|librarian2003 (librarian2003) wrote in weagardening,|
@ 2008-06-25 22:48:00
|Entry tags:||dwarf rhododendron, glendoick|
Week 10 - Plant of the week - Dwarf rhododenrons
For week 10, I was asked to look at Dwarf Rhododendrons as our plant of the week. Now, rhododendrons are a huge group, and even singling out dwarfs is still an enormous task. What to do? Well, I remembered the Glendoick Bird series, and so I have concentrated on those. I've added a few interlopers in as well - a handful of other birds not bred by the Coxes of Glendoick, and one Glendoick rhody that isn't named after a bird, but was bred by the founder of the gardens.
Here's the handout. It includes some useful addresses for more information:
GARDENING FOR PLEASURE
Plant of the week
Rhododendron : Dwarf rhododendrons in the Glendoick Bird series
Family : Ericaceae
Rhododendron is a name that comers from two Geek words, rodon, a rose, and dendron, a tree. There are more than 850 species, and 25,000 cultivars of evergreen and deciduous trees and shrubs in the genus, some of them epiphytic, from Europe, Asia, Australasia, and North America, but particularly from SW China, Tibet, Burma, N India and New Guinea. They grow in various habitats from dense forests to alpine tundra, and from sea level to high altitudes. They vary greatly in habit from prostrate shrubs to heights of 80 feet.
Rhododendron flower forms are:
Tubular; Tubular-bell-shaped; Tubular-funnel-shaped; Funnel shaped; Trumpet-shaped; Hose-in-hose; and Saucer-shaped.
Flowers are often marked with flares and spots inside, and encompass almost every flower colour. Some rhododendrons also have attractive young growth, from red to bronze or metallic blue. Some have decorative peeling bark.
Grow rhododendrons in moist but well-drained leafy, humus-rich, acid soil, (ideally pH 4.5 – 5.5). Shallow planting is essential: all rhododendrons are surface rooting and will not tolerate deep planting. Water plants during the summer if rainfall is less than 1 inch per week. Generally, they enjoy light dappled shade or part-day shade, but not early morning sun. They will tolerate a more open site if given shelter from cold, dry winds. Avoid frost pockets to reduce the risks of waterlogging and bark split. Mulch annually with leaf mould or composted bark.
After flowering, deadhead where practical, to promote vegetative growth rather than seed production. Pruning group 8 – after flowering, lightly trim or prune back shoots that spoil symmetry. Rhododendrons will grow back from old wood, and can be cut back severely for renovation pruning.
Most dwarf alpines are suitable for rockeries, small borders or the foreground of larger borders. They enjoy full sun in cooler conditions, provided the soil remains moist. All require an acid soil; work in plenty of peat and leaf mould. Feed with Miracid from April till August. All are evergreen.
Rhododendrons are not usually prone to insects or diseases. They can develop a condition called chlorosis, which is characterized by yellowing of a leaf between dark green veins. Chlorosis can be caused by malnutrition caused by alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency or magnesium deficiency. A combination of acidification with sulphur and iron supplements such as chelated iron or iron sulphate will usually treat this problem. Chlorosis can also be caused by nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer.
To propagate, surface sow seed in ericaceous compost or fine moss peat, as soon as ripe, in containers in a cold frame. Rhododendrons hybridise freely and may not come true from garden-collected seed. Root semi-ripe cuttings in late summer, layer in autumn or graft in late winter or late summer.
Some species are poisonous to grazing animals. These Rhododendrons have a toxin called grayanotoxin in their pollen and nectar. People have been known to become ill from eating honey made by bees feeding on rhododendron and azalea flowers. Xenophon described the odd behaviour of Greek soldiers after having eaten honey in a village surrounded by rhododendrons. Later, it was recognized that honey resulting from these plants has a slightly hallucinogenic and laxative effect. The suspect rhododendrons are Rhododendron ponticum and Rhododendron luteum (formerly Azalea pontica), both found in northern Asia Minor. Eleven similar cases have been documented in Istanbul, Turkey during the 1980s. Rhododendron is extremely toxic to horses, with some animals dying within a few hours of ingesting the plant, although most horses tend to avoid it if they have access to good forage.
The Glendoick Bird Hybrids
The Bird series of dwarf rhododendrons are being developed at Glendoick Gardens, in Scotland, and are classified as Dwarf Lepidote Hybrids.
The great plant hunters Ludlow and Sherriff returned to Britain in the 1950s. George Sherriff and his wife started a garden only 50km away from Glendoick and they became great friends of the Coxes. On an early visit to their home, Ascreavie, Peter Cox spotted a dwarf yellow-flowered rhododendron species with enormous bowl-shaped flowers for the size of the plant which turned out to be a Ludlow and Sherriff introduction Rhododendron ludlowii.
The Sherriffs allowed Peter to take some pollen home, which he applied to R. chryseum (now R. rupicola var. chryseum.) In due course, the hybrid R. 'Chikor' was selected and named from this cross and which was given an Award of Merit and later a First Class Certificate by the Royal Horticultural Society.
A chikor is a game bird and this started the theme of naming all dwarf lepidote hybrids after birds, another prime interest of Peter's. From then on, several dwarf crosses were made every year with Kenneth Cox starting to make his own crosses in the early 1980s. There are now almost 25 Glendoick birds which are popular with gardeners and rhododendron collectors in many parts of the world.
BRAMBLING 90cm. New Glendoick hybrid with brightest pink flowers in multiple clusters in April. Fine dark foliage.
CHIFF CHAFF 60cm. Masses of creamy yellow flowers in early May. A neat bush with handsome dark foliage. One of the original bird hybrids, raised in the 1960s.
CHIKOR 30cm. Bright yellow flowers in May. The first Glendoick Bird hybrid. Compact twiggy growth. Needs cool roots & good drainage.
CRANE 75cm. Creamy-white flowers in April. Hardy, very free-flowering and easy to please. One of the best white dwarf hybrids.
CURLEW 40cm. Comparatively large, beautiful, open-faced yellow flowers in April-May. Neat spreading habit and good foliage. Expanding buds need frost protection.
EGRET 60cm. Masses of tiny white bells in May. Compact, with shiny, deep green leaves, quite unlike any other hybrid.
EIDER 60cm. Pure white long-lasting flowers in April. Flowers relatively frost resistant. Foliage yellowish-green.
EUAN COX 15cm. Tight glossy foliage and fine yellow flowers on every shoot in late May. The one hybrid made by nursery founder Euan Cox.
GOOSANDER 75cm. Flat-faced yellow flowers with red spots in March-April. New growth reddish-bronze. Not for gardens colder than Glendoick. Semi-deciduous after cold winters.
MERGANSER 45cm. Freely produced yellow bells in May. Very neat habit with dark green foliage.
PINTAIL 60cm. Masses of spectacular brightest pink flowers in multiple trusses in April. A compact plant with good foliage.
PIPIT 20cm. Charming flat-faced pink flowers with darker markings in late May. A natural hybrid from Nepal. Needs extra care.
PTARMIGAN 30cm. The 'Snow Grouse' is covered every year by a carpet of pure white flowers in March-April. Flowers open over a long period during spells of mild weather, so it nearly always puts on a show. Creeping/spreading habit.
QUAIL 30cm. Bright red buds open to deep reddish-pink in April-May. Compact habit. Very free-flowering, the flowers last best in part-day shade. Almost a true red lepidote dwarf.
RAZORBILL 60cm. A remarkable plant with brightest pink long-lasting flowers late April-May, in tight upright trusses. Attractive crinkled leaves on a sturdy plant.
SWIFT 60cm. Fine yellow flowers, strongly spotted red, very freely produced in May. Not for gardens colder than Glendoick. Like ‘Curlew’ but a bit later flowering and more bud hardy.
TINKERBIRD 75cm. Masses of scented cream-white flowers in early May. A real breakthrough: a compact, scented dwarf which grows outdoors at Glendoick. Best in a sheltered site. Surprisingly bud hardy. Also good as a pot plant.
TREE CREEPER 30cm. Pink buds opening to flower pink on outside cream inside, giving an attractive two-toned effect. Compact habit. Very free-flowering. Flowers last best in part day shade.
TURAÇO 75cm+. Masses of pale pink flowers in April-May. A vigorous but tidy dwarf. The best pale pink hybrid of this type.
WAXBILL 75cm. Eye-catching, curious tubular pale pink flowers in April. A vigorous but tidy grower with bronzy new growth. Not for gardens colder than Glendoick.
WHEATEAR 75cm. Distinctive tubular cream flowers, striped pink in April. Vigorous but tidy grower with bronzy new growth. Not for gardens colder than Glendoick.
WIGEON 60cm. Fine slightly glaucous foliage, compact habit and saucer-shaped pink flowers, spotted deeper, in May.
WREN 20cm. Smothers itself with clear yellow flowers in May. Popular with rock garden enthusiasts, and forms a tight mat of attractive, shiny leaves.
Also by Cox:
Teal (3ft) Campanulate flowers in light greenish yellow. May.
Other bird rhododendrons
Arctic Tern - A compact, upright, free-flowering shrub with glossy green leaves and tubular flowers, white tinged green in globular heads. Height 1m. Moist well-drained acid soil in sun. Apr.-May. (Needs full sun to stay compact) Hybridised by Larsen
Blue Tit – Purple flowers, height 2ft, March/April. Hybridised by Waterer.
Yellow Hammer - A slender hybrid with small tubular flowers of clear empire yellow in clusters of two or three. Height 1m. Sunny site in acid soil that doesn't dry out. Mar.-Apr. Hybridised by Waterer.
Humming Bird - (2/3ft) Deep rose-red. April/May.
Phalarope - A small shrub with shiny green leaves and masses of open bells of lilac pink. Height 1m. Moist well-drained acid soil in sun or part shade.
Sanderling Pure white flowers with dark stamens, this is a beautiful early-flowering hybrid (March). Foliage semi-deciduous. Final Height : 3-4.5ft
For more information, visit:
The American Rhododendron Society at http://www.rhododendron.org/index.h
Their listing of cultivars is at http://rhododendron.org/rhododendro
Glendoick Gardens at http://www.glendoick.com
Their page on the dwarf lepidote hybrids is at http://www.glendoick.com/content.php?pa
And here are the images at Photobucket:
Aren't they gorgeous?