The Sesbania Bonsai: The Hummingbird Tree

The Sesbania Punicea, known poetically as the Hummingbird Tree (or "Red Wisteria"), is a bonsai tree that carries with it the allure of South America. Its nickname is no accident: its clusters of deep orange-red flowers are so rich in nectar that they attract these birds to their native areas. It belongs to the Fabaceae family and is loved for its spectacular flowering and pods that, as they dry, tinkle in the wind like maracas (hence the other name "Rattle Tree"). It is an exotic plant, fast growing and visually striking.

Origin & species

Native to Argentina, Brazil and Uruguay, it is a deciduous shrub or small tree (it loses its leaves in winter). It has elegant compound leaves that partially close at night (nictinastia). It is a pioneer plant that loves water and sun.

Exposure and Microclimate

Sesbania loves full sun.
The more sun it gets, the more flowers it will produce. It is not afraid of scorching summer heat. In contrast, shade inhibits flowering and weakens vegetation. In windy areas, the flexible branches will dance smoothly, but watch out for pots small ones that might topple over.

Watering

In the wild, it often grows near waterways. In pots, therefore, it drinks a lot.
In summer, never let the potting soil dry out completely for too long: water generously and frequently. If it suffers from thirst, the leaves will yellow and fall off quickly. In winter, when the plant is bare, reduce watering by keeping the soil barely moist.

Water quality

It is a hardy and tolerant plant. It accepts tap water without any particular problems, although water that is not too limey is always preferable to avoid salt buildup over time.

Substrate

Requires a soil that retains moisture but drains to avoid rot.

• Recommended mix: 40 percent Akadama, 30 percent Pumice and 30 percent Universal Potting Soil or Humus.
• The organic component is higher than in other bonsai trees precisely to meet its high water demand.

Repotting

This is done in spring (April), when temperatures rise.
Sesbania has explosive root growth. Young specimens should be repotted every year or two. It tolerates root pruning well, but always try to balance the foliage (if you cut a lot of roots, shorten the branches as well).

Fertilization

It is a voracious plant. Fertilize regularly from spring through summer.
To support flowering and vigorous growth, use a quality solid organic fertilizer. Suspend fertilization only during full flowering.

Flowering and fruiting

It blooms in late spring/summer. The red clusters are the highlight.
They are followed by pods (legumes) with 4 characteristic wings that contain the seeds.
Caution: If the bonsai is young, remove the pods as soon as they bloom so as not to tire the plant. If you want to hear the "sound of rattles," leave only a couple.

Structure pruning

This is done in late winter by shortening long branches from the previous year.
Sesbania tends to grow haphazardly and quickly: you must be firm with the scissors to maintain a compact shape and an interesting trunk.

Maintenance pruning

During the growing season, prune back any branches that get too long.
Remember that flowers are born on the new shoots: if you continually prune until July, you will cut off future flowers. Let branches grow freely in late spring if you want flowering.

Pruning

This can be done on vigorous shoots in spring to thicken the foliage, but should be discontinued early if the goal is to see red flower color.

Tying & folding

Young branches are green and flexible, easy to bind.
However, they quickly lignify, becoming stiff. Apply wire in spring and check it often because the bark is tender and fast growth leads to rapid rooting.

Diseases and pests

• Aphids: They love buds and tender shoots.
• Whitefly: Sometimes present under leaves in summer if there is little ventilation.

Winter & protections

Not an alpine plant.
In the South, it lives outside. In the North, it withstands brief light frosts (-2°/-4°C), but if the cold is severe it should be sheltered in a cold greenhouse or a protected place (such as an unheated veranda). It fears prolonged frost on its roots.

Annual calendar

• January-February: Rest, dry pruning.
• March-April: Repotting, reviving.
• May-June: Fertilizing, abundant water.
• July-August: Flowering, full sun, plenty of water.
• September-October: Pods ripening, fall fertilizer.
• November-December: Leaf fall, protection.

Useful products for this bonsai

• Quality Universal Potting Soil (To retain water)
• Biogold fertilizer (Complete and balanced nutrition)
• Plastic saucer (Useful for water reserve)
• Coppered aluminum wire (For shaping branches)
• Oblique clippers (For clean cuts)
• Multi-purpose insecticide (Bud protection)

Frequently Asked Questions about Sesbania

Are the seeds poisonous?
Yes, very toxic if ingested. All parts of the plant contain saponins, but the seeds in the pods are very rich in them. Keep the plant away from small children and pets who might chew them.

Why do the leaves close in the evening?
It is a natural phenomenon called "nocturnal nictinasty" (nocturnal movement), typical of many leguminous plants such as Albizia and Tamarind. The plant "sleeps" to conserve heat and moisture.

Can I keep it indoors all the time?
No. It needs direct sun to bloom and to feel the change of seasons (and winter coolness) to go dormant. In the house it would live poorly, spinning and never flowering.