Rhododendrons and azaleas
To locate images associated with this article please visit our
image collection at Country, Farm and Garden Photo Library
Rhododendron is a large genus of at least 800 species. It ranges over most of
the Northern Hemisphere, with just a few Southern Hemisphere representatives.
Species exist in all climates from the tropics to the alpine, or arctic, zones.
The wider family to which they belong, the Ericacae,
is distributed worldwide and includes many fine garden specimens such as Erica, Calluna, Pieris, Leucothe, Kalmia
and Pernettya.
Rhododendrons can truly be said to have
it all — colour, form and foliage — and in a bewildering variety. They range
from minute plants scarcely a couple of centimetres high right through to
forest giants; they are available in almost every flower colour and often
combine their colours in the most striking and unusual ways; and their foliage
covers the entire range from less than a centimetre to some of the largest
leaves of any shrubs. They display such a variety of colour, size, foliage and
style that they offer something for almost every garden and gardener.
Nomenclature
You will notice that this chapter is
headed rhododendrons and azaleas, butt they are really one and the same thing —
all azaleas are rhododendrons. Deciduous and evergreen azaleas are as much
rhododendrons as any of the large-leafed evergreen shrubby types. This comes as
a surprise to many gardeners, but a close examination of the flowers and
general structure of the plants will reveal the truth.
Cultivation
Rhododendrons are undemanding plants that
present no great difficulties for most gardeners. Growing them largely comes
down to understanding the soil conditions they prefer and choosing the
appropriate plants for your conditions.
Soil
All the plants of the Ericacae have very fine, hair-like,
roots. They do not send down long tap roots capable of mining the subsoil nor
do they have heavy aggressive surface roots that can plunder the topsoil. This
root system enables rhododendrons to make the best use of the shallow soils in
which many naturally grow, but in periods of drought the fine roots dry out
quickly and if they become waterlogged, they rot. Also, they can’t penetrate
heavy soil. This may make them seem fussy plants but it all comes down to one
thing, HUMUS.
To grow good rhododendrons you should
make the utmost effort to condition your soil before planting. It is virtually impossible to work in too much compost or other humus
containing material. Apart from insect damage or sunburn nearly all
rhododendron disorders can be traced back to some problem with the roots and
ultimately the soil.
Many rhododendrons have evolved to grow
under deciduous trees where they receive an annual dressing of fallen leaves
and where the soil, over time, becomes composed almost entirely of leaf mould.
This type of soil is not high in nutrients but it is extremely high in humus
and is moisture-retentive yet well drained. It is not a deep soil; and even if
it were the tree roots would remove many of the nutrients from the lower
levels. However, the soil that is there is loose and easily penetrated by fine
roots, water and air. This sort of compost-based soil is usually acidic.
To get the best from your rhododendrons,
you need to try to recreate these conditions in your garden. Start by working
plenty of humus-rich compost into the soil; leaf mould and garden compost are
ideal and the black thatch that you find under the surface layer of fallen pine
needles is also very good. You could also add bark chips and very well rotted
sawdust; these don’t contain much humus but they will open up the soil and
improve the effectiveness of your compost. When the soil has a loose, fluffy
texture, a light dressing of acid plant fertiliser can be added and you are
ready to plant.
Hardiness
Rhododendrons come from a wide range of climates and this is reflected in their wide range of hardiness. Tropical species tolerate only very short, light frosts while the hardiest species can withstand temperatures of -25°C or lower, which is extremely hardy for a broad-leafed evergreen. Most of the common garden rhododendrons are capable of withstanding -5– -15°C, which makes them suitable for most temperate climate gardens. Some of the fragrant species and cultivars are slightly frost tender in southern districts but they may be grown if given light winter protection. Although the plants are largely hardy, it is important to note that the flowers are not. Very early flowering rhododendrons are always prone to having their flowers destroyed by frosts.
Shade
Rhododendrons are generally thought of as
plants for shade and it is true that most of them do prefer to be sheltered
from the hottest sun. However, there are varying degrees of shade, and
rhododendrons tend to prefer quite bright positions in light or dappled shade.
