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Time to pick the fruits of propeller trees

April 23, 2013

Propeller trees, Dipterocarpus spp (Dipterocarpaceae), are important for the Southeast Asian forest ecosystems. Many species have a hard and durable timber, leaves for roof thatching or food packing, source of resin, excellent bark for epiphytic orchids and they are ectomycorrhizal hosts of many edible (and poisonous) mushrooms. What are the common tree species here in the Chiang Mai valley, and how do I get them?

A positive trend is that around Dokmai Garden, which develops at a tremendous speed, new land owners tend to save the native dipterocarps. The most common species in the lowlands, and in all of the province, is Dipterocarpus tuberculatus. Yesterday’s wind blew down a few fruits which I collected like a troll finding gold. The fruits are not available every year, and last time we planted many seedlings was in 2010, the worst drought in 50 years, so they all succumbed. This year we shall be prepared and even babysit (irrigate) if the drought is too severe. I love to eat mushrooms and I find this particular tree handsome, so I need to boost it in the garden. An established tree can stand droughts and fire, while seedlings are sensitive.

Another common lowland dipterocarp is Dipterocarpus obtusifolius, also growing naturally nearby Dokmai Garden. I collected a nice heap of seeds of this species too. The aim is to create an educational lowland monsoon forest.

Dipterocarpus tuberculatus and D. obtusifolius.72Left: Dipterocarpus tuberculatus leaf and fruits. Note the leaf’s heart-shaped base and fanning veins. Right: Dipterocarpus obtusifolius leaf and fruits. Note the leaf’s blunt (obtuse) tip and base, and the veins being parallel to each other.

Dipterocarpus tuberculatus seeds.72A close-up  picture of the D. tuberculatus fruits. They have two prominent wings for wind dispersal, and three remnants of wings looking like mouse ears. