocket H V D
Romeo L V+ S-
Sham's Pink O A S+
Spring Glory H V S+
Spring Parade H+ V D
The General L+ V S+
B-46R L+ A+ S (a clean red)
Area 3
Flower Plant Foliage Remarks
Buds Vigor
adenopodum H V D
Album Novum O S S-
America L+ A+ S-
Amphion H A S
Anah Kruschke L V D
Ann Glass O A S+ sprawling
Annie Dalton H A- S+
Antoon van Welie L A S
A. Bedford L+ A S
Arthur J. Ivens L A- S-
Atrier O A S
Atrier x Atrier L V D foliage burn
Atroflo L+ V D beautiful foliage
Bagshot Ruby L- A S
Beau Brummel H A S
Betty Wormald dead
Black Beauty L A S
Blue Bird L V D
Blue Diamond L S S
Blue Ensign H V D
Blue Peter L+ V S+
Blue Tit L A D
Bonfire L+ V S+
Boule de Neige H A D cut back-old plant
Bowbells L+ A S
Brandywine H V D
Brookville L+ V S+
C x C4 L V D
campylocarpum O S S
Carex H A- S
Carita O V D young plant
carolinianum x pink mucronulatum H V S
Catawbiense Album H V S gangly old plant
catawbiense x metternichii O V D young: no indumentum
catawbiense rubrum x Elizabeth L+ A+ D
Cathaem H A D
chapmanii O V D young plant
Charles Dickens H A+ S
Chesapeake H V D
Clementine LeMaire L A S+
Conestoga L + A S
Confection H V D
Corona L A S+
Cowslip L- S D partly dead
Cunninghamii L V D
Cunningham's White L A D
Cynthia L A S
Dawn's Delight O S S+
Decatros Pink O A S+ young-gangly
Delaware H V D
Delicatissim O V D young
Devonshire Cream O S S
Dexter NYBG #5 L V+ D
Dexter NYBG #6 L+ A S+
Dexter 23 L+ V S
Dexter 121 L+ V S
Dexter 12A L A- S+
Dexter HSI L+ V S
Dr. H. C. Dresselhuys H V D
Dr. V. H. Rutgers L+ A S
Earl of Athlone L A- S
Elizabeth L+ A S+
Elizabeth x B. & A. #3 L+ A D
Essex Scarlet x Disca O V D young
Eureka Maid L+ A S
Everett Miller L+ V D
Everett A-6 (Dexter) H+ V S-
F. D. Godman L A S
Floribundum L- V S+ young
Fowle #19 (Dexter) H A S+
Fowle #20 (Dexter) L A S+
Galloper Light (azaleodendron) L A S
George Frazer O V D young
Gladys L A S bloomed last year
Gloxineum H A S
Goethe O A+ D
Goldsworth Yellow L+ A- S+
Gomer Waterer H V D
Handsworth Scarlet O V D cut back old plant, just growing out
Henrietta Sargent H A+ S+
Hockessin H V D
Humming Bird H A+ S+
Ignatius Sargent L A+ S
IW 54 H A S-
Jacksonii L- A D
Jan Dekens L A- S
Jean Marie de Montague H V S+
J. H. van Nes L A S
Flower Plant Foliage Remarks
Buds Vigor
Jock L A S+
keiskei H A+ D
Kettledrum H A S
Koster's Cream L A D
Lady Bligh L- A- S
Lady Gray Egerton H A S
Lady Eleanor Cathcart O V D young
Lady Longman H V S+
Lady Primrose O S S
Langley Park H A S+
Lee's Dark Purple H V D
Leona L- A+ S +
Loderi King George L A+ S
Louisa P. DeLand (Dexter) L+ V S
Louis Pasteur L A S
Madame Ida Rubenstein L A- S
Madam Masson L V D
makinoi (?) (No tag) L A D
Mars H A- S+
Mayday O V D
Maximum Rubrum L V D young
Michael Waterer H S D
Midsummer H V D
Montchanin H V D
Morris #3 (Dexter) L+ S S
Moses L+ A S+
Mosely BP#51-4 (Dexter) H+ A+ S+
Mrs. A. T. de la Mare O A S cut back old plant
Mrs. Betty Robertson L- A S+
Mrs. Charles Pearson O A S
Mrs. Furnival L- A- S
Mrs. G. W. Leak L V D
Mrs. 1. C. Williams L A+ S+
Mrs. Lionel de Rothschild H A+ S
Mrs. Mary Ashley L A S
Mrs. P. D. Williams L A- S-
Mrs. R. S. Holford L A D
Mrs. W. R. Coe O A S
mucronulatum H V deciduous
Naomi O A- S
Pale Mauve (Dexter) H A- S
P.J.M. H V D
Praecox L+ A- S
President Lincoln L A S
Prince Camille de Rohan L- V D
Princess Juliana L A- S+
pubescens x keiski H V S
Purple Splendour L+ A+ S+
Purpureum Grandiflorum L+ V D
Flower Plant Foliage Remarks
Buds Vigor
Queen Mary L- A+ S+
racemosum L+ V S+ bloomed heavily last summer
racemosum x carolinianum H V S
racemosum x keiski H V D large leaves for type
Racil H S S
Ramapo O A- S poor site next to path
Red Cloud L V S+ young
Red Start O V S+ young
Roberte O A S
Robins #2 O A+ S young
Robins #3 O V D young
Robins #4 O V D young
Robins #11 L+ V D young
Robins # 12 O V D young
Robins # 14 L+ V S+ young
Robins #16 H V S+ young
Romany Chal L+ A S+
Rosa Mundi H V D yellowish foliage
Roseum Elegans H V D
russatum H A S foliage eaten by insects
Salvini L A- S
Sappho L A S 2 poor and 1 good specimen
Sargenti H A S
Scintillation (Dexter) H+ V S+
Simplicity L V D
Sir Charles Butler L V D
Sir James L+ A S
smirnowii L V D
Souvenir of W. C. Slocock L A D
Spring Parade O V D
Stoplight O S S Young
Swarthmore (Dexter) L + V+ D
Swarthmore 12499-6 L+ A S
Swarthmore 12499-7 H A S
Swarthmore 12499-8 H V S-
Swarthmore 12499-13 L A+ S
Sweet Simplicity H A+ S+
Tan (Dexter) L+ A S
Tom Everett H+ V D
Trilby L+ A+ D
Unknown Warrior O A- S
Van Weerden Poelman H A S+
Vulcan L+ A- S+
Westbury Phipps (Dexter) H A S
Wilbar O A- D
Windbeam H V S+
Wyanoki H V D
Winterthur, Pink B. (Dexter) L+ V S+
Winterthur, Pink Late (Dexter)
1-x-18 L+ A+ S
Winterthur, Red (Dexter) L V S
Zuyder Zee L S S+