Too shady and they will have difficulty forming flower buds and will become
lank and leggy growers. The ideal position for large leafed rhododendrons is a
fairly open position under deciduous trees.
Deciduous azaleas, alpine rhododendrons
and smaller leafed forms prefer brighter sites and many will perform well in
sunny positions. As a rule, the larger the leaf the
more shade it will requires, but when in doubt err on the brighter side,
because, provided the soil conditions are good, most rhododendrons will
tolerate some sun.
Mulching and nutrition
Mulching with compost or material such as
rotted pine bark in spring and autumn will help to conserve moisture as well as
insulating the surface roots from climatic extremes such as hot sun and ground
freezing cold. Avoid mounding excessive mulch up against the trunk or main
stems of larger rhododendrons, it may cause a deterioration
in the bark and lead to fungal or viral troubles.
Rhododendrons do not need to be heavily
fed, mulching will often provide some enough supplementary nutrients, but even
under the best of conditions, plants may occasionally suffer from nutrient
deficiencies. When feeding rhododendrons it is best to use mild fertilisers;
too strong and you’ll burn the surface roots causing a browning of the leaf
tips and edges. It is generally best to use mild organic fertilisers such as
liquid blood and bone or sulphate-based (acidic) chemical fertilisers. These
will ensure that the soil is not excessively ‘sweetened’, that is made too
alkaline. Incorporating some slow release fertiliser granules or a mild acid
fertiliser in with the twice yearly mulching will usually maintain adequate
nutrient levels.
When deficiencies do occur, the most
common are a lack of nitrogen, iron or magnesium. Lack of nitrogen leads to
slow growth and an overall yellowing of the foliage that affects the old growth
first. Nitrogen is most effectively added by using urea, but this is a very
strong chemical so use it at no more than 2 g per 5 litres of water or
severe, sometimes fatal, burning of the roots may result. Milder sources of
nitrogen include ammonium sulphate and ammonium nitrate. Make sure these
fertilisers are thoroughly watered in.
Magnesium deficiency sometimes appears as
an ‘autumnal’ look, with reddening foliage and falling leaves. But as a rule,
lack of magnesium or iron is usually indicated by chlorosis, which is a
yellowing of the leaf with distinctly green veins. This may be due to
deficiencies in these elements (more likely in container grown plants) or to
excess alkalinity, which prevents the plant from making the best use of the
available nutrients. It’s difficult to tell the cause of chlorosis so aim to
cover all possible causes. Good sources of iron include iron sulphate or
chelated iron, while the most common source of magnesium is Epsom salts
(magnesium sulphate). Mix about 20 g each of iron sulphate and magnesium
sulphate in 5 litres of water. Thoroughly soak the soil around the plants with
this mixture. The sulphate base of these fertilisers will help to neutralise
any excess alkalinity. Chelated iron is the fastest-acting source of iron but
is expensive and requires more care in its application.
Container Growing
Their dense root system makes
rhododendrons, particularly evergreen azaleas, ideally suited to container
growing. Specimens not exceeding about 1.2 m high and wide after 10 year’s
growth are ideal.
By using a good quality potting mix
(garden centres often have special rhododendron potting mix that is slightly
more acidic than the standard mix) and regular applications of liquid blood and
bone or other mild fertilisers, the plants should be to remain in the container
for up to two years before repotting is necessary.
When the time to repot does arrive you
have a choice. You can either move the plant up to a larger container or
undertake some light root pruning and repot it in the same container. If you
don’t remove more than a third of the roots, you won’t need to cut the foliage
back, although it is a good opportunity to trim the plant if necessary.
Compatibility
Rhododendrons look magnificent by
themselves or they can be mixed with other shrubs. Their soil and site
requirements make them natural companions for camellias, fuchsias and many
woodland perennials, and it is when grown with such plants that they look their
best.
Because rhododendrons have such fine
roots they are unlikely to damage or weaken any surrounding plants. Indeed, the
opposite is more likely to be true so be careful when
placing very vigorous perennials, such as Acanthus,
near rhododendrons.
Pests and diseases
Leaf roller caterpillars and thrips are
the most common pests. Leaf rollers are usually restricted to small-leafed
rhododendrons and evergreen azaleas but thrips may attack any of the forms. As
both of these pests can be hard to get at, systemic insecticides usually give
the best results.
The main fungal diseases are azalea leaf
gall and mildew. Azalea leaf gall causes a very unsightly thickening and
distorting of the new growth. The damaged leaf turns white as the fungal spores
mature but eventually it blackens and dries. Fungicides will control the spread
of the disease and you should also remove damaged leaves before they fall.
Mildew is most common in the autumn and most fungicides are effective against
mildew.
Die back and root-rot diseases, such as Armillaria, Phomopsis and Phytophthora
rots often cause problems with rhododendrons and are usually an indication that
the drainage is poor. There is very little you can do to control these
problems, as once a plant shows signs of damage it is often too late to save
it. Check your growing conditions to prevent a recurrence.
Pruning and trimming
Rhododendrons seldom need regular
pruning, just occasional trimming. Any trimming and shaping is best done
immediately after flowering because this leaves the whole growing season for
regrowth and limits the effect of pruning on the following season’s flowering.
Unless you want the plants to set seed
you should remove the spent flower heads. This ‘dead-heading’ allows the plant
to concentrate its energies on growth rather than seed production. It is often
also a good idea to pinch out the apical leaf-bud when dead-heading as this
encourages strong lateral branching and dense growth.
In most cases a very light trimming back
and shaping is all the pruning that will be required. Dead or spindly branches
should be removed and the ventilation of a large bush will be improved if some
of the centre growth is removed. Heavier pruning should be done with care
because many rhododendrons are reluctant to reshoot from bare wood. Always cut
back to a whorl of leaves because that is where the most vigorous buds are
located.
Very old, overgrown plants can be cut
back to stumps. It is best if you can leave some foliage on the stump, but even
when cut back to bare wood a well-established plant will generally eventually
reshoot. It can take several years before the plant resumes normal flowering
and further shaping is almost certain to be required as it grows.
Propagation
Rhododendron species are often propagated
by seed, but cultivars and selected forms must be propagated vegetatively.
Cuttings are the most widely used method and layering is also popular. Some
rhododendrons strike poorly from cuttings and these varieties used to be
grafted, and often still are, but many are now being propagated by tissue
culture.
Seed
Sow your seed on a finely sieved 50/50
mixture of sphagnum moss and potting mix. No pre-sowing treatment is required.
Do not cover the seed, just sow it on the surface and keep it lightly shaded
and moist. The seed usually germinates best at around 18°C. The young seedlings
are small and slow growing and to achieve the best results they really must be
grown under controlled conditions. Seedlings do best with high humidity, even
warmth (around 18°C) and occasional dilute liquid feeding. The seedlings can be
potted on once they have formed their first true leaves although they may still
be too small to handle conveniently at this stage. No harm will come to them if
they are left until easier to handle provided their nutrient requirements are
met. Growing rhododendrons from seed is not difficult but there may be a
considerable waiting period before you see any flowers.
Cuttings
The methods vary slightly depending on
the type of plant. For evergreen azaleas and small-leafed rhododendrons, use
softwood cuttings or semi-ripe cuttings of the new spring growth; these strike
quickly but may be difficult to keep turgid. For large-leaf rhododendrons
(leaves over 20 mm long), use semi-ripe cuttings, which may be taken from
about mid December through to mid May; early cuttings may strike before winter but
later cuttings will probably not get under way before the following spring.
Deciduous azaleas can be difficult to grow from cuttings; try 75–110 mm
long soft to semi-ripe cuttings from mid to late spring.
Rhododendron species and cultivars
All of the species and cultivars listed
here are hardy to at least -10°C and flower mid-season (late September to early
November) and are evergreen unless otherwise noted.
Species
The following are some of the more
popular or influential species.
R. arboreum (northern India to southern China)
An early-flowering upright small tree
with medium-sized deep olive green leaves. It has bright red campanulate
flowers in rounded trusses of 15–20 blooms. There are several forms including
‘Album’ (white) and ‘Roseum’ (deep pink) and it is a parent of many
early-flowering red cultivars. 2.5 m × 1.8 m.
