JARS v41n4 - Fall & Winter Foliage Color Of Rhododendrons & Azaleas

Fall & Winter Foliage Color Of Rhododendrons & Azaleas
Bob Badger
Kent, Washington
Text reprinted from "Seattle Rhododendronland", the Seattle Chapter newsletter

The enormous impact of rhododendrons on the planning and arrangement of gardens here and in Europe has been concentrated in the short time of just 50 or 60 years, since the tremendous collections of rhododendron species in Asia by Wilson, Forrest, Kingdon-Ward, J.F. Rock and others. The flood of new species gave rise to a secondary swarm of new hybrids which has continued unabated, until the present time.
The glorious floral display of rhododendrons fills our gardens from March until July with beauty and colors that literally defies description. Flowers bloom in shades of whites, pinks, reds, yellows, blues and purples. Flowers, individually from one quarter of an inch to nearly seven inches in diameter are borne singly or in many arrangements up to great trusses of twelve to fourteen inches in diameter. Evergreen leaves range in size from three-eighths inch long to two feet and more.
The garden importance of evergreen rhododendrons is one of solidarity out of bloom and riots of color tones when in bloom. To this I will agree. But, I wish to draw your attention to their fall and winter color not the color of flowers. I refer to the fall and winter color of their evergreen foliage. The most exotic of winter foliage color changes occurs among the Asian rhododendron species. Some fine color changes also occur in first and second generation hybrids thereof, but the species are the prizewinners.
Nearly all lepidote (scaly-leaved) rhododendrons change their leaf color after the first hard frosts of fall. Some changes are most vivid. The greens of summer are replaced by purple, bronzy-red and maroon tones for winter. Perhaps you never noticed this before.
Take heed of the following list so that you may plant the dwarf or "little people" sorts in elevated positions above walls or in rockeries. Then you will not have to kneel on the wet soil to appreciate their winter beauty. The medium, people-sized plants, should be planted on a more level area where you can shake hands with them in winter. Lastly the tallest growing sorts with the brilliant under leaf colors should always be sited uphill on slopes above the grass or path, or on the upper terrace so that the fine colors beneath their leaves can be more easily seen as you walk by on a winter's day.
One bright day in December almost on the Winter Solstice, I visited the Rhododendron Species Foundation Garden at Federal Way. With the kind assistance of the staff and President, I wandered through the magnificent Study Garden area of related species plants.
Here are my notes of seventy of the finest winter foliage colorations seen that day. I rated their winter color on the following basis:
(A)  Overall appearance of the winter leaf color.
(B)  Shining, glossy or matte look of the upper leaf.
(C)  Brilliance of the underleaf color tones whether the color comes from scales, hairs, wax or lack thereof.
(D)  Vividness of the color of this year's growth.
(E)  Color of the bark.
(F)  Bright color tones of the growth and flower buds.
(G)  Remarkable colors on the petioles of the leaf.

Rating Key:
WC - *** Absolutely choice, a must have for fall and winter gardens. A colorful plant in bloom or out, but an asset especially in the winter months. Plant in a place of honor.
WC - ** Above average leaf and other color changes, a winter attraction in anyone's garden.
WC - * Remarkable color changes in leaf upper surface. Also other attributes in color from stems, or under leaf or petioles or buds. Plants to see.
WC - 0 I passed it by and did not list it.

WC - *** R. zaleucum
An upright tall shrub that presents a superb winter color effect for landscaping uses. The bright walnut-brown stems bear many long very dark green leaves that flutter in the stronger winds, exposing their ghostly, glaucous-white under surfaces. As if that was not enough, the flower buds are covered with scales of a bright golden-yellow hue. A very choice selection for your garden.

WC - ** R. eximium
A small tree with oval leaves up to twelve inches long. The rugulose (rough surfaced) leaves are dark green ultimately but are often covered, as are the petioles and new shoots, for a year or more with a thick rusty cinnamon colored tomentum. Beneath, the leaves are covered with a thick indumentum of a rusty-orange color. A very attractive small tree that "shows off" its leaves all year long. Plant it in a more protected position, but where it can be seen.

WC - *** R. fulvum
A large shrub bearing darkest green leaves a little rolled on the edges. The midrib and veins above are pronounced lines of yellow-green against the dark green. Buds are furred in a soft orange tomentum. The plant usually holds its leaves somewhat upright, exposing the most vivid, vibrant orange indumentum in the genus. This is perhaps the most brilliantly indumented and finest of winter colored shrubs for the garden. Plant for everyone to see and for you to see from your own windows in the winter!

WC - *** R. rigidum
Another taller shrub whose finer forms are most attractive. The stems are a bright plum-purple color and are decorated with smallish blue-green leaves. The effect is very different - somewhat like R. oreotrephes , I feel this plant should be planted along an entry walk for fine winter color effect.

WC - *** R. sulfureum
An upright shrub with bright soft green leaves. It's very ornamental on a dull winter day because cupped in each terminal leaf cluster is a flower bud of a brilliant red color. The edge of each bud scale is traced with pure white. A choice plant to be placed where it can be easily viewed in the winter.

WC - *** R. 'Sir Charles Lemon'
This "honorary species" is a large upright shrub bearing dark green leaves covered beneath with a red-orange indumentum which is seen every time the wind blows. The new growth, the petioles and the buds are all of a rich maroon-red color. A striking plant if placed where it can be easily seen.

WC - ** R. beanianum
A low shrub with somewhat shining, oblong, very dark green leaves, somewhat crinkled on the edges. The leaf petioles and stems are a contrasting reddish color and are covered with bristly greeny-brown hairs. The reddish-brown woolly indumentum appears rich brown when the sun shines through and one sees the leaf from below.

WC - ** R. calostrotum
An upright twiggy shrub. Leaves of the first growth are a matte gray maroon above but they stand up exposing pinkish-tan color beneath. In contrast, the leaves of the second growth are a brilliant blue-green.

WC - ** R. campanulatum var. aeruginosum
A medium sized shrub that has blue toned green leaves re-curved at the edges. The indumentum beneath is of a soft reddish-yellow color. The petioles, buds and new growth are of a bright red color for contrast. Most attractive and colorful in winter.

WC - ** R. chamaeunum
A mounded shrub, more upright, covered with lustrous bright maroon-red leaves. Stems of new growth are the same bright maroon-red.

WC - ** R. cuneatum
A tall but looser growing shrub with gray-green leaves above that are dark fawn to darker rusty beneath. The bigger leaves are thinner in texture and when lighted by the sun and viewed from the other side, have an almost iridescent olive color that is quite interesting.

WC - ** R. fastigiatum
A tight mound with leaves of a gray-blue coloration with bright flashes of blue. Underleaf is a soft mushroom color.

WC - ** R. fictolacteum
This shapely well branched small tree is abundantly covered with large dark green leaves. The leaf petioles are usually a gray-buff in color, while the undersides are clothed in an orange-brown indumentum which is easily seen as you look up into the plant. To be placed and grown as a dominant small tree in your landscape. Hardy!

WC - ** R. hanceanum (and var. nanum )
The leaves are of a medium green occasionally brushed in bronzy tones. However, the buds and petioles are of a bright red-maroon color. Some forms are covered in leaves of bright maroon. Very attractive when well grown.

WC - ** R. hyperythrum
A low shrub with quilled, medium-green leaves with a thin-lined bright yellow midrib above. The petiole is red in contrast to the green leaves. The bud scales are also in shades of red and green. Altogether, the winter colors are intriguingly unusual, if not bizarre. It should be planted where it can be easily seen anytime visitors walk by.

WC - ** R. impeditum
A mound of gray-green leaf tones above, suffused here and there with light and medium blue colors - especially on the last growths of summer. Flower buds are tinted with fawn and maroon colors. Underleaf is pale grey-green.

WC - ** R. makinoi
A medium sized, rounded shrub with long, narrow, re-curved green leaves. The petioles are covered with a gray tomentum while the terminal buds are a soft brown. The total effect is very unusual, but pleasing.

WC - ** R. moupinense
A spreading lower growing shrub with bright yellow-green leaves. Each flower bud is a contrasting bright red-maroon.

WC - ** R. nivale subspecies nivale (old name was R. paludosum )
Larger cushions of soft olive-green colors above with contrasting bright red flower buds on the terminals. Underleaf is yellowish to fawn in color.

WC - ** R. orbiculare
A medium sized rounded shrub with medium green rounded leaves having "ears" which overlap the petiole from each side. The undersides are palest greeny-white. The petioles are of a pinkish-red color. The growth and flower buds are decorated with long pale yellow-green bracts which project upwards like clusters of fingers. A very pleasing plant to view in winter.

WC - ** R. oreotrephes
An upright growing shrub with decided glaucous blue-green almost round leaves. Some forms are semi-deciduous, but the best forms are not. These better forms have maroon to purple to violet stems which are very noticeable in the winter.

WC - ** R. polydadum (old name was R. scintillans )
A more upright grower covered with matte-green leaf tones, gray-brown beneath. Noticeable maroon colored flower buds are cupped in the terminals.

WC - ** R. racemosum
An upright twiggy shrub with medium green to grayish leaves with pink and gray flower buds. The outstanding feature on the best forms is that the last year's new growth stems are a bright attractive red.

WC - ** R. radicans
A creeping mat-former with glossy leaves of rich green tones, here and there changing to lustrous bronzy and maroon tones. The tiniest of the "little people".

