WISTERIA BONSAI

The Wisteria Bonsai: A Cascade of Lilac Flowers

The Wisteria(Wisteria floribunda or sinensis) is the quintessential spring bonsai tree. When it blooms, its colorful clusters (lilac, white or pink) descending from bare branches are a breathtaking sight. It is a very vigorous climbing plant, almost weedy in the wild, which makes it easy to grow but challenging to keep "at bay" as a bonsai. It is not grown for its fine branching (which is coarse), but for the elegance of its flowers and the charm of its twisted trunk.

Origin & species

Native to China and Japan ( W. Sinensis and W. Floribunda, respectively), it belongs to the Fabaceae (Leguminosae) family. The Japanese variety has longer and more elegant clusters, often used for medium/large bonsai trees. The trunk ages beautifully, becoming fluted and muscular.

Exposure and Microclimate

The Wisteria is a sun worshipper.
Full sun all the time. Sun is the fuel needed to differentiate flower buds for the following year. If you keep it in the shade, you will have lots of green leaves and zero flowers.
It is not afraid of heat, but in summer it drinks like a sponge.

Watering (The saucer trick)

In summer, Wisteria is one of the very few exceptions to the "no watering" rule.
During flowering and in the hot months (June-August), it drinks so much that it is almost impossible to keep up with just the watering can.
Tip: Keep the pot submerged in a saucer with 2-3 cm of water during scorching summer days. The roots will drink it all up in the day. Remove the saucer as soon as temperatures drop or in winter.

Water quality

It is undemanding, but appreciates abundant water. Lime water is not the best in the long run, but it tolerates it better than a maple.

Substrate

Standard soil, but one that retains water.

  • Recommended mix: 60% Akadama (or fine expanded clay) and 40% Universal Potting Soil.
  • Do not use only pumice or pure akadama if you cannot water three times a day in summer.

Repotting

Repot often (every 1-2 years young ones, 2-3 old ones) because the roots fill the pot in no time.
When: In fall (after leaf fall) or very early spring.
Be drastic with large roots; the Wisteria will throw it all back up.

Fertilization

Strategy is key for flowers.
Spring (post-flowering): Balanced fertilizer to restore energy.
Summer/Fall: Fertilizer rich in Phosphorus (P) and Potassium (K) and low in Nitrogen. Excess Nitrogen favors leaves at the expense of flowers.

Flowering and fruiting

It blooms in April-May. The flowers appear before the leaves.
After flowering, long, velvety pods form: remove them immediately! Producing seeds costs the tree a lot of energy and could jeopardize flowering the following year.

Pruning

Wisteria throws meter-long shoots in a few weeks.
Summer pruning: Continuously shorten long shoots, leaving 2-3 buds, to maintain shape.
Winter pruning (essential): In January-February, shorten the year's branches leaving only 2-3 buds. Flower buds are the large, round ones at the base of the branches; pointed ones are leaf buds. Do not cut off the round ones!

Tying & bending

Little use is made of wire because the branches swell quickly and the wire soon becomes incarnate. Better to form by pruning ("clip and grow"). If you do use wire, do it on young shoots in summer and check it weekly.

Diseases and pests

Very hardy, but attracts:

  • Aphids: On buds and tender shoots.
  • Rust or Powdery mildew: On leaves late in the season.

Winter & protection

Withstands cold well (down to -10°C in the ground), but in pots best to protect roots from heavy frosts that could damage future flowers already formed.

Annual calendar

  • January-February: Flower bud selection pruning.
  • March-April: Flowering (water a lot!).
  • May: Removing wilted flowers and pods, beginning fertilization.
  • June-August: Water saucer, continuous topping of long shoots.
  • September: Remove saucer, PK fertilization.
  • November-December: Rest.

Useful products for this bonsai

Wisteria Frequently Asked Questions

Why doesn't my wisteria ever bloom?
Common causes: plant too young (from seed it takes 10-15 years, from cuttings/grafts it's quick), too much nitrogen in fertilizer, or incorrect winter pruning that eliminated flowering buds.

Can I keep it indoors?
No, Wisteria is an outdoor plant. In the house it would die from lack of light and winter rest.

Should I repot every year?
Yes, if it is young. The roots are so powerful that they often split the pot if they don't have room. Check in spring if the root ball is too compact.