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Kurume Azalea - Rhododendron
obtusum amoenum
General Information:
The azalea is a member of the genus Rhododendron.
It is an evergreen which in the wild grows as a small shrub (up
to six feet). There are hundreds of azalea varieties. The azalea
used to be considered a separate genus from the rhododendron,
but has recently been reclassified. The Kurume azalea is a hybrid
of R. obtusum and R. kiusianum, both native to
the island of Kyushu, the southernmost island of Japan. They
are often referred to as dwarf, although they may reach 4 to
6 feet in height and spread. Kurume Hybrids are hardier than
the Southern Indian Hybrids.
Lighting: Filtered,
partial sun. Avoid prolonged direct exposure to spring and summer
sun.
Temperature:
Protect the tree (preferably under glass) in the winter, but
do not bring indoors.
Watering: Keep the soil damp, as the roots can dry out easily
and this is fatal to the tree. Water with rain water if possible.
If using tap water that is high in lime, repot the tree every
year to keep the soil acidity high.
Feeding
Feed every 20-30 days with a slow-acting organic fertilizer,
from early spring to late autumn, and apply chelated iron a couple
times a year. Micro nutrients should be applied routinely.
If you prefer to use chemical fertilizers,
feed every two weeks using a half-strength solution of a fertilizer
for acid-loving plants, such as Miracid.
If the tree is repotted in spring, do not
feed until autumn. Do not feed during the hottest month of the
summer.
Pruning and wiring: Prune branches and new shoots in late summer,
using a sealing compound to seal wounds. Azalea can and will
grow shoots from old wood. New shoots at the ends of branches
grow in groups of five. These shoots should be reduced to two
and the remaining shoots shortened to two sets of leaves. Wiring
may be done from spring through summer. Use care when bending
branches, as older branches are brittle. Skipping watering the
day before wiring will make the branches more flexible. You may
need to protect the bark by wrapping the wire with raffia.
Propagation:
usually by cuttings to maintain hybrid characteristics. Take
3 to 4 inch cuttings after spring growth has hardened.
Repotting Repot in the spring after the flowers have gone
by, every year for young trees, every 2-3 years for older trees.
Azaleas like well drained, organic soils with a pH of 4.5 to
5.5. Some growers use pure peat moss, though this is probably
too extreme. Using a soil mixture specifically intended for azaleas
is advisable. Azaleas grow extremely dense, hairy root masses.
Experienced growers of azalea bonsai recommend using a soil mix
that contains no small particles at all, because of the dense
growth of azalea roots. If soil with fine particles is used,
the roots can form mats that shed water, making successful feeding
and watering difficult. When repotting, trim the root ball and
cut out pie-shaped wedges around the outside of the root ball
so that the roots can grow into the gaps.
Pests and diseases:
Aphids, lacebugs, white fly, leafminers, spider mites, scale,
stem boreres. Diseases include petal blight, leaf gall, mushroom
root rot.
Compiled by Sabrina Caine and Thomas L.
Zane
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