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Useful Temperate Plants

Rhododendron yedoense

Maxim.

Ericaceae


Rhododendron yedoense is the name given by Maximowicz in 1886 to a double-flowered garden form of an azalea that grows wild in Korea. Unfortunately this azalea was not described as a species until many years later and must therefore be treated as a variety of its own cultivated offspring. The name of the wild form is therefore Rhododendron yedoense var. poukhanense (H.Lév.) Nakai[
11
Title
Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement.
Publication
 
Author
Bean. W.
Publisher
Murray
Year
1981
ISBN
-
Description
A classic with a wealth of information on the plants, but poor on pictures.
].

+ Synonyms

Azalea poukhanensi hort.

Rhododendron poukhanense H.Lév.

Rhododendron hallaisanense H.Lév.

Common Name:

No Image.

General Information

Rhododendron yedoense is a compact, densely-branched deciduous shrub growing 100 - 200cm tall and more wide[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
,
275
Title
Flora of Japan
Publication
 
Author
 
Website
http://www.foj.info
Publisher
 
Year
0
ISBN
 
Description
An on-line version of the flora - an excellent resource.
]. The plant can be evergreen in areas with mild winters[
352
Title
KemperCentreForHomeGardeningPlantFinder
Publication
 
Author
 
Website
http://www.mobot.org/gardeninghelp/plantfinder/
Publisher
Missouri Botanical Garden
Year
0
ISBN
 
Description
Basic cultivation details, plant uses, habitat etc for several thousand species of plants, mainly from the temperate zone.
].
The plant is harvested from the wild and also cultivated for medicinal use. It is an ingredient of commercial cosmetic preparations and is also grown as an ornamental in gardens[
317
Title
Mansfeld's Database of Agricultural and Horticultural Plants
Publication
 
Author
 
Website
http://mansfeld.ipk-gatersleben.de/pls/htmldb_pgrc/f?p=185:3:4292127278597336
Publisher
 
Year
0
ISBN
 
Description
Terse details of a huge range of useful plants.
].

Known Hazards

Although no specific mention of toxicity has been seen for this species, all parts of Rhododendron species (including the leaves, flowers and pollen) contain greater or lesser amounts of the toxic compound andromedotoxin (also known as grayanotoxin). Rarely lethal to humans (and used medicinally in some herbal disciplines), this compound causes dose-dependant overstimulation of the central nervous system with symptoms including various cardiovascular effects (mainly low blood pressure and cardiac rhythm disorders); nausea and vomiting; and a change in consciousness. The effects commence shortly after ingestion and last around two days. These effects are also transferred to honey made from the nectar of the flowers. In some parts of the world bees are used to deliberately produce a honey rich in andromedotoxin which is then eaten for its supposed medicinal, hallucinogenic and aphrodisiac effects.
In contrast to humans, many other creatures are more susceptible to the toxin and it has sometimes proved lethal to grazing animals and household pets. Some forms of honeybees are also killed by the toxin (resistant forms of the bee are used for honey production). Bumblebees are not affected, however, and are also more efficient in pollinating rhododendron flowers, so one theory is that the toxin is produced by the plant in order to favour the bumblebee and improve fertilization rates[
1668
Title
Grayanotoxin Poisoning: ‘Mad Honey Disease’ and Beyond
Publication
Cardiovasc Toxicol (2012) 12:208-215
Author
Jansen S.A. et al
Website
https://doi.org/10.1007/s12012-012-9162-2
Publisher
 
Year
2012
ISBN
 
Description
An in-depth review of the literature on the toxic effects of a toxin widely found in the family Ericaceae
].

Botanical References

11
Title
Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement.
Publication
 
Author
Bean. W.
Publisher
Murray
Year
1981
ISBN
-
Description
A classic with a wealth of information on the plants, but poor on pictures.
,
275
Title
Flora of Japan
Publication
 
Author
 
Website
http://www.foj.info
Publisher
 
Year
0
ISBN
 
Description
An on-line version of the flora - an excellent resource.

Range

E. Asia - southern Japan (Kyushu), Korea

Habitat

Stony mountain slopes, on rocks along streams; at elevations up to 1,800 metres[
275
Title
Flora of Japan
Publication
 
Author
 
Website
http://www.foj.info
Publisher
 
Year
0
ISBN
 
Description
An on-line version of the flora - an excellent resource.
].

Properties

Medicinal Rating *  *
Other Uses Rating *  *
HabitDeciduous Shrub
Height1.50 m
PollinatorsBees, Insects
Cultivation StatusCultivated, Ornamental, Wild

Cultivation Details

Rhododendron yedoense is native to the temperate zone of Korea, where it can be found at elevations up to1,800 metres. A very cold-tolerant plant, when fully dormant it can withstand temperatures down to about -30°c Although cold-tolerant when dormant, the flowers and young growth of Rhododendrons are very susceptible to damage by late frosts in regions where these are likely to occur after new growth has commenced in the spring[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
].
Rhododendron species generally succeed when grown in a non-compacted, humus rich lime free soil and a position with some shade, preferably light woodland shade. They strongly dislike soils of a dry arid nature, heavy soils or clays[
1
Title
RHS Dictionary of Plants plus Supplement. 1956
Publication
 
