Forest Plants of Kalimantan: Timber, Latex, Rattan and Medicinal Species

Forest plants of Kalimantan supply far more than most visitors expect. The island’s lowland and heath forests have long yielded hard timber, latex, seed fat, climbing canes, traditional medicinal roots and camphor, and the same forests hold carnivorous pitcher plants and a large orchid flora. The main species are sorted by what they give and by the kind of forest they grow in, and the limits that now apply to harvesting and trade follow them. For the wider island, begin with the Kalimantan regional guide.

How the forest plants of Kalimantan group by use

The simplest way to make sense of the forest plants of Kalimantan is to group them by what they yield. Timber, latex and fat, rattan, the plants of poor soils, and the plants dug up or stripped for roots and bark all put different pressure on a forest, and each group needs different care. That split shapes the groups that follow. Each species is placed in the group where its use matters most to a buyer or a walker.

Timber trees: ulin, keruing, tembesu and ramin

Ulin, also called Bornean ironwood, is the heaviest-duty timber on this list. Its wood is dense and very durable, and it resists termite attack. The tree grows in lowland forest on valleys, hillsides and low ridges, usually below about 650 metres, and commercially exploitable trees reach around 30 metres. Ulin has long been used for foundations, bridges, roof shingles and the posts of riverbank houses, so it is still a working timber rather than a museum species. Demand for the timber has depleted wild stocks, and slow regrowth makes recovery difficult, which is why it is listed as Vulnerable. For a closer look at its uses, see ulin ironwood.

Keruing is the trade name for timber from several species of Dipterocarpus, a genus of tall trees in the dipterocarp family. Dipterocarps are among the largest and most valuable trees in Southeast Asian tropical forests, and several of them give timber sold under the single name keruing. The same genus gives a resinous oil that the trade sells under names such as gurjun and keruing oil. Keruing is sold as timber under that trade name, and recognising the wood is the practical skill, which keruing explains.

Tembesu is an evergreen hardwood tree of Southeast Asian forests, with an irregular crown rather than a neat one. Knowing its name matters when you read timber labels, because the names of the dense hardwoods overlap in everyday trade, and a seller may use a local name for a wood you would otherwise not connect to this tree. For what to expect from the tree itself, see tembesu tree.

Ramin is a swamp timber from the lowland forests of Borneo, Sumatra, the Malay Peninsula and Singapore. Past heavy extraction has reduced its wild populations, and the species is now listed as Critically Endangered. Trade in ramin is restricted under international rules, so anyone buying a ramin product should ask where and how the wood was obtained. The trade limits are explained further in ramin wood in Indonesia.

Latex, gum and fat producers: jelutung, jelutong, nyatoh and tengkawang

Jelutung and jelutong are two spellings for the same family of latex trees, Dyera, which has a hill species and a swamp species. The hill tree grows to about 60 metres and can be found across Borneo, Sumatra, Peninsular Malaysia and southern Thailand. In the early twentieth century jelutong was made into a cheap rubber that was good enough where elasticity mattered little, and the tree’s latex then became a chewing gum base. In 1922 American demand rose sharply because supplies of chicle were shrinking, and jelutong’s lack of taste and steady consistency made it a usable substitute. Its gum role lasted through the 1960s.

The same tree also shows the cost of tapping. Prolonged tapping kills it, and high yields often shorten its life, so the way a tree is cut matters more than the volume it gives. Jelutung latex tree covers the tree as a rubber alternative in Kalimantan’s forests, while jelutong latex tree looks at the same genus across Borneo and Sumatra. Read both if you are trying to pin down a product’s origin, since the names are used interchangeably in trade.

Nyatoh is the gutta-percha tree of Borneo and Sumatra. Its latex belongs to the same group of forest gums as jelutung, and nyatoh tree explains how the two groups differ in use.

Tengkawang is the common name for Shorea trees whose nuts give a hard fat. Trees fruit heavily only every few years, and harvests in Kalimantan usually come in the monsoon season, roughly December to February. Dayak communities gathered the fallen nuts, dried them in the sun, pounded or crushed the kernels, heated them and pressed out the oil, which then hardens into butter. The fat is a cocoa butter equivalent, close enough to cocoa butter that it is used in chocolate, and it has been used for cooking, for oil lamps and for candles and soap. Several tengkawang species are listed on the IUCN Red List, and the main species are protected by law across much of Indonesia. Logging is banned in most regions, but the timber is still cut, which is why tengkawang butter covers the fat and the tree together.

Rattan, climbers and basketry: rattan, bajakah and Dayak basketry

Rattan is a climbing palm, not a woody vine. Its long stems are stripped of their leaf sheaths and used as cane. The whole cane serves for furniture frames, while the split or peeled cane makes matting and basketry. Only a minority of rattan species have commercial value, and most of the cane traded internationally still comes from wild stands. Cultivation is growing through agroforestry and shifting-cultivation fields, and in Borneo work from 1983 on rattan in traditional swidden systems treats the crop as part of cultivated fields rather than a separate plantation. Many commercial plantations in the region are linked to rubber. The harvest and trade are set out in detail at rattan cane.

Indigenous use of rattan runs from simple baskets to fish traps, and the plaiting skill is as much a part of the plant’s value as the cane itself. Plaited baskets and mats still made from it are described in Dayak rattan basketry. Bajakah is a different kind of climber, a medicinal vine of the island’s forests that bajakah vine treats in its own right. It is a reminder that the forest canopy holds more than timber and cane.

Carnivorous plants, orchids and heath forest: pitcher plants and kerangas

Pitcher plants form their traps at the end of a long midrib, or tendril. Most plants carry two kinds of pitcher, larger ones low down and smaller, differently coloured ones higher up, and each has a lid and a slippery rim that help trap prey. Borneo is one of the island centres of the genus. Lowland species need warm conditions all the time, while highland species need warm days and much cooler nights, and the dividing line between the two groups falls roughly at 1,200 metres. Many of the species are threatened, and all are listed under CITES, with two species in the stricter appendix. Which species to look for at each altitude is set out in pitcher plants of Borneo.

Wild pitcher plants also turn up in lowland heath. Fieldwork in heath forest and roadside habitat around Tanjung Selor in North Kalimantan found six wild species and one natural hybrid, and it found the threats were highest where forest was cleared for farms and other uses. That point links directly to kerangas heath forest, which grows on acidic, sandy and very nutrient-poor soils.

Orchids make up another large part of the flora. Borneo holds a substantial orchid flora, and many species grow on trunks and branches high in the canopy rather than in the soil. The main orchid groups, and what a walker can realistically expect to see, are the subject of Kalimantan orchids.

Roots, bulbs and aromatic trees: pasak bumi, tongkat ali, bawang dayak and Borneo camphor

Pasak bumi and tongkat ali are two common names attached to Eurycoma, a small tree of the lowland forest understorey in Borneo and Sumatra. Its roots are boiled and the liquid taken as a tonic in traditional medicine, and the plant is found across a wider region than the island alone. Harvesting the wild plant uproots the whole specimen, which is why Malaysia restricts harvest of wild trees and bans raw export. Keep the harvest question in mind when reading about pasak bumi and tongkat ali, since the plant’s sustainability is the main practical issue.

Bawang dayak is the name given to a bulbous plant of the genus Eleutherine, and the name translates roughly as Dayak onion. It is a plant of the island’s traditional use rather than a crop, and preparation and growing areas for bawang dayak are the details to check.

Borneo camphor is Dryobalanops aromatica, a tall emergent tree found in Sumatra, Peninsular Malaysia and Borneo. It was one of the main producers of camphor, and the aromatic crystals were valuable enough to draw early Arab traders to Borneo, where they were used in incense and perfumes. The trade in Kapur Barus camphor, named for the Sumatran port of Barus, is part of the same story. Its wood is a heavy hardwood sold under the name kapur, and the species is listed as Vulnerable. History and timber are covered together in Borneo camphor.

Telling these forest plants apart by habitat

Most people meet forest plants in the order the landscape gives them, not in the order a checklist does. Heath forest on acidic, sandy soil is where kerangas and its pitcher plants grow, and it is a different world from the lowland dipterocarp forest on riverbanks and ridges, where ulin, keruing, tengkawang and rattan are most at home. Swamp forest holds ramin and the swamp species of jelutung. The highlands change the picture again, because pitcher plant species shift with altitude and the cooler nights above roughly 1,200 metres suit a different set of plants.

If you are trying to decide which group to focus on, start with the thing you want to understand. A timber buyer should read the timber sections first, and a traveller interested in wild plants should study the habitats before walking a trail. Moving between the groups is mostly a matter of moving between habitats. A river journey crosses riverbank timber trees, swamp species and rattan-climbed edges, and a walk on heath or roadside ground can bring you to pitcher plants that would be absent from the forest beside it.

The useful question for any species is where it grows, not whether it is valuable. A tree that is common in one kind of forest may be rare in another, and a plant that thrives on roadside disturbance may be squeezed out by the same clearing that opens up a trail. Check each species’ habitat before deciding where to look for it.

Sustainability limits that apply across the list

Almost every species on this list is under some form of pressure, and the limits differ from one to the next. The table lists the main status for each group and the practical step that follows from it.

None of these limits is a reason to avoid the plants altogether. They are reasons to ask questions before buying and to leave wild plants where they grow. A short conversation about origin with a seller will tell you more than any label.

Practical notes for visitors and buyers

Stay on marked trails in protected areas, since many of the species here live in small, scattered populations that a few visitors can disturb. When a shop sells timber, cane or fat, ask where it came from and whether the harvest was controlled. If a seller cannot answer, treat that as the answer.

For pitcher plants and orchids, photography is the safe choice. Digging up a pitcher or lifting an orchid from a tree removes a plant that may take years to recover, and in the case of pitcher plants it may remove a species that is already threatened. Leave wild material where it grows and buy any plant products from growers who can say where the plants were raised.

Plan visits around the seasons. Tengkawang nuts are harvested in the monsoon months, roughly December to February, so a visit timed to that season is the one most likely to see the work of collecting and processing the fat. For regional routes and the towns that serve these forests, the wider Kalimantan guide is the place to start.