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Aralia - Aralia, Dizygotheca
or Polyscias
General Information: Aralia are ornamental shrubs, although the hardy
varieties have compound leaves up to three feet in length, making
them unsuitable for bonsai. All can be successfully grown as
indoor bonsai.
Lighting:
Prefers a bright location with indirect sun. Can do well with
relatively low light levels.
Temperature:
Never below 60F for the Aralia species listed. 50F is the minimum
for Polyscias, although it prefers a winter temperature of between
59-80F. One of the few plants that actually grows better indoors
as it does not appreciate direct sun and is very intolerant of
wind.
Watering:
Needs a lot of water, and constantly moist soil, but can develop
root rot if water is allowed to stagnate around the roots. Misting
is essential.
Feeding:
Every two weeks during growth, every six weeks in winter. Success
using Osmocote has also been reported.
Pruning and wiring:
Usually shaped by pruning rather than wiring. Cut shoots back
to one or two leaves when they have reached four or five. Removing
inner branches results in a more tree-like appearance. Partial
defoliation can be used effectively for leaf reduction.A slow
grower, but will form more buds in very humid conditions such
as a greenhouse or plastic bag. Remove suckers from single-trunk
specimens to encourage fuller trunk growth.
Propagation:
The best method is to use root cuttings or air-layering. The
plant suckers profusely, so division is another option. Softwood
cuttings can be taken in spring, but require bottom heat of 75F,
use of rooting hormone, and a high humidity to root. Seeds may
be planted in autumn, but germination is uncertain.
Repotting:
Every 2-3 years in spring. Use a compact soil mix. but insure
good drainage. Roots tend to be fragile and few, so caution in
repotting is necessary. A deep pot is generally safer than a
shallow bonsai pot. When Polyscias are to be root pruned, it
helps to induce a short dormancy by keeping them at a temperature
of 50F for about three weeks prior to repotting, then returning
them to a temperature of at least 59F immediately afterwards
to stimulate root growth.
Pests and diseases:
Eelworms, mites, scale, verticillium wilt, root rot, alternariose,
bacterial canker.
Some species suitable for bonsai:
- Aralia blacky - Desirable for bonsai because
it forms a large trunk, this Aralia has smooth edged, scroll-shaped
leaves.
- Aralia castor (also called Dizygotheca
castor) -dark green leaves marbled with white.
- Aralia elegantissima (also called Dizygotheca
elegantissima) similar to A. castor, but larger.
- Polyscias fruticosa (also called Aralia
ming) -white bark.
Bibliography:
Ainsworth's "The Art of Indoor Bonsai"
Samson's "Creative Art of Bonsai"
Species information from Thomas (ed.) "The Hearst Garden
Guide to Trees and Shrubs."
- Compiled by Sabrina Caine
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Name or Index by Common Name
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