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O-P

Species Rhododendron Descriptions By Name
 
oblongilobatum
oblongilobatum

Bright yellow flowers, leaves edged with hairs

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oblongilobatum
oblongilobatum

Bright yellow flowers, leaves edged with hairs

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R. oblongilobatum

Or maybe R. valentinianum var. oblongilobatum. Botanists have had a bit of confusion over this plant (it’s all about long glandular hairs and where they are or aren’t), but there’s no denying that it’s a cutie. Its bright yellow flowers and its diminutive glossy green leaves are a real plus. A willowy growth habit that responds to pinching makes it a good rock garden candidate.

R. oblongilobatum is a member of Subsection Boothia and therefore tends to be epiphytic. This plant needs perfect drainage. Think of it as an orchid. It makes a fine container plant or grow it in a hanging basket. Exact hardiness is unknown but probably protect it below 25°F.

 
occidentale
occidentale

a named clone -DDgold

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occidentale
occidentale

Some good fall color as well

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occidentale
occidentale

a named clone -DDgold

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R. occidentale

This is a PACIFIC COAST  NATIVE famous for its garden-filling sweet fragrance.  It appears from southern California up the coast almost to southern Washington.  Its flowers – late in the season -- are mostly white but can vary with shades of red, pink and yellow.  Leaves are a glossy green and turn yellow in the fall.  This is one of two deciduous azaleas in the Northwest (R. albiflorum is the other), ranking among the best American native azaleas.

R. occidentale may reach five feet in ten years and often has a willowy, free-flowing feel. It responds well to trimming, so you can keep it whatever size you like. The fragrance is truly outstanding, often filling the garden on a warm day.  It is not a difficult or fussy plant once established.  Our plants are grown from various seed sources – some collected in the wild, others from deliberate crosses of selected cultivars.

As with all rhodies, make sure it has good drainage in a moist, loose soil.  It is quite sun tolerant and does not like dense shade. Rhododendrons are not heavy feeders, so give R. occidentale small amounts of fertilizer on Valentine’s Day and Mother’s Day. It is hardy here in its home on the Pacific Coast. 

ochraceum
ochraceum

a red that calls across the garden

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ochraceum
ochraceum

New growth with a touch of pink

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ochraceum
ochraceum

a red that calls across the garden

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R. ochraceum

Only introduced to the West in 1995, this species is proving to be a winner. It blooms easily, and the flowers are an intense rich red with nectar pouches deep in the center.  The foliage keeps its frosted look year round, and the indumentum on the underside of the leaf blends nicely with upper side. Best of all, it seems to be fairly compact – four feet in ten years. 

R. ochraceum makes a well-rounded shrub. Because it blooms in March and April when it is still relatively cool, the flowers last for up to three weeks, The intensity of the red  is truly outstanding. The truss, while of moderate size, is a well rounded ball. Give it a mix of sun and shade.

It seems to be perfectly hardy here in Western Washington, even escaping damage in the killer winter of 2010.

 
 
oligocarpum
oligocarpum

Soft pink to rose flowers

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oligocarpum
oligocarpum

Soft pink to rose flowers

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R. oligocarpum

R. oligocarpum is a member of the Maculifera subsection, which means that it is has a great deal of hardiness down to 0℉. It forms a rounded shrub of modest size – say four feet in ten years. The leaves are rounded with slight hairs on the margin. Flowers open deep pink and then fade to white. The purple nectaries deep in the throat grab attention.

Peter Cox (a world renown rhododendron expert) rates R. oligocarpum as a “fine species with first rate foliage and flowers.” The plant will handle a fair amount of sun (which will help it stay compact) and does not want deep shade. Good drainage is never lost on a rhododendron.

 
orbiculare
orbiculare

Hanging pink bells

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orbicular
orbicular

leaves like lily pads

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orbiculare
orbiculare

Hanging pink bells

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R. orbiculare

Here’s a compact bush – if grown in a sunny location – with a nicely tiered effect.  The soft pink flowers hang as dainty bell-shaped blossoms, blooming April to May. The leaves have interesting overlapping “ears” where the petiole (leaf stem) joins the leaf.  We often call them lily pads. This is an unusual and much sought-after plant. 

It will like partial sun, especially if you want to keep it compact. It may reach four feet in ten years and is hardy to 0° F.

 
oreotrephes
oreotrephes

Vibrant pink

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oreotrephes
oreotrephes

How's that for blue foliage?

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oreotrephes
oreotrephes

Vibrant pink

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R. oreotrephes

R. oreotrephes has the best of both worlds – honest flowers and great foliage!  Bright soft pink flowers are open faced and held in a dainty array that doesn’t pretend to be a massive truss.  The foliage has a blue cast to it that makes it a winner the entire year.  Best of all, its modest size helps it fit into today’s smaller gardens - say five feet in ten years.

R. oreotrephes  generally has an open, graceful habit that offers a tidy but informal feel with some of the coolest blue foliage in the genus.  This is a “good-doer” that adds distinction to the woodland garden. It is hardy to 0° F.

 
pachysanthum
pachysanthum

White with blotch, sometimes pink

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pachysanthum leaf
pachysanthum leaf

All kinds of tomentum year round -that's not mildew in the background - just contrasting tomentum

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pachysanthum
pachysanthum

White with blotch, sometimes pink

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R. pachysanthum

If you want the best of the rhododendron world, this plant is a MUST!  A wonderfully behaved ball of foliage that stays clothed to the ground (if grown in the open), yet  over-whelms with shades of grays, blues, silvers, tans and greens and then shows a beautiful orangey indumentum on the undersides of the leaves. If that’s not enough, R.  pachysanthum adds a truss of beautifully held pink-to-white flowers. 

This is one of those rhododendrons that wants sun but doesn't want to be broiled. It should make a three foot or so ball in ten years as it is slow growing and is hardy to  -5° F. It's always on our Top 10 list.

 
pachytrichum
pachytrichum

A pink flowered pachytrichum on Wawushan, Sichuan

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pachytrichum
pachytrichum

A white flowered form

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pachytrichum
pachytrichum

A pink flowered pachytrichum on Wawushan, Sichuan

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R. pachytrichum

This rhododendron is about the hairs – leaves, stems, petiole, pedicel – all are covered with hair. But this is no hippie; it’s a regal plant that holds its leaves with elegance and produces flowers that range from white to pink, often with a purple blotch in the throat. The stems can often be a dark red and maintain their hairs for several years. It will form a rounded shrub about five feet high in ten years. It comes from Sichuan and is hardy to approximately -5° F.

 
pendulum
pendulum

Flowers singularly or in pairs

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pendulum
pendulum

Fuzzy, fuzzy, fuzzy

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pendulum
pendulum

Fiding a niche among hemlock root tangles

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pendulum
pendulum

Flowers singularly or in pairs

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R. pendulum

This is a very special dwarf that distinguishes itself with a superb collection of hairs – a dense wooly indumentum that covers the new growth and then persists on the underside of the leaf.  The flowers occur in twos or threes in cool creamy white as a casual comment on foliage that is not to be outdone.  It comes from eastern Nepal, southern Tibet and Bhutan.

R. pendulum requires excellent drainage and ample moisture – it’s an epiphyte in the wild.  Once established, it does very well in western Washington, enjoying a partially sunny location. It makes a fine container plant or try growing it in a hanging basket or on a stump. It's hardy to 10° Fahrenheit and may reach two feet tall in 10 years.

pentaphyllum
pentaphyllum

The edging varies but always adds interest

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pentaphyllum
pentaphyllum

A pink quinquefolium

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pentaphyllum
pentaphyllum

The edging varies but always adds interest

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R. pentaphyllum

If you are fond of R. quinquefolium, you will love her sister, R. pentaphyllum with the same reddish leaf margins, fall color, and slow-growing diminutive habit.  The flowers, however, are a flat rosy-pink. It’s especially good in a pretty container.

Even though small-leaved, this deciduous Japanese azalea prefers a bright spot with little exposure to direct sun.  It flowers in March in the Pacific NW and will show fall color in shades of yellow.  It’s hardy to approximately -5°F, -15°C.

 
 
phaeochrysum
phaeochrysum

As seen in Tibet, 1997

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phaeochrysum
phaeochrysum

As seen in Tibet, 1997

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R. phaeochrysum

R. phaeochrysum blooms in early mid-season and should grow to four feet or more in ten years. Often seen in Tibet, N. Yunnan and Sichuan as the dominant plant, it is not often seen here. Shiny dark green leaves that look like they have just been polished and this amazing truss of blooms are hard to beat. It's the commonest member of the Taliensia series and upholds the high standard of this group quite well.

R. phaeochrysum requires excellent drainage and likes to keep its roots cool but still needs some sun - morning is probably best. It's hardy to approximately -5° Fahrenheit.

 
pingianum
pingianum

A clear, pure pink

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pingianum
pingianum

Not a bad show

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pingianum
pingianum

A clear, pure pink

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R. pingianum

R. pingianum is a bit of a “sleeper.”  Its pure pink flowers without markings are not overly large, but their numbers in each truss makes the overall effect quite stunning when in bloom. The plant makes a rounded shrub and the indumentum on the underside of the leaves is the whitest of all species. It may reach five feet in ten years.

R. pingianum comes from central Sichuan, including the famous Emei Shan. It wants some sun but doesn’t want to be cooked. Morning sun is perfect. It needs consistent gentle watering and well-drained soil. Small amounts of fertilizer on Valentine’s Day and Mother’s Day keep it growing well. It's hardy to -5° F / -20° C.

 
pocophorum
pocophorum

A waxy red

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pocophorum
pocophorum

A clone named Cecil Nice

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pocophorum
pocophorum

A waxy red

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R. pocophorum

If you like thick, fleshy, glossy red flowers, this species rhododendron is for you. The large calyx is an added bonus, but I know that these flowers always bring extra “oh’s” and “ah’s.”

 

R.pocophorum‘s  leaves  are quite glossy, dark and shiny. The underside is covered with an orangish, wooly indumentum. It belongs to the Neriiflora Subsection, noted for its intense reds.

R. pocophorum tends to be an upright shrub reaching perhaps five feet in ten years. It requires excellent drainage and prefers a bright spot but protection from intense sun. North facing exposures are excellent. It comes from high altitudes in SE Tibet and NE Yunnan.

 
polylepis
polylepis

The flower color has a wide range bluish purple

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polylepis
polylepis

The flower color has a wide range bluish purple

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R. polylepsis

R. polylepis is a red-stemmed, scaly beauty from the Triflorum family. “Polylepis” means “with many scales.” It can be expected to grow to six feet in 10 years and to be hardy to 5° F or -15 C. You can prune it to the shape you desire.  It can make a nice screening plant if given sufficient sun. 

Rhododendron polylepis will appreciate a mix of sun and shade with protection from the hot afternoon sun. It needs  

small amounts of fertilizer on Valentine’s Day and

Mother’s Day along with gentle watering. A loose, well-aerated soil with good drainage aids the cause.

 
praestans
praestans

A large truss on a classy "big leaf"

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praestans
praestans

Next year's leaf buds

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praestans
praestans

A large truss on a classy "big leaf"

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R. praestans

R. praestans is another of the majestic big leaved rhodies that give a bold “tropical” look in the landscape.  This one has a shiny bronzy-brown plastered indumentum on the back of long rugulose leaves that taper at the base.  As the plant matures, the indumentum will become shiny gray-white to fawn.  The winged petiole is another detail that establishes  R. praestans’ identity. 

R. praestans  is the slowest growing of the “big leaves” and so will not take over the entire garden. It may reach five feet in ten years. It also is one of the hardiest, so it does well here in the Northwest.  It comes from a limited area at the corner of Yunnan, Sichuan and Burma. It is hardy to 0°F.

 
prattii
prattii

A fine white

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prattii
prattii

A fine white

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R. prattii

R. prattii is part of the Taliensia subsection of rhododen-drons, sister to R. bureavii and R. adenogynum.  The subsection is known for long-lived and slow-growing shrubs and small trees.  A.E. Pratt discovered prattii in E. Sichuan – hence the name.   Its polished leaves are covered with hair-like indumentum.  Its structure is open-growing. 

 

R. prattii is native to Sichuan, where it may grow to 10 feet over many years.  It may reach five feet in 10 years. It is hardy to -5° F.

 
protistum
protistum

What a truss

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protistum
protistum

What a truss

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R. protistum

Here’s Northwest Tropical at its finest! R. protistum has some of the largest leaves of any rhododendron.   The rugged leaf texture adds interest all year ‘round.  The maroon new growth  (that slowly turns to green) makes this plant truly stunning in the spring.  The leaves will ultimately develop a silver indumentum on the underside of the leaf. The red leaf bracts add even more interest.

Best if you grow it in a pot, as the early and lovely growth is subject to damage by frost and the plant itself will not survive a hard freeze.  Bring the pot into the garage on sub-freezing days and enjoy it on your deck or patio most of the year.

 
pruniflorum
pruniflorum

A real treat for the later bloom season

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pruniflorum
pruniflorum

Lovely red peeling bark

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pruniflorum
pruniflorum

A real treat for the later bloom season

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R. pruniflorum

This three foot midget packs a wallop. Exquisite little bells in a delicious purple hang down on long pedicels in multi-flowered clusters supported on trunks with peeling reddish brown bark. To add to the fun, the leaves have not one, but two kinds of scales: pale somewhat background scales that almost touch the more prominent brown scales. To top it off, the leaves are aromatic.

R. pruniflorum comes from Arunachal Pradesh (we didn’t see it on our 2017 trip to the Upper Sian Region), Upper Myanmar and SE Tibet. It blooms fairly late in the season. It will like more sun than shade, filtered is better than direct. Add small amounts of fertilizer on Valentine’s Day and Mother’s Day. Give it gentle watering. Don’t keep it soaked. It needs good drainage with a well-aerated soil. 

Seems hardy to 5°F

 
pseudochrysanthum
pseudochrysanthum

Pink or white it's still pseudochrysanthum

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pseudochrysanthum
pseudochrysanthum

Some forms have lovely blue foliage

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pseudochrysanthum
pseudochrysanthum

Pink or white it's still pseudochrysanthum

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R. pseudochrysanthum

R. pseudochrysanthum is quite variable in its homeland, Taiwan. Common to all forms are the unique, thick, leathery, pointed leaves.  The midrib on the lower leaf surface has a line of indumentum while the rest of the underside is usually bare and polished smooth. The leaves range in color from an olive green to green to fairly blue. Sometimes there are hints of silver frost. The plant can form a very compact mound that makes it wonderful for a small space or it can be a larger version that may reach five feet in ten years. 

R. pseudochrysanthum wants a  lot of sun, but you can overdo it, burning the foliage. The flowers usually start with pink buds and may stay pink or fade to white. It is hardy to a bone-chilling -10° F.