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Species In Our Midst
Rhododendron auriculatum

by Joe Bruso

Rhododendron auriculatum
Picture by S & J Perkins
Rhododendron auriculatum in Federal Way, WA

Rhododendron auriculatum

Rhododendron auriculatum is the sole species assigned to subsection Auriculata, which falls under subgenus Hymenanthes, section Ponticum. This section contains the species commonly referred to as elepidotes or more generally, broad-leaved evergreen rhododendrons lacking scales. R. auriculatum's closest relatives are found in subsection Fortunea, which contains species such as R. fortunei and R. decorum. The specific name auriculatum means eared, referring to the earlobe (auriculate) shape of the leaf where it joins the petiole. It is native to several provinces in China (Hupei, Sichuan, Guizhou), being found from low to mid-altitudes (1,600-7500 feet or 500-2300 m) where it grows in woods, on high ridges and on rocky slopes of forests. R. auriculatum was discovered by Augustine Henry in 1885 in Hupei province. It was first introduced into the west by Wilson in 1901, and subsequently reintroduced by him in 1907 and by others in subsequent years, with the most recent re-introduction being in 1980. R. auriculatum is rated hardy to -5°F (-20°C) by Greer and others.

Rhododendron auriculatum forms an upright, spreading, tree-like plant, growing up to 33 feet (10 m) high in the wild, and half that in cultivation. It can reach 6 feet (2 m) in 10 years. Leaves are long (up to 12 inches or 30 cm) and narrow to broadly narrow, tending to stand out horizontally. The upper sides are dull dark green and slightly hairy. The undersides are paler green with whitish or brown hairs. The stems of new growth display long, red, ribbon-like bracts. Flower buds are large, conical and tapered, the outer bud scales having long tips (called perulae) extending beyond the bud, similar to R. maximum and a few other species. Vegetative buds are similarly shaped. The scented flowers are showy, funnel-shaped, to 4 inches (10 cm) wide, in fairly loose trusses of 6-15, appearing as late as August. Flower shape and size has been compared to those of Easter lilies. Color ranges from white to rose-pink, with a green basal patch.

Since Rhododendron auriculatum flowers and develops new leaves in the heat of the summer, it is best planted in a shaded area to avoid causing the flowers to wilt prematurely and to prevent damage to the new foliage. For the same reason, it appreciates ample watering during this period of new growth. The lateness of the new growth is thought to make this species potentially vulnerable to damage in areas that experience early fall frosts, as this new growth may not yet be hardened off. The experience of some growers contradicts this, however.

Rhododendron auriculatum has been much used in hybridizing. As one would expect, many of these hybrids are late blooming and/or fragrant. Unfortunately for us in New England, many if not most of the crosses have been made with tender species by West Coast and English hybridizers, and the resulting hybrids, while much admired in those places, are probably not hardy in most of our region. A few names that may be familiar include 'Polar Bear', 'Argosy', 'Burgundy Rose', 'Bustard', 'Clotted Cream', 'Flare' and 'Iceberg'. The Greigs of Royston Nurseries on Vancouver Island produced a series of late-flowering R. auriculatum hybrids including 'Royston Reverie', 'Royston Rose' and 'Royston Festival'. Again, they are too tender except in protected areas of our coastal regions. However, there are some hybrids with at least 1/4 R. auriculatum parentage that are hardy in most of New England. Examples include 'Atlantis' (-20°F or -30°C), 'Summer Snow' (-15°F or -25°C), 'Summer Solace' (-15°F or -25°C) and 'Summer Summit' (-20°F or -30°C). Members of the "Summer" series inherit hardiness from their R. maximum parent.

Rhododendron auriculatum has a unique combination of characteristics such that once you have grown it, you will not easily mistake it for another species. The combination of the long, conical buds with perulae, the lateness with which it blooms and puts out new growth, the auriculate shape to the base of the leaves, stickiness of new growth, leaves held horizontally, and the large fragrant flowers distinguish this species from all others. It gets quite large with age, and is generally best appreciated once it has attained significant size after 20 years or more of growth.

Like most species, Rhododendron auriculatum cannot normally be obtained at your local nursery. However, seed is often available from sources such as the ARS Seed Exchange, the Rhododendron Species Foundation (RSF) and local growers. The RSF has offered plants for sale lately rating it "quite easy" to grow. There has been chatter lately on the rhododendron e-group regarding a pink form of R. auriculatum that originated with the Greigs, who used it as a parent in their hybridizing program in the 1930's (see above). Plants propagated from cuttings of this form have been/will be made available by the RSF.

Several Massachusetts Chapter members, mostly living near the coast in zones 6 and 7, are successfully growing this species and report it to be healthy. However, one local grower found the deer find it so irresistible, he had to build a cage around it for protection. I'm growing one small plant given to me by a fellow chapter member. It spent last winter in a coldframe. This past summer, its first year in the landscape, I was ready to send it to the compost pile, as the old leaves looked droopy as if it were about to expire. To my surprise, the plant began pushing out new growth during the first half of August, and is now very healthy looking. This fall I lined out several plants started from seed in the fall of 2002. These seedlings have much narrower leaves than the older plant. New growth continued alarmingly late into the summer, in synch with its older brother. Time will tell if any of these plants will survive my Zone 5b/6a winters in Hopkinton, MA.

Joe Bruso, Hopkinton, MA

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