R. catawbiense (Eastern United States)
A large bush with medium to large, glossy, deep green, oval leaves. It has white, pink or mauve flowers in trusses of up to 20 blooms. It is an important species that has frequently been used to add hardiness and heavy flowering characteristics to cultivars. 2 m × 1.8 m.
R. ciliatum (eastern Himalayan region)
A small compact bush with glossy,
rounded, bronze green leaves fringed with fine hairs, and widely flared white
flushed pink flowers in loose clusters of up to 4 blooms. It often blooms early
and has reddish-brown peeling bark that is very distinctive. 1 m ×
1.2 m.
R. cinnabarinum (eastern Himalayan region)
A large upright bush
with striking reddish brown peeling bark and aromatic bright to bronze green,
medium-sized, glossy leaves. The waxy tubular
flowers are deep brownish-red and are carried in clusters of up to 5 blooms.
2 m × 1.5 m
R. edgeworthii (eastern Himalayas, southern China & Burma)
A small bush with a rather open growth
habit and medium-sized, elliptical, dark green leaves with a heavy indumentum
on the undersides. The white flushed pink flowers are fragrant and are carried
in loose clusters of about 3 blooms. This species, which is the parent of many
fragrant hybrids, is hardy to only -8°C. 1.2 m × 1.2 m.
R. forrestii (Tibet, southern China & Burma)
A low, spreading bush with slightly
bullate, rounded, deep green, glossy leaves. The waxy bright red flowers are
carried singly or in pairs. 30 cm × 75 cm.
R. fortunei. (eastern China)
A large bush or small tree with oval mid
green leaves up to 200 mm long. The large, fragrant, pale pink flowers
fade to white and are carried in trusses of up to 7 blooms. This species has
everything — impressive foliage, masses of fragrant flowers, great hardiness
and vigour. 2.5 m × 2 m.
R. griersonianum (southern China & Burma)
A spreading bush that
has been extensively used in hybridising. The
narrow mid green leaves are up to 200 mm long with an indumentum and the
flared bright orange-red flowers are carried in loose trusses of about 5
blooms. 1 m × 1.5 m.
R. japonicum (Japan)
Formerly known as R. molle (and it may yet revert to that name), this deciduous azalea has hairy elliptical leaves and yellow to orange red flowers in trusses of up to 12 blooms. This
species, the ‘Mollis Azalea’, was very important in the development of many
cultivars. 1.8 m × 2 m.
R. kiusianum (Japan)
A densely twiggy evergreen azalea with
tiny oval leaves covered in fine hairs and small bright purple flowers in
clusters of up to 5 blooms. Mid season. This azalea
becomes deciduous when exposed to extreme cold. Several colour forms are
available, including white and pink. 60 cm × 1 m.
R. occidentale (western North America)
A large deciduous azalea that remains
compact for many years. It has elliptical to oblong leaves that colour
brilliantly in autumn and very fragrant white to cream flowers with pink and
yellow markings in trusses of up to 12 blooms. Several forms are available of
which the most common are ‘Equisita’ and ‘Delicatissima’. 1.5 m ×
1.5 m.
R. williamsianum (southern China)
A densely foliaged compact bush with very
distinctive bright green orbicular leaves up to 50mm long. 50m m
bell-shaped flowers in clusters of 2 or 3 blooms. The colour ranges from
light to deep pink. Mid season. 45 cm ×
60 cm. Often used in hybridising.
R. yakushimanum (Yakushima Island off southern Japan)
A small, densely foliaged, mounding bush
with very distinctive deep green, leathery leaves with rolled edges and a heavy
woolly white indumentum on the undersides. The white to pale pink flowers open
from deep pink buds and are carried in round trusses of up to 10 blooms. There
are many cultivated forms and hybrids and these are often called ‘yak’ hybrids.
60 cm × 1 m.
Vireya rhododendrons
The tropical vireya rhododendrons have
always enjoyed a fairly limited popularity as greenhouse or frost-free garden
plants. Although tending to be rather straggly plants they often have fragrant
or very brightly coloured flowers. They are not seasonal and may flower at any
time, with autumn the most common.
Vireyas are not difficult to grow
provided they are protected from frost. If you live in a mild frost-free
climate you can treat vireyas much like any other rhododendron, otherwise an
unheated greenhouse is usually all the protection required.