WC - ** R. russatum
A taller, full shrub with aromatic leaves. Leaves are olive-green and darker with the growth points studded with soft maroon colored flower buds. Leaf undersurface is brownish-rusty in color. This year's growth stems are a distinct maroon color.

WC - ** R. sataense
This upright evergreen azalea inhabitant of volcanic peaks of Kyushu, sparkles with bright red, rusty-maroon and vivid yellow-green leaves, interspersed at random over the plant. A brilliant display of color in the winter garden.

WC - ** R. succothii
A medium sized shrub with blued-green oblong leaves that are distinctly "eared" (cordate) leaves. The leaf petioles are so short that the leaves cluster on the branch ends, an unusual effect.

WC - ** R. telmateium (old name was R. idoneum )
A low shrub with leaves somber matte gray-green above but with golden colors beneath. The new growth stems are also a rich golden color in contrast to the leaves. Very striking winter effect.

WC - * R. arizelum
Another shapely, small tree which is hardy. Large, obovate dark green rough surfaced leaves clothe the plant. The petioles and new shoots are coated with a grayed cinnamon colored indumentum. The leaf undersides are clothed with a rich cinnamon brown indumentum. A tree in the landscape.

WC - * R. baileyi
A scraggy, upright shrub with leaves of gray-green or gray russet colors. Not that attractive except that every flower bud is of an unusual pinkish color that contrasts with the leaves.

WC - * R. brachycarpum
A medium sized, rounded shrub with larger dark green somewhat re-curved leaves. The midrib, petiole, and buds are of a distinct yellow color which contrasts vividly with the dark leaves. A pleasing garden effect.

WC - * R. bureavii
A medium sized full shrub with dark green leaves, somewhat shining above as the tomentum falls away. The leaves nestle tightly against the shoots, seldom exposing the beautiful thick, woolly rust colored indumentum beneath.

WC - * R. calophytum
A stout-branched very hardy tree bearing long narrow leaves up to fifteen inches long. The medium green leaves are paler green below. In some forms the leaf petioles are of a reddened tone while in others they are of the same green as the leaves. The winter garden effect is that of a powerful massive, dominating evergreen tree.

WC - * R. campanulatum
A larger shrub, somewhat loose in habit with larger oval leaves of a medium green with purple petioles and new growth stems. Leaves of larger plants frequently flutter in the winter wind exposing their brownish-red felted undersides.

WC - * R. campylogynum
The various forms are rich dark green in leaf color with the more exposed leaves brushed a maroon color. Petioles are often bright yellow-green.

WC - * R. crassum
A big shrub which is the hardiest of the large-flowered Maddeniis. The crisp veined leaves are of an olive-green color above. But when caught by the wind the undersides are of a shining greenish-gold color.

WC - * R. dasypetalum
Bronze tones above, over greens with buff colors on the underleaf.

WC - * R. dauricum
The type is a twiggy upright shrub whose leaves are russety-bronze all over above and coppery-buff below (the leaves of the white flowered form never color in winter). They remain a bright yellow-green as do the buds. A dwarfer sort of regular color, has leaves that turn a rich russety color all over.

WC - * R. davidsonianum
A taller upright shrub with medium green leaves and green-gold buds. The better forms have red stems.

WC - * R. falconeri
A fairly large, stout branched tree bearing rather large rough-surfaced very dark green leaves. The midribs above are of a bright contrasting yellow color. The leaf is covered below with a dense indumentum which is of a rusty-orange color. Very striking in larger plants. It is somewhat tender and should be placed in a protected area but situated to be easily seen for its winter effect.

WC - * R. fargesii
A large shrub which on the richer colored flower forms has thicker elliptic leaves with rather a reddish-purple petiole borne on stems reddened toward the tips. A noticeable effect in winter.

WC - * R. flavidum var. flavidum (old name was R. flavidum )
A rather erect and taller growing shrub with somewhat glossy medium green leaves. Pink flower buds rest on the upright terminals. Underleaf surface is grayed-green in color.

WC - * R. hippophaeoides var. hippophaeoides (old name was R. hippophaeoides )
An erect and spreading shrub with matte leaves of a distinct grayed green-blue color. Buds are variable in maroon and reddish colors. The underleaf is a brighter yellowish-buff color often seen if the wind flutters the leaves. Stems of the new growth are of a fawnish-yellow color.

WC - * R. imperator
Another shrublet of green and bronzy leaves, edged deeper maroon as are the petioles.

WC - * R. insigne
A medium shrub having the same garden effect as R. brachycarpum , that is to say, green leaves with yellow midribs and petioles. In one form the leaf also has a yellow edge. The indumentum beneath has a coppery-pink color when viewed from the side or below.

WC - * R. intricatum
A compact, tangled and intricately branched shrub whose leaves are various shades of yellowish-green to olive tones above. Underleaf is buff to straw colored.

WC - * R. kaempferi
A tall evergreen azalea species whose leaves are of various shades of maroon, green and orange-red. It has buds covered with rather red bud scales.

WC - * R. keiskei
The tall upright forms have long yellow-green and bronzy leaves with pale maroon buds. The lower mounding forms are smothered in rich maroon leaves that are green beneath. The buds are of the same maroon tone. Var. cordifolia is the spreading prostrate form from elevations nearly a mile high. Its leaves are of maroon, yellow and green tones while the buds are similar.

WC - * R. keleticum
A vigorous low cushion of a shrub with outer branches almost creeping. The small leaves turn a burnished, shining dark purple maroon with greener leaves interspersed. The bright maroon-red petioles are very noticeable.

WC - * R. lepidostylum
A spreading, low shrub of compact habit whose leaves, the most brilliant blue of the genus in summer, turn to duller shades of gray-green and maroon in the winter.

WC - * R. leucaspis
A low bushy shrub that has matte-green furry leaves set with buds of pinkish-red.

WC - * R. linearifolium
This upright evergreen azalea species or variety has long narrow dimorphic leaves in the winter, resembling lacy purple fluffs on the branch tips. Very unusual effect.

WC - * R. mallotum
A stout branched, medium sized shrub bearing stiff, oval, dark green rumpled leaves with a bright yellow midrib above. The leaf petioles, new growth stems, and buds are clothed with a tight greenish gray indumentum. Beneath, the leaves are covered with a rich orangey-brown indumentum.

WC - * R. nakaharai
This evergreen species is the prostrate carpeter of the azaleas. Its narrow leaves are crisp light blue-green with bronzy flashes. The leaves are covered above with long white hairs while the buds are clothed in hairs of brightest gold.

WC - * R. nivale subspecies boreale (old names were R. violaceum and R. stictophyllum )
Larger cushions of soft matte gray-green colors overlaid with grayed-maroon shades. Leaves rufous colored beneath.

WC - * R. patulum
This shrublet has leaves of maroon-red tones that are soft gray-green below. The bud scales are of a brighter red hue.

WC - * R. pemakoense
A low, spreading mounder covered with dark green leaves above. Very striking in winter, because every flower bud is colored a bright red.

WC - * R. prostratum
An almost prostrate shrublet with shining bright green leaves. Flushed bronzy on some leaves and with orange-red young stems.

WC - * R. pseudochrysanthum
The dwarfer forms have somewhat pointed leaves held up at an angle. The medium green leaves are often covered with white meal like tomentum. The growth shoots, petioles, flower and growth buds are red or maroon colored. The leaves are frequently red or maroon underneath. The effect is somewhat artificial but striking.

WC - * R. recurvoides
A low compact shrub with somewhat narrow dark green leaves that are shining above. The young shoots are a dark maroon color and like the leaf petioles, are covered with olive-brown bristles. The indumentum beneath is thick and spongy and of a rich olive tone which contrasts with the bare yellow-white midrib. Plant it on the up slope above a walk.

WC - * R. rupicola var. chryseum (old name was R. rupicola )
A low mound of variable tones ranging from darker olive-green tones to richer bronzy highlights. Flower buds are rather pink in color. Under surface of the leaves are fawn to rust in coloration.

WC - * R. serpyllifolium
Another evergreen azalea with a wide spreading flat habit, smothered in tiny one-half inch leaves of a rich maroon color.

WC - * R. spinuliferum
A sprawling, larger shrub with long leaves of a green fuzzy-matte appearance. The three inch or so long leaves are almost always edged around with a richer maroon color.

WC - * R. tsariense
A smaller rounded shrub with a woolly fawn colored indumentum often persisting on top of the last leaves of the new growth. The smallish obovate leaves are of a medium green color. The stems, petioles and buds are of a golden-yellow tone that hints of orange in certain lights. A plant to be seen by all.

WC - * R. williamsianum
A low spreading shrub with smaller rounded, dark green leaves that are a light greeny-white below. The winter buds are a bright red-maroon in contrast to the leaves.

WC - * R. yakuinsulare
An evergreen azalea best described as a low mounder. The tiny, narrow leaves are of a bright, somewhat shining bronzy color. Very restrained in feeling.

WC - * R. yakushimanum
A low, compact, mounded shrub with dark green re-curved leaves with a yellow-green midrib. The petioles and buds are covered with a soft white or gray tomentum. At times a white tomentum remains on the uppermost leaves of the growth, adding to the character of the plant.

Bob Badger, District 2 Director, is a long time fan of rhododendrons and azaleas at all seasons of the year. With his wife, Marge, Bob operates a nursery and display garden at Kent, Washington.

Ed Bancroft, a member of the Seattle Chapter photography group, combined his photos with Bob's commentary for a Seattle Chapter program on foliage color. This article is based on that program.