Wednesday, February 16, 2011

Scented Rhododendrons

Reprinted from The BC Council of Garden Clubs Bulletin, January/February 2011

Text and photos from Harold Fearing, Past President of Fraser South Rhododendron Society

One day as I was weeding in the greenhouse, I brushed against the foliage of a small plant and noticed a wonderful spicy fragrance. That got me to thinking. Fragrance is something we don’t normally pay much attention to in rhododendrons. Only a few of the normal lepidote or elepidote rhododendrons have fragrant flowers, unlike azaleas, many of which are quite fragrant.

Of the regular hardy rhododendrons, R. fortunei is probably the best-known fragrant species. It is usually a vigorous, large growing plant with pale pink flowers. The fragrance is subtle, not something you notice across the garden, but still nice when you are near the plant. Others of the Fortunea subsection, such as R. decorum and R. diaprepes have similar fragrances.

Probably the most fragrant regular rhododendron we have in our garden in one distributed in the lower mainland as R. rigidum ‘Bodineri’. This plant originated from the late Frank Dorsey, a long-time rhodophile. While I don’t remember all the details of the story he told, the ‘Bodineri’ part was a name he apparently coined. The plant keys out to R. rigidum, and appears identical to two other clones of R. rigidum I have, except for the fragrance. And this is fragrance you can smell across the garden, especially on a sunny warm day. The plant covers itself with blooms as well, so it is a spectacular plant for the garden.

There are also several relatively tender rhododendrons, which are supposed to have large and very fragrant flowers: R. madenii, R. nuttallii, R. dalhousiae, and R. edgeworthii. I have no personal experience with these, as they are all too tender for the exposed garden we have. I think some people in more protected gardens in the lower mainland are able to grow R. edgeworthii successfully however.

Among the deciduous species there is more choice. One of my favourites is R. atlanticum. This is a smaller plant with grey green leaves. It spreads by stolons and so eventually becomes a spreading bush with lots of stems. The flowers have a long tube with flaring petals at the end and a sweet fragrance powerful enough to smell from some feet away.

R. luteum is another very fragrant plant. It is a deciduous azalea, bright yellow and a native of the Caucasus area of eastern Europe. Many of the fragrant hybrid azaleas have R. luteum in their parentage. Our own west coast azalea R. occidentale can also be very fragrant, as are several of the east coast native azaleas, such as R. viscosum.

I have seen the claim in several places in the literature that most fragrant rhododendrons are white or pale pink. The theory is that the fragrance attracts pollinators and so there is no need for flashy colours.

R. luteum is obviously a glaring exception to this claim. Although many of the others are pale coloured, I don’t really know how strong the scientific evidence for that claim is.

photo by Harold Fearing
But enough of flowers and back to what got me thinking about fragrance in the first place. The plant I was weeding was R. ledebourii, considered a variety of R. dauricum by some. Simply sweeping your hands through the foliage is enough to release a sweet spicy fragrance. The related species R. sichotense, and R. dauricum itself, have similarly fragrant foliage. This characteristic is also inherited by some of the dauricum hybrids, eg., the well-known ‘PJM’. R. ledebourii is a native of Siberia, so is completely hardy, and is also one of the earliest to bloom, even in late January or early February.

Several other small leaved species share a similar fragrant foliage, for example, R. sargentianum, and its selected form ‘Maricee’, and the similarly flowered R. primuliflorum. Among the somewhat larger-leaved plants, the foliage of R. cinnabarinum, with its attractive blue green foliage, is supposed to have a distinctive spicy smell when crushed. However, I could not detect this, at least not on a cold November afternoon, in any of the several clones I have, except for R. xanthocodon, which is now considered a subspecies of R. cinnabarinum. Again according to the books, R. hippophaeoides is another common species with fragrant foliage. A narrow leaved version, var. occidentale, which I recently acquired, does seem to be fragrant, but the more common wider-leaved clone ‘Haba Shan’ has no smell that I could detect.

So while fragrance of either flowers or foliage would probably not be the primary reason for choosing a particular plant, it is another dimension to our enjoyment of rhododendrons. And, at this time of year, when you are crawling around on hands and knees weeding, a few plants with fragrant foliage can certainly make the task more bearable.

photo by Harold Fearing
The small-leaved R. ledebourii, R. dauricum album, and R. sichotense, all have aromatic leaves whose spicy sweet fragrance wafts up when the leaves are brushed or when the sun warms them.

R. xanthecodon is a member of the cinnabarinum family, whose lovely blue-green leaves have a bracing resinous odour if rubbed or crushed.

Geographic distribution of Rhododendrons & Azaleas


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