Author
F. Chittendon.
Publisher
Oxford University Press
Year
1951
ISBN
-
Description
Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [200]).
]. Prefers a peaty or well-drained sandy loam[
1
Title
RHS Dictionary of Plants plus Supplement. 1956
Publication
 
Author
F. Chittendon.
Publisher
Oxford University Press
Year
1951
ISBN
-
Description
Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [200]).
]. Succeeds in sun or shade, the warmer the climate the more shade a plant requires[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
]. Requires a pH between 4.5 and 5.5[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
].
Rhododendron species are mainly woodland species that grow well in the dappled shade and shelter given by the other woodland plants. They are surface-rooting species with a fibrous root system, however, and do not grow well close to trees that are also surface-rooting, nor do they do well with ground cover or other small plants growing over or into their roots[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
,
352
Title
KemperCentreForHomeGardeningPlantFinder
Publication
 
Author
 
Website
http://www.mobot.org/gardeninghelp/plantfinder/
Publisher
Missouri Botanical Garden
Year
0
ISBN
 
Description
Basic cultivation details, plant uses, habitat etc for several thousand species of plants, mainly from the temperate zone.
].
Plants form a root ball and are very tolerant of being transplanted, even when quite large, so long as the root ball is kept intact[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
].
This species is often used in breeding programmes to develop ornamental garden forms[
352
Title
KemperCentreForHomeGardeningPlantFinder
Publication
 
Author
 
Website
http://www.mobot.org/gardeninghelp/plantfinder/
Publisher
Missouri Botanical Garden
Year
0
ISBN
 
Description
Basic cultivation details, plant uses, habitat etc for several thousand species of plants, mainly from the temperate zone.
].

Edible Uses

None known

Medicinal

Some caution is advised in the medicinal usage of this plant - see the notes above on toxicity.

The plant is used medicinally[
317
Title
Mansfeld's Database of Agricultural and Horticultural Plants
Publication
 
Author
 
Website
http://mansfeld.ipk-gatersleben.de/pls/htmldb_pgrc/f?p=185:3:4292127278597336
Publisher
 
Year
0
ISBN
 
Description
Terse details of a huge range of useful plants.
]. No more information is given.

Other Uses

An extract of the flowers is used as an ingredient in commercial cosmetic preparations as a skin conditioner[
1243
Title
CosIng
Publication
 
Author
 
Website
http://ec.europa.eu/growth/tools-databases/cosing/
Publisher
 
Year
0
ISBN
 
Description
CosIng is the European Commission database for information on cosmetic substances and ingredients.
].
An extract of the branches and leaves is used as an ingredient in commercial cosmetic preparations as a skin conditioner[
1243
Title
CosIng
Publication
 
Author
 
Website
http://ec.europa.eu/growth/tools-databases/cosing/
Publisher
 
Year
0
ISBN
 
Description
CosIng is the European Commission database for information on cosmetic substances and ingredients.
].

Propagation

Seed - surface sow in a shady part of the greenhouse in late winter or early spring[
78
Title
Propagation of Trees, Shrubs and Conifers.
Publication
 
Author
Sheat. W. G.
Publisher
MacMillan and Co
Year
1948
ISBN
-
Description
A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
,
113
Title
The Reference Manual of Woody Plant Propagation.
Publication
 
Author
Dirr. M. A. and Heuser. M. W.
Publisher
Athens Ga. Varsity Press
Year
1987
ISBN
0942375009
Description
A very detailed book on propagating trees. Not for the casual reader.
]. Another report says that the seed is best sown in the autumn as soon as it is ripe[
188
Title
The RHS Gardener's Encyclopedia of Plants and Flowers
Publication
 
Author
Brickell. C.
Publisher
Dorling Kindersley Publishers Ltd.
Year
1990
ISBN
0-86318-386-7
Description
Excellent range of photographs, some cultivation details but very little information on plant uses.
]. Germination is variable and can be quite slow. Prick out the seedlings into individual pots as soon as they are large enough to handle and grow the pots on in a shady frame for 18 months before planting them out into their permanent positions[
78
Title
Propagation of Trees, Shrubs and Conifers.
Publication
 
Author
Sheat. W. G.
Publisher
MacMillan and Co
Year
1948
ISBN
-
Description
A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
].
Cuttings of half-ripe wood, 5 - 8cm with a heel, mid summer in a frame. Plant out in spring. Fair percentage[
78
Title
Propagation of Trees, Shrubs and Conifers.
Publication
 
Author
Sheat. W. G.
Publisher
MacMillan and Co
Year
1948
ISBN
-
Description
A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
].
Cuttings of mature wood, late autumn in a frame[
113
Title
The Reference Manual of Woody Plant Propagation.
Publication
 
Author
Dirr. M. A. and Heuser. M. W.
Publisher
Athens Ga. Varsity Press
Year
1987
ISBN
0942375009
Description
A very detailed book on propagating trees. Not for the casual reader.
].
Layering in the autumn. Takes 12 months[
78
Title
Propagation of Trees, Shrubs and Conifers.
Publication
 
Author
Sheat. W. G.
Publisher
MacMillan and Co
Year
1948
ISBN
-
Description
A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
].
Division.
Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2021-03-08. <temperate.theferns.info/plant/Rhododendron+yedoense>

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