Wisteria - Wisteria sp.
General information: The wisteria is a
vigorous low-growing vine, a legume, that is very
popular as an ornamental. The wisteria is known for the
beauty of its flowers, which appear in long, cascading
racemes and are usually blue, purplish-blue, pink, or
white. The flowers typically bloom April-June. There are
a number of species which are suitable for bonsai, all
of them being quite similar and varying mainly in the
size and color of their flower racemes and number of
leaflets in their compound leaves. Japanese and Chinese
wisteria are the traditional bonsai subjects, but those
in the southeastern United States where American and
Kentucky wisteria are to be found should have good luck
with them. The racemes and compound leaves of Japanese
wisteria are the longest, with racemes from 8-20 inches
and leaflets numbering 13-19. Chinese wisteria blooms
are 6-8 inches long and the leaflets number 9-13.
American wisteria blooms are the shortest at less than
4.5 inches, and leaflets number 9-15. The flowers of
American wisteria are purplish or white and the seed
pods are hairless. With such small blooms, American
wisteria should be the most suitable for smaller sized
bonsai. The Kentucky wisteria has blooms 6-12 inches
long and leaflets numbering 9-15, and also has hairless
seed pods.
Lighting: Full sun to partial shade.
Temperature: No information is available.
Watering: The wisteria needs lots of water
during the growing season. In summer, after flowering,
place the pot in a tray of water so that the plant can
soak up as much water as it needs. Do not allow the
water to stagnate. Water heavily before and during
flowering.
Feeding: In general, wisteria need more
fertilizer than most bonsai. However, in order to ensure
good flowering, feeding should be minimized during and
immediately following flowering. Fertilize heavily in
spring before flowering and in late summer and autumn,
until the leaves drop. For organic and slow-acting
fertilizers, feed double the usual strength for bonsai,
applying fertilizer at the recommended intervals. For
chemical fertilizer, you can either use it full strength
every other week or you can use it at half strength
every week.
Pruning and wiring: There seem to be as many
differing opinions on training of wisteria as there are
authors on the subject. The training instructions here
are an outline of the recommendations detailed by
Chiharu Imai in Bonsai Today #38. The wisteria is
generally styled to look its best when it is in bloom,
which usually means that the branches are shaped to
support a weeping appearance when the cascading blooms
are present. Wisteria can also be quite pleasing when in
full leaf. In winter, when the branches are
bare, they are not very attractive. Structural pruning
and wiring are done after the blooms have gone by. The
dry racemes should be cut off, leaving 2-3 shoots at the
base of the raceme. At the same time, pinch back the
tender tips of these
shoots. After this pruning, many tendrils will emerge.
These tendrils grow rapidly, as much as an inch each
day. The tender tips of these shoots should be pinched
back as soon as they have 4-5 sets of leaves. Do not
remove the new shoots until the end of August, otherwise
the plant may set new flower buds and bloom again that
summer, which will weaken the blooms the following
spring. After August, completely
remove any shoots that are not going to be used as
branches. The wisteria sets blooms on the short lateral
shoots rather than on the tips of the growing shoots, so
removing the tips will not endanger the following
spring's bloom. If you want a good bloom in the spring,
remove any seed pods as soon as they appear so that the
plant does not expend strength developing seeds.
Propagation: Cuttings, layering
Repotting: The roots of wisteria are
extremely strong and vigorous. Young specimens should be
repotted every year, and the roots must be combed out
and reduced aggressively. Older trees should be repotted
every 1-2 years. Wisteria should be repotted in early
spring or in autumn. Pot in a fairly deep container to
accommodate the vigorous roots. Rémy Samson recommends a
mix of 1 part loam and 1 part leaf mould. Simon and
Schuster's recommends 50% soil, 30% peat, and 20% coarse
sand. In Bonsai Today #38, Chiharu Imai says that in
Japan the usual mix is 7 parts akadama (a material
similar to Turface), 2 parts sand, and 1 part peat moss.
He also says that normal bonsai mix or even a sandy loam
can be used. The roots of wisteria often display small
black nodules, which are nitrogen-fixing nodules.
Wisteria can be attacked by nematodes, which manifest as
larger, wart-like swellings in the roots.
Pests and diseases: The seeds and seed pods
of wisteria are poisonous. Do not allow children or
animals to ingest them.
Wisteria species include:
- Japanese Wisteria - Wisteria floribunda
- Chinese Wisteria - Wisteria sinenis
- American Wisteria - Wisteria frutescans
- Kentucky Wisteria - Wisteria macrostachya
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