Fragrant rhododendrons
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It is no surprise that rhododendrons are
among the pre-eminent garden shrubs because they have it all: magnificent
foliage (usually evergreen), neat shape and superb flowers — some of which are
scented.
If the fragrant rhododendrons have a
failing it is the restricted colour range of their flowers. Most have white to
pale pink blooms, and generally the more intense the colour, the less intense
the fragrance. This probably reflects the fact that brightly coloured flowers
have little need to use fragrance to attract pollinators and conversely
fragrant flowers do not need colour.
Most of the readily available scented
rhododendrons fall into one of three main categories. First is R. edgeworthii and its hybrids; second,
the species (and their hybrids) belonging to the Maddenia subsection of the
genus Rhododendron; and third, the
hybrids of R. griffithianum and R. fortunei.
There are a few other fragrant species
but they are not often seen. Also, many of the azaleas, especially the
deciduous azaleas, are fragrant, as are some of the vireya rhododendrons such
as those with R. jasminiflora in
their parentage. However, I’d like to concentrate here on the plants most
gardeners regard as “true rhododendrons”.
The first group is by far the most common.
Indeed the chances are that if you come across a relatively small (less than
1.8 m high) rhododendron with large white flowers that are flushed deep pink and heavily scented, it will be a R. edgeworthii hybrid.
Rhododendron
edgeworthii occurs naturally in North East Burma,
South East Tibet, Northern India and Southern China at an altitude of around 2000–4000 m. While this may seem a
very high altitude to New
Zealand gardeners,
certainly in the alpine range, the plants rarely experience hard frosts. Consequently
R. edgeworthii is only able to
withstand the occasional -8°C freeze and even lighter frosts can be very
damaging, especially to flower buds and new leaves, if unseasonable.
It is a stocky though rather open bush
and can reach 1.8 m high with great age. The pointed elliptical leaves
8–15 cm long, deep green, somewhat puckered with a dense covering of felty
hairs (indumentum) on the undersides. The funnel-shaped, scented flowers are
white, flushed with pink and up to 11 cm long.
Most of the R. edgeworthii cultivars were introduced from 1860 to 1890.
Although they tend to share the characteristics of the species and to be
similar to one another, none has the luxuriant indumentum of the species. Those
you are most likely to find in your local nurseries are:
‘Countess Of Sefton’ (1877). An open yet densely branched bush that loses most of its
foliage in cold winter areas. Its white flowers, usually carried in 2s or 3s,
open from pink buds. Around 1.5 m high.
‘Fragrantissimum’ (1868). This
is the most well-known of the fragrant rhododendrons, probably because its name
is so effective at promoting its scent. Unfortunately it tends to be a rather
untidy plant best suited to growing as an espalier unless severely trimmed each
year. Its large, pink-flushed white flowers have a strong, spicy fragrance.
Around 1.8 m high.
‘Princess Alice’ (1862). A neat
compact bush. Small clusters of large, strongly scented, white flowers with
longitudinal pink striping. Around 1 m high. This is the probably the best
cultivar for general garden use; it is neat, fairly hardy and flowers well.
‘Suave’ (1883). Well-grown
bushes are neat and compact, but plants suffering from poor drainage or frost
damage are untidy. The foliage has a light indumentum. White flowers, lightly
flushed with pink, carried in 2s or 3s. Around 1.2 m high.
None of these cultivars will withstand
regular air frosts of more than about -8°C. However, you may also see the New Zealand cultivar ‘September Snow’, which resulted from crossing R. edgeworthii
with the much hardier R. leucapsis. It is hardy down to about -12°C
and is a very compact bush with fragrant white flowers in trusses of 4–6
blooms.
The second group, those from the Maddenia
subsection, are larger shrubs — usually in the 1.8–3 m high range. They
are often called maddenii rhododendrons, after the species that gives the group
its name.
Most of the fragrant maddeniis
have very large, waxy, white, funnel-shaped flowers that resemble those of the
Christmas lily (Lilium regale).
Others, such as the pale yellow R.
johnstoneanum and the bright yellow R.
burmanicum, show variations in flower size and colour, but they tend to be
rather lacking in fragrance.
Among the fragrant species R. nuttallii and R. lindleyii, along with their selected forms and cultivars are
without peer. Their magnificent flowers that would be well worth cultivating
even if they didn’t have their spicy, nutmeg scent. Unfortunately these species
lack hardiness and tend to be damaged at air temperatures below -5°C.
There are many cultivars of this group.
Although most resemble the species, a few of the more distinctive cultivars are
worth noting.
‘Countess of Haddington’ (R. ciliatum × R. dalhousiae 1862). This
is a neat, compact, 1.2 m high bush with 15 cm long, deep green,
pointed oval leaves. Its funnel-shaped flowers are white to pale pink, flushed
and edged deep pink. The degree of fragrance varies markedly with the season:
some years there is little or no scent, other years it is extremely strong.
‘Else Frye’ (R. ciliicalyx × unknown 1963). Though a
neat bush when young it can become open with age. Beautiful and very fragrant,
pink-flushed cream, yellow-throated flowers in loose trusses of 3–6 blooms. It
grows to around 1.8 m high and can be espaliered.
‘Floral Dance’ (R. nuttallii x R. edgeworthii 1982). Considering its parentage you may think that
this cultivar would bridge the gap between the Maddenia and Edgeworthia
subsections. To an extent it does, though it is very much in Maddenia camp. The
large flowers, carried in groups of four, are white-flushed-pink to pale pink,
and the deep green, oval leaves have a tan indumentum. It is a rather open bush
that grows to around 1.5 m high.
All of the rhododendrons mentioned so far
are somewhat frost tender and are often damaged at -8°C. There is, however, one
group of hybrids, the R. griffithianum ×
R. fortunei cultivars, that combines hardiness with fragrance. Both the
parent species have very large leaves, huge conical trusses of fragrant white
to pale pink flowers and grow to be small trees. The hardiness of their
offspring comes from R. fortunei,
which withstands -25°C, R.
griffithianum being only a little more frost tolerant than the maddenii
rhododendrons.
While you’ll need plenty of space to
accommodate a collection of these 3 m+ beauties, most gardens should have
room for one or two. The only drawback is the viral disease that causes
ring-shaped purple markings on the foliage. This does not appear to cause any
great damage and most plants eventually grow out of it.
The first hybrids from these species were
the work of Sir Edmund Loder and were introduced about the turn of the century.
The same cross has been repeated several times since, most notably in the 1920s
& 30s by Lionel de Rothschild of Exbury fame, with similar results.
Until recently it was common practice
among British rhododendron breeders to give all the selected seedlings of a
cross a collective group or “grex” name as well as an individual cultivar name.
The first and best known of the R.
griffithianum × R. fortunei hybrids belong to the Loderi grex. The Angelo
and Naomi grexes are very similar plants. All are plants from the same or
closely related crosses but have slightly different characteristics. Cultivars
to consider include:
‘Angelo’ (1930). Very upright
trusses of white flowers open from pink buds.
Angelo ‘Solent Queen’ (1930). Very pale
pink with green spotting. Reasonably compact for this style — around 2 m
high.
‘Exbury Naomi’ (1926). Soft
pink with apricot and yellow tones. Less than 2.5 m high.
‘Irene Stead’ (before 1958). A
New Zealand-raised cultivar with bright pink flowers and narrow leaves.
Loderi ‘King George’ (1901). Pale pink flowers slowly aging to white with a hint of pink.
Loderi ‘Sir Joseph Hooker’ (1901). Mid pink flowers with darker veining.
Loderii ‘Venus’ (1901). Pure pale pink flowers. Probably the most fragrant of the Loderis.
‘Naomi’ (1926). Huge trusses of
pale pink flowers with yellow tones and light orange-brown throat markings.
Naomi ‘Nautilus’ (1926). The
flowers are deep pink over biscuit to orange tones with greenish throats —
bright for a fragrant rhododendron.
Next time you are in the nursery looking
for rhododendrons, ask about the scented species and cultivars. They are no
more difficult to cultivate than any other rhododendrons, and while you may
have to forgo some flower colour, giving up a little brightness is a small
price for the addition of an entirely different and altogether more luxuriant
sensation.
Copyright Geoff Bryant
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