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Walk through any mature dry zone forest in Sri Lanka — in Yala, Wilpattu, Bundala, Kumana, or Wasgamuwa — and sooner or later you will find yourself standing beneath a Palu tree (Manilkara hexandra). Known locally as Palu (පළු) and sometimes called Ceylon Ironwood, this is not a tree that announces itself with flamboyant flowers or dramatic silhouettes. It is quieter than that. But once you know what you are looking at, you begin to realise that almost everything in the dry zone forest organises itself around it.
A Tree Older Than Most of What We Know
The Palu is not a newcomer. It is native to the Indian Subcontinent and extends across Indo-China — Bangladesh, India, Sri Lanka, Myanmar, Thailand, Vietnam, and Cambodia — and it has been part of Sri Lanka’s forests since long before human civilisation took root here. In Sanskrit literature, it appears as Kshirini, meaning “the Milk Tree,” a reference to its sticky white latex sap. That name is over 3,000 years old.
In Sri Lanka’s dry zone, the Palu is what ecologists call a dominant canopy species — the most important tree in the tropical semi-deciduous forests of the north, east, and south. A large specimen, with a trunk circumference of two to three metres and a height of 25 to 30 metres, may be anywhere from 300 to 500 years old. Standing beneath one, you are in the presence of a living record that predates the colonial era, the fall of the Kandyan Kingdom, and possibly the construction of some of the ancient tanks that still irrigate the surrounding landscape.
Built Like Iron, For Good Reason
The common name Ceylon Ironwood is not an exaggeration. Palu wood is extraordinarily dense — at its hardest, reaching around 1.08 grams per cubic centimetre, which means a block of it will sink in water. This density makes it naturally resistant to termites and rot, and historically it was one of the most sought-after timbers in the region, used for railway sleepers, bridge construction, and heavy structural work that needed to withstand monsoon conditions year after year.
That same density is part of why old Palu trees survive in the landscape when so much else has been cleared. They are simply very difficult to fell and very slow to decay. The bark is grayish, deeply furrowed, and rough to the touch — practical armour for a tree that has been standing through droughts, fires, and centuries of dry zone weather.
The leaves are worth examining closely. Thick, waxy, and oval with a slightly notched tip, they are designed to retain moisture in conditions where water is precious. In the sustained heat of a dry zone summer, the Palu’s leaves function as efficient water vaults — minimising loss while the tree waits, unhurried and patient, for the rains to return.
When the Iron Tree Softens
For most of the year, the Palu is a tree of quiet presence. But between May and July, something shifts. The tree produces small, golden, oval berries in dense clusters — sweet, scented, and produced in extraordinary abundance. And when that happens, the forest reorganises itself around the fruit.
The most dramatic response comes from the Sri Lankan Sloth Bear. For this animal, the Palu fruiting season is the event of the year. Bears that are otherwise elusive, mostly nocturnal, and highly reluctant to be observed will climb high into the Palu canopy in broad daylight and spend hours — sometimes entire days — feeding from the branches. Their long, curved claws, evolved primarily for tearing open termite mounds, serve them equally well for gripping the rough Palu bark as they haul themselves upward.
The fruits are not just attractive — consumed in large quantities, they can have a mildly intoxicating effect. It is not unusual to find a bear dozing in the upper branches of a Palu, drowsy from a sustained session of gorging, apparently unwilling or unable to descend. May and June are considered the best months to observe sloth bears across Sri Lanka’s national parks, and the Palu is the reason.
Below the bears, the forest floor comes alive. Fruit knocked loose from the canopy feeds spotted deer, wild boar, and gray langurs. Elephants arrive and work the lower branches with their trunks. The Palu, in fruiting season, functions less like a tree and more like a communal dining hall — one that serves every level of the forest simultaneously.
The Architecture of a Home
Old Palu trees develop another quality over time: their centres often become hollow, creating deep internal cavities that run through the trunk. For the dry zone’s cavity-nesting species — hornbills, parakeets, and various owls — these hollows are prime real estate. The rough, deeply furrowed bark also makes the Palu one of the easiest trees in the forest for wildlife to grip and scale, which partly explains why it becomes such a focal point for animal activity regardless of the season.
Naturalists working in the dry zone have long noted that leopards will occasionally use the base of very large, hollow Palu trees as sheltered resting points — though this is field observation rather than formally documented behaviour. Given the tree’s scale and the protection offered by its massive buttressing roots and dense canopy, it is not difficult to understand the appeal.
The Village Pharmacy of the Dry Zone
The Palu’s relationship with people is as old as its relationship with wildlife. The white latex sap has been used in Ayurvedic medicine for centuries as a cooling agent. The bark has traditional applications for stomach complaints and is noted for its astringent properties. The Vedda people — Sri Lanka’s indigenous forest communities — are recorded as having preserved Palu berries in wild honey, creating a concentrated, long-lasting food source that could sustain them through the dry season when other foods were scarce.
The fruit itself is edible and pleasant, with a sweet flavour that has made it a seasonal treat for rural communities living near the dry zone forests for generations.
A Tree Under Threat
For all its resilience, the Palu faces a serious conservation problem. Research conducted across Bundala, Polonnaruwa, Udawalawe, and Yala has found that natural regeneration of the species is severely compromised in many areas. In Bundala National Park in particular, the situation has been described as critical — young Palu seedlings are extraordinarily rare, with studies recording as few as one individual per hectare in some plots. Without young trees establishing themselves, the ageing population of large specimens has no replacement generation.
The causes are complex: poor seed germination conditions, competition from invasive plant species, disease, and the cumulative impact of decades of disturbance. A forest that loses its Palu does not simply lose one species — it loses the structural backbone of an entire ecosystem. The shade, the fruit, the hollows, the seed dispersal networks built around the tree’s seasonal rhythms — all of it unravels.
Reading the Forest Through a Single Tree
Ecologists sometimes describe the Palu as an indicator species — its presence in large numbers signals a forest that is mature, stable, and relatively undisturbed. A forest with old Palu trees is a forest that has had centuries to develop complexity. A forest without them, or with only ageing specimens and no regeneration, is a forest in slow decline.
For the nature enthusiast, this makes every large Palu tree worth pausing beside. You are looking at something that has outlasted kingdoms, survived droughts, fed generations of bears and deer and people, and provided homes to birds that have nested in its hollows for longer than anyone can remember. It is not simply a tree. It is a record of ecological continuity — and one that, in many parts of Sri Lanka, is becoming harder to find.
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