Notes
for bonsai cultivation
Zelkova
parvifolia/Japanese Elms are often sold as indoor bonsai and as
such are acclimatised to indoor growing conditions, Japanese Elms
sold as outdoor bonsai and all other species of Zelkova should
be cultivated outdoors. Japanese Elms grown indoors (or in climates
with very mild winters) will remain evergreen where as outdoor
cultivation results in a deciduous tree. Ensure indoor trees do
not become too cold in their first winter outside. Zelkovas should
be able to cope with the adverse growing conditions indoors though
they are never as vigorous as their outdoor counterparts.
Position
(Indoors)
Well lit, cool position on a sunny windowsill during the winter.
Keep up humidity levels. Place outside from May onwards after
last frosts have finished. Try to keep outside until Autumn when
the leaves can be allowed to fall naturally before bringing indoors.
(outdoors)
Outdoor Zelkovas/acclimatised Zelkovas are hardy to frost though
temperatures below -5°C can result in fine branches dying back
and root damage so should be afforded some protection. Frost protection
can include placement in darkened outhouses and garages as when
out of leaf Zelkovas do not require light.
Watering
(indoors)
Never allow compost to dry out, keep the compost evenly moist.
Check the compost daily but only water when necessary. Watering
daily as a routine results in sodden compost, leading to lack
of vigour, rootrot
and eventually death.
(outdoors)
As with indoor watering though during periods of strong sun, high
temperatures or strong growth in the Spring, trees can need far
more frequent watering.
Feeding
(indoors)
Balanced feed weekly through Spring and Summer. Monthly through
the winter. Do not feed when out of leaf.
(outdoors)
Once buds open in Spring, feed weekly with high nitrogen for first
month then every two weeks until late summer with balanced feed.
Repotting In Spring as buds extend annually until around
10years old or more and then repot as required. Trees overwintered
indoors can be repotted in Autumn when brought indoors after leafdrop.
Repot in basic soil mix.
Pruning Allow shoots to extend 3 or 4 nodes then prune
back to 1 or 2 leaves as required Larger-leaved Zelkovas respond
well to leaf cutting in Summer
Wiring In mid-summer though indoor trees can be wired mid-winter
particularly if out of leaf. Care should be taken as bark marks
easily.
Propagation Sow seed outdoors in Autumn or Spring. Greenwood
cuttings in Summer. Hardwood cuttings in Winter. Air-layering
after spring growth has hardened.
Pests and diseases Zelkova bonsai as with all Elm bonsai
are not affected by Dutch Elm Disease as the beetle requires the
volume of wood only available to it in fully grown mature trees.
An attack (if it were to happen) would easily be dealt with by
systemic insecticides and fungicides on a potted tree in comparison
to the problems associated with eradicating Dutch Elm Disease
on a fully-grown tree in the ground.
Watch
for aphids, leafhoppers, leafspot and gall mites.
Styling Suitable for all forms and sizes- especially good
for the broom form which replicates the natural shape of field-growing
Zelkova.
