Indian oak
Barringtonia acutangula
A medium tree whose long red flower clusters hang like curtains in the rainy season and carpet the ground as they fall.
Care and placement
Likes full sun or light shade and fertile, moist but draining soil, with fairly good drought and wet-foot tolerance; frost-sensitive; avoid heavy pruning and too much nitrogen if you want flowers; propagated by seed or air layering.
Draft mature dimensions
Maximum height (cm): 1000 cm · Maximum spread (cm): 600 cm
Things to consider
The sources disagree on toxicity: Wikipedia says young leaves are eaten in Vietnam, while Top Tropicals lists the plant among those with toxic parts, so it is not claimed safe. Do not eat it or use it as medicine; wear gloves when pruning and keep children and pets from chewing it. In a city, plan for flowers and fruit falling under the crown.
How to grow and care for it
Planting and pot
The tree grows about 8–15 m tall (growers often see 4–10 m) with a dense, fairly wide crown, so it needs open, fertile ground in full light. The sources give no safe distance from buildings, pipes, pavements or overhead lines and say nothing on root behaviour, so a site survey is needed before planting. Young trees need a stake and a guard so wind does not rock the base. Planting on a pavement or public land needs permission from the landowner or the tree authority.
Light
A sun lover that flowers best in plenty of light, though it tolerates light shade. It is frost-sensitive: Top Tropicals places it in warm USDA zones 9–10 and advises protection from freezing, so it does not suit high mountain areas with frost.
Watering
It grows wild along freshwater rivers, so keep the soil moist while young; once established it is fairly tolerant of both drought and wet feet. In the rainy season, drain off excess water if the soil stays soaked for long.
Feeding
Spread well-rotted manure around the base and water it in; Vietnamese growers apply NPK about every 3–4 months and do not overfeed. A tree that is over-fed may put out leaves and few flowers.
Pruning
Prune lightly to keep the crown tidy; a Vietnamese source warns that too much pruning makes the tree reluctant to flower. Remove dead, broken and crowded branches, and leave high crown work to a trained arborist.
Propagation
Usually propagated from seed; in Vietnam, air layering from the parent tree in the warm, wet season or cuttings are also used. Layered plants keep the parent's traits, such as flower colour.
Pests and common problems
In the city: flowers hang in long clusters up to about 40–50 cm, the spent ones drop under the crown and the small fruit falls too, so clearing is needed; the sources say nothing on pollen allergy. Stem borers can make leaves wilt and branches die back, so look for bore holes on the trunk; leaf caterpillars also occur. Frost harms it. Young trees rock easily in strong wind without a stake.
For more flowers
For plenty of flowers: give enough sun, feed moderately so the tree does not just grow leaf, and avoid over-pruning. The long red flower clusters hang down, open at night and peak in the rainy season, around July–August according to one Vietnamese source.