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Species Rhododendrons Descriptions By Name
R. adenogynum

Here is a modest gem that might reach four feet in ten years. It has distinctive leathery leaves that have a spongy indumentum that is yellow to olive brown in color. The flowers are soft pink to white. The plant tends to bloom at a young age and makes a compact specimen that looks good year around.

R. adenogynum is native to SE Tibet, Yunnan and Sichuan and is a member of Subsection Taliensia, a branch of the rhododendron family noted for its outstanding plant habits — mostly compact, with spongy indumentum.

This rhododendron will like well-aerated soil with good drainage, filtered sun and gentle watering, very small amounts of fertilizer on Valentine’s Day and Mother’s Day. It’s hardy for western Washington.

R. ambiguum

R. ambiguum is one of those willowy Subsection Triflora plants noted for its compact habit and its hardiness. The willowy growth and fragrant leaves, as well as its ability to take the sun, make this an ideal plant for an appealing low screen. Easily pruned back, it may reach four to five feet in ten years, or you can keep it smaller. The pale yellow flowers, two to seven on a stalk, will delight you.

This rhododendron will like more sun than shade and small amounts of fertilizer on Valentine’s Day and Mother’s Day. Consistent watering helps, good drainage is a must. It’s hardy to -5°F, -21°C.

R. amundsenianum

Here’s a brand new rhododendron from southern Sichuan in China. It will probably be placed in Subsection Lapponica. This is the largest grouping of lepidotes (plants with scales), most of which are dwarfs with small leaves. This one seems to bloom easily. The blue is a real winner, glowing warmly and intensely.

Being an alpine, this rhododendron will like a bright spot but not a hot spot. It wants good drainage with consistent gentle watering and small amounts of fertilizer on Valentine’s Day and Mothers’ Day. We are guessing that it will reach four feet in ten years. It seems to respond to pinching by sending out multiple stems, so a judicious pinch of the new growth will yield a bushier shrub, keeping it from getting leggy. Being an alpine, it has been hardy here in the Pacific Northwest so far, and we expect that to continue.

R. arboreum

R. arboreum is a regal rhododendron which adds a distinctive touch of class to your garden. It has polished gold, silver or rust colored plastered indumentum on its dark, shiny green leaves depending on the form. The flowers may be red, pink, or white. 

Our R. arboreum plants have grown to fifteen feet in 30 years. Some have bloomed pink/red, some pink/white, some red, some white. All have attracted birds seeking sturdy limbs upon which to build their nests.


R. arboreum will like: filtered sun, small amounts of fertilizer on Valentine’s Day and Mothers Day, gentle watering.

R. argipeplum

This is a truly bristly fellow with lots of interest. Argipeplum means “with a white covering” and the leathery leaves have a thin white or tawny, wooly indumentum on the underside. What’s more, the new growth has lots of bristles which give this plant a distinct character.

The flowers are a strong red that come early in the season.

R. argipeplum is closley related to R. barbatum. Like R. barbatum, R. argipeplum will develop a smooth polished reddish trunk with age. It may grow to five feet in ten years.

R. argipeplum would appreciate small amounts of fertilizer on Valentine’s day and Mother’s Day, gentle watering that keeps it moist, and good drainage with well-aerated soil.

R. argryophyllum ssp. hypoglaucum

What a mouthful of a name for a sweet rounded ball of beautifully polished foliage! The flowers are a soft pink to white and the new growth is an amazing bronze. The underside of the leaves has a shiny silvery smooth indumentum. Native to China, the plant does well here in the Northwest, making a six foot ball in ten years.

R. argyrophyllum var. hypoglaucum will do well in a fair amount of sun, allowing it to remain a ball. In shade it will be more open. It tends to bloom from a young age in mid to late spring.

This plant will like: small amounts of fertilizer on Valentine’s Day and Mother’s Day, gentle watering and well-aerated soil with good drainage.

argyrophyllum ssp. hypoglaucum
R. arizelum

R. arizelum is a fine foliage plant with superb thick cinnamon indumentum on the underside of the leaf! The flowers open pale yellow then fade to pink and finish white! At times it looks like there three different colors on the same plant. This is a distinctive plant of noble bearing. It’s somewhat slow-growing and tends to branch fairly readily. Its bark will develop shades of pink and reddish brown.

If grown in the shade it may grow to six feet in ten years. Brighter spots will allow for a more compact plant.

This rhododendron will like partial shade. It would love a woodland canopy. Provide small amounts of fertilizer on Valentine’s Day and Mother’s Day, gentle watering, well-aerated soil with good drainage and avoid a very windy spot.

R. asterochnoum

R. asterochnoum is closely related to R. calophytum. Both have characteristic long leaves and ultimately form small trees in 30 or 40 years. R. asterochnoum adds indumentum to the underside of the leaf, although this seems to vary somewhat from population to population. The foliage is sturdy and rugose. We saw large stands of it at Black Bamboo in Sichuan, where the indumentum was indeed somewhat variable even on one mountain.

Here’s what makes R. asterochnoum asterochnoum, hairs on the mid-rib and veins. This indumentum on the back of the leaves is diagnostic, but variable. Lots of fun for the botanist in you.

Plant in dappled sun to a more open exposure. Fertilize lightly on Valentine’s Day and Mother’s Day. Keep it well watered just like any other rhododendron. It will reach five to six feet in ten years. It is hardy to 0°F.

R. augustinii

This old favorite lights up your garden with masses of blue flowers in mid-spring, followed by willowy new growth in bronzy gold and red. It is easy to grow and wants a fair amount of sun. It grows quickly and blooms at an early age. It may reach six feet in ten years but is easily kept smaller.

R. augustinii is part of the Triflora subsection, a group of plants noted for their narrow pointed leaves. R. augustinii has a furry mid-rib on the back of the leaf!

It prefers an open location that is bright but it doesn’t like the hot afternoon sun. Plant in light, well- drained soil, and give it small amounts of fertilizer on Valentine’s Day and Mother’s Day. Consistent gentle watering is best. It is hardy to approximately 0° F.

R. augustinii ssp. chasmanthum

This form of R.augustinii blooms a bit later than most augustiniis but rewards with softer shades of blue that make this plant a stunner. Very free flowering. The new growth is outlined in red on yellow green, but then the whole leaf turns to green as it ages. It comes from Yunnan, SE Tibet and western Sichuan.

R. augustinii ssp. chasmanthum is an easy plant to grow. Give it a fair amount of sun (but don’t put it in a hot spot), and it will bloom heavily after just a few years. Its willowy growth habit is a contrast to many more formal rhodies.

It will like small amounts of fertilizer on Valentine’s Day and Mother’s Day. Give it gentle watering. Plant in well-aerated (no clay or other tight) soil with good drainage.

It is hardy to approximately 0°F or -17°C.

augustinii chasmanthum
R. auriculatum

A wonderful species, R. auriculatum deserves a place in your garden because it blooms late (July-August) and its funnel-shaped white-to-light-pink flowers are deliciously fragrant!

It eventually forms an upright spreading tree, but it is more likely to reach about six feet in ten years. The new growth shows off lovely long, red ribbon-like bracts and the narrow green leaves are hairy!

R. auriculatum’s forebears live in China, in wooded high ridges and forest slopes. It was introduced to the west in 1901 and, although not easy to find, has endeared itself to gardeners and collectors alike.

This rhododendron will like shade and filtered sun, small amounts of fertilizer on Valentine’s Day and Mother’s Day, gentle and ample watering especially in its summertime period of new growth and flowering, well drained and aerated soil. It’s hardy to -5°F and is also fairly heat tolerant.

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