Peltophorum DUBIUM

Peltophorum DUBIUM - Yellow poinciana, Peltophorum dubium, Yellow jacaranda, Yellow flame tree, Rusty caesalpinia, Caesalpinia DUBIA.

Peltophorum is a genus of deciduous or semi-deciduous trees in the legume family (Fabaceae), comprising about a dozen species distributed across tropical and subtropical regions of South America, Africa, and Asia. Species of the genus grow along riverbanks, on the edges of seasonally dry forests, and in savannas.

Members of the genus are trees with delicate, bipinnate foliage and a spreading crown; the bark is smooth and grayish-brown. The fruit is a flat, indehiscent winged pod.

Flowering is profuse - numerous bright yellow flowers are gathered in large paniculate inflorescences at the ends of shoots; during flowering, the tree crown is almost completely hidden beneath the flowers. The bark of many species in the genus is rich in tannins and has long been used to obtain a yellow-brown dye.

Peltophorum dubium is a large semi-deciduous tree 15-25, occasionally up to 30 m (49-82, occasionally up to 98 ft) in height, with a straight trunk and an open crown, growing along riverbanks in seasonally moist forests of South America - in southern Brazil, northeastern Argentina, Paraguay, and Uruguay. Leaves are bipinnate, bright green, giving the crown an airy lacy appearance.

Flowering is profuse and vivid - numerous yellow flowers, gathered in large paniculate inflorescences, completely cover the crown of the tree. The fruit is a flat indehiscent pod with a winged margin that facilitates wind dispersal.

Seeds of Peltophorum dubium are flat, oval, dark brown, about 1 cm (0.4 in) long, enclosed in a dense indehiscent winged pod. The coat is hard and poorly permeable to water, which substantially delays germination without pretreatment.

Before sowing, seeds are poured over with hot, nearly boiling water (90-95 °C (194-203 °F)) and left to cool in the same water for 24 hours - such treatment effectively breaks down the hard seed coat. After this, seeds are soaked in a 1% potassium permanganate solution for 1-2 hours, and then for 12-24 hours in warm water with the addition of a growth stimulant: SUPERthrive, HB-101, Aminozol, Epin, or Zircon. They are then sown in a light breathable substrate, moistened with a spray bottle, placed in a propagator or covered with plastic wrap, and germinated in the light, but not in direct sun, at a temperature of 23-25 °C (73-77 °F) and above.

Germination under favorable conditions begins in as little as 1-2 weeks; main germination is usually completed within 3-4 weeks, while individual seeds, especially those insufficiently treated, may delay longer. Sprouts require ventilation; it is important to avoid overwatering and desiccation of the sowing. After the appearance of several true leaves, seedlings are pricked out into individual pots.

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Peltophorum is light-loving and tolerates direct sun well, especially during morning hours - for a mature plant, the brightest window is chosen, preferably south-facing.

In summer, a temperature around 20-22 °C (68-72 °F) suits the plant; in winter, cool conditions are required - around 10-12 °C (50-54 °F), with a short-term drop to 5 °C (41 °F) being permissible. Such a cool winter period promotes flowering the following year.

Watering is moderate, 2-3 times a week in summer as the top layer of the substrate dries out; in winter it is reduced, but the substrate is not dried out completely. The plant is not demanding regarding air humidity, but the crown can be periodically wiped down or misted.

A nutrient-rich loose substrate is suitable, such as prepared potting soil for pelargoniums with added sand. Repotting of young plants is carried out annually in spring into a deep container; older plants are repotted less frequently, as needed, or one may simply replace the top layer of substrate.

Feeding required is moderate - usually slow-release fertilizer at planting is sufficient; if necessary during active growth, one can feed with a fertilizer for flowering plants.

The size and shape of the crown are set by annual pruning in early spring, before active growth begins.