Among the more common vireya species are R. aurigeranum (bright orange-yellow); R. jasminiflorum (honeysuckle-like,
tubular, very fragrant, white); R.
javanicum (yellow to light orange); R.
laetum (soft yellow to orange); R.
lochae (bright red); and R. zoelleri
(golden-yellow edged bright orange).
Cultivars
The following are just a few of the
thousands of cultivars available. The parentage and breeding date are given
because they are valuable clues to the nature of a plant. As you grow more
rhododendrons and learn more of their history you will be surprised at just how
much information can be gleaned from a phrase such as “a griersonianum hybrid raised in 1939.”
Dwarf bushes, less than 1 m high
‘Brickdust’ (R. williamsianum × ‘Dido’ 1959)
Rounded bright green leaves and campanulate pinkish orange flowers.
‘Curlew’ (R. ludlowii × R. fletcheranum 1969)
Small, oval, bronze green leaves and wide open bright yellow flowers that often appear early.
‘Elisabeth Hobbie’ (‘Essex Scarlet’ × R. forrestii var. repens 1945)
Oblong very deep reddish-green leaves and blood red campanulate flowers.
‘Ginny Gee’ (R. keiskei × R. racemosum 1979)
Small rounded leaves with very bright green new growth; masses of tiny pink and white flowers.
‘Patty Bee’ (R. keiskei ‘Yaku Fairy’ × R. fletcheranum 1978)
Small elliptical leaves and soft yellow flowers in early spring.
‘Scarlet Wonder’ (‘Essex Scarlet’ × R. forrestii
var. repens 1960)
Deep green oblong leaves and small
trusses of intense red bell-shaped flowers.
‘Snow Lady’ (R.
leucapsis × R. ciliatum 1955)
Mid green, slightly
hairy, rounded leaves and very slightly fragrant pure white flowers in loose
trusses in early spring.
Medium sized bushes, 1 m to 1.8 m high
‘Blue Diamond’ (‘Intrifast’ × R. augustinii 1935)
Oblong deep green to
slightly glaucous leaves with wide open lavender to mid blue flowers in small
clusters.
‘Bumble Bee’ (R.
ponticum hybrid)
Narrow deep green
leaves and conical trusses of purple flowers with a very dark blotch.
‘Christmas Cheer’ (R. caucasicum
hybrid)
Rounded mid green leaves and small
trusses of pale pink and white flowers that open from deep pink buds in late
winter or very early spring.
‘Jingle Bells’ (‘Fabia’ × ‘Ole Olson’ 1974)
A densely foliaged bush
with mid green leaves and loose clusters of orange flowers that fade to golden
yellow.
‘Lem’s Cameo’ (‘Dido’ × ‘Anna’ 1962)
Oblong, deep bronze green leaves and
reddish new growth; waxy apricot-pink flowers with lighter tones in trusses of
up to 20 blooms.
‘Nancy Evans’ (‘Hotei’ × ‘Lem’s Cameo’ 1983)
Deep bronze green,
leathery, oblong leaves and reddish new growth; bright
golden-yellow-edged-orange flowers opening from orange buds in trusses of up to
20 blooms.
‘Percy Wiseman’ (R.
yakushimanum × ‘Fabia Tangerine’ selfed 1971)
Deep green slightly
glossy leaves; cream flowers with pink edges and yellow markings in trusses of
up to 15 blooms.
‘Rubicon’ (‘Noyo Chief’ × ‘Kilimanjaro’ 1979)
Deep green, slightly bullate, oblong
leaves; waxy deep blood red flowers in trusses of up to 18 flowers.
‘Unique’ (R.
campylocarpum hybrid 1934)
Mid green, leathery, oblong leaves on a
densely foliaged, neat, mounding bush; dome-shaped trusses open light pink from
deep pink buds and fade to cream.
‘Virginia Richards’ ([R.
wardii × ‘F.C. Puddle’] × ‘Mrs Betty Robertson’ 1966)
Oblong mid green glossy leaves; pink buds
open to orange-cream flowers with pink and yellow tones in trusses of up to 12
blooms.
‘Winsome’ (‘Hummingbird’ × R. griersonianum 1930)
Mid green lanceolate
leaves and masses of deep cerise flowers in loose clusters.
‘Yellow Petticoats’ (‘Hotei’ × [‘Pink Petticoats’ × R. wardii] 1983)
Mid green oblong leaves; bright yellow
slightly frilly flowers in trusses of up to 15 blooms.
Large bushes, over 1.8 m high
‘Anna-Rose Whitney’ (R.
griersonianum × ‘Countess of Derby’ 1954)
Large, mid green, oblong leaves up to
200mm long; clear deep pink flowers in rounded trusses of up to 12 blooms in
late spring; 3 m × 3 m.
‘Cornubia’ (R.
arboreum × ‘Shilsonii’ before 1912)
Light to mid green oblong leaves; bright
clear red flowers in rounded trusses in very early spring; one of the most
widely planted early red cultivars; 3 m × 2 m.
‘Fastuosum Flore Pleno’ (R. catawbiense × R. ponticum
before 1846)
Large light to mid green oblong leaves;
light purple semi-double flowers with yellowish throat markings and purple
spotting; the first of the still very few double flower rhododendron cultivars;
3 m × 2.5 m.
‘Fragrantissimum’ (R.
edgeworthii × R. formosum 1868)
An open, loosely structured bush with
deep bronze green, slightly hairy, elliptical to lanceolate leaves; very
fragrant, large, white-flushed-pink trumpet-shaped flowers in loose clusters; a
slightly tender, often untidy bush but its fragrance keeps it popular and it
espaliers well; 2 m × 2.5 m.
‘Lem’s Monarch’ (‘Anna’ × ‘Marinus Koster’ 1971)
Large mid green oblong leaves; pale pink
or white flowers with deep pink edges in very large conical trusses of up to 20
blooms; ‘Point Defiance’ is from the same cross and is very similar in all
respects. Both are superb plants. 2.5 m × 2 m.
‘Loderi King George’ (R.
griffithianum × R. fortunei 1901)
Slightly glaucous oblong leaves up to
200mm long; mildly fragrant pale pink flowers open from deep pink buds; One of
a group of very similar, very impressive hybrids that will eventually grow to
tree-like proportions. 3 m × 3 m.
‘Mrs G.W. Leak’ (‘Coombe Royal’ × ‘Chevalier Felix de
Sauvage’ before 1934)
Medium-sized mid green leaves with very
sticky new growth; light pink flowers with conspicuous darker throat blotches
in trusses of up to 12 blooms. 2.5 m × 2 m.
‘Pink Pearl’ (‘George Hardy’ × ‘Broughtonii’ 1897)
Mid green oblong leaves; light pink
flowers with reddish spotting in large conical trusses open from deep pink buds
and fade to very pale pink. 3 m × 2 m.
‘Purple Splendour’ (R.
ponticum hybrid before 1900)
Deep green leaves that
are quite narrow and lanceolate; deep purple flowers with a very dark blotch in
rounded trusses. 2 m × 1.8 m.
‘Sappho’ (unknown before 1847)
Deep green lanceolate leaves; white
flowers with a striking blackish-purple blotch in conical trusses of up to 12
blooms; inclined to be leggy but easily shaped if kept trimmed when young.
2 m × 1.8 m.
‘Trude Webster’ (‘Countess of Derby’ selfed 1961)
Mid green oblong leaves up to 175mm long;
clear mid pink flowers in large conical trusses; a very impressive plant even
when not in flower. 2 m × 2 m.
‘Van Nes Sensation’ (‘Sir Charles Butler’ × ‘Halopeanum’)
Large mid green oblong leaves; mildly
fragrant, waxy, light pink flowers with soft yellow tones in large trusses.
2 m × 1.8 m.
Evergreen azaleas
Evergreen azaleas are very heavy
flowering and are often massed to provide solid blocks of colour. They show
more variety in their flower forms than other rhododendrons.,
with flowers that may be single, semi-double or double. Many of them are hose
in hose, a form in which the sepals develop into petals, thereby creating
another row of petals.
Although the largest of them may grow to
over 2 m high and wide, they are usually small plants around 1m × 1m or
less. They are divided into groups based on their parentage and understanding
these groups is the key to success with evergreen azaleas. The main groups are:
Indica
Derived from Rhododendron simsii, which is only hardy to about -4°C so it is not
surprising that this group includes some slightly frost-tender hybrids. Most
grow to about 75 cm × 1 m. Among the most widely available are
‘Albert Elizabeth’ (white edged deep pink, semi-double); ‘Bride’s Bouquet’
(white, double); ‘Comptesse de Kerchove’ (soft orange-pink, double; ‘Elsa
Kaerger’ (brick red, semi-double); ‘Goyet’ (bright red, double); ‘Leopold
Astrid’ (white edged red, double); ‘Little Girl’ (soft pink); ‘Mme. Alfred
Sander (deep pink, double); ‘Red Wings’ (pinkish red, single); ‘Ripples’ (deep
pink, double); ‘Rosa Belton’ (white edged mauve, single); and ‘Southern Aurora’
(white suffused orange, double).
Kurume
Kurumes are dense, compact growers with
small leaves and masses of small flowers early in the season. With great age
they can become large plants but may be kept trimmed to about 1 m ×
1 m if necessary. Most are hardy to about -12°C. Common cultivars include
‘Christmas Cheer’ (vivid cerise, single to hose in hose); ‘Hino Crimson’ (light
red, single); ‘Kirin’ (mid pink, hose in hose); ‘Kocho No Mai’ (purple,
single); and ‘Ward’s Ruby’ (deep red, single)
Kaempferi
This group includes the hardiest hybrids.
However, when exposed to very low temperatures they will drop most of their
foliage. Kaempferis vary in size but most are ultimately around 1.5 m ×
1.5 m. Widely available cultivars include ‘Elsie Lee’ (lavender, double),
‘Johanna’ (bright red, single to semi-double); ‘Lorna’ (mid pink, hose in hose
double); ‘Purple Splendor’ (purple, frilled hose in hose); and ‘Vuyk’s Scarlet’
(bright red, single).
Satsuki
Satsukis are usually less than 1 m
high and are hardy to about -12°C. They have large single flowers with highly
variable colouration. The very dwarf Gumpo Satsukis are often used as rockery
plants. Satsukis are not always easy to find but many nurseries stock
‘Benigasa’ (brick red, single); ‘Fuji No Tsuki’ (lavender, single); ‘Gumpo’
(various colours, single); ‘Hitoya No Haru’ (pink to lavender, single); and
‘Shiko’ (light purple, single)
Inter-Group
This is a catch-all group that include
hybrids produced by breeding between the other groups and also includes those
raised from newly introduced species. Among the best are ‘Ben Morrison’ (white
striped red, single); ‘Betty Ann Voss’ (light pink, single to semi-double);
‘Frosted Orange’ (orange with a white centre, single); ‘Happy Days’ (mid
purple, double); ‘Miss Suzie’ (bright red, single); ‘Sweetheart Supreme’ (light
pink, double); and ‘Tenino’ (purple, single).
Deciduous azaleas
Deciduous azaleas offer flowers in vivid
yellow and orange shades that are not often seen among the other rhododendrons
and many also develop bright red autumn foliage. Deciduous azaleas are divided
into groups based on their parentage but these have less significance to
gardeners than those of the evergreen azalea groups. Almost all deciduous
azaleas have slightly hairy leaves, are very hardy, bloom heavily from mid
October and grow to be 1.8 m × 1.8 m bushes.
Many nurseries are reluctant to stock a
wide range of deciduous azaleas because they tend to only sell during the
flowering season. Nevertheless, you should be able to find ‘Anthony Koster’
(yellow with an orange blotch); ‘Carmen’ (yellow flushed pink flowers with deep
gold throat markings); ‘Cecile’ (red with bright yellow markings); ‘Gibraltar’
(intense orange red); ‘Ilam Gold’ (yellow shaded and marked orange); ‘Ilam
Yellow Giant’ (golden yellow); ‘Melford Flame’ (vivid orange red); ‘Ming’
(orange with yellow markings); and ‘Red Rag’ (bright orange red to red).
Copyright Geoff Bryant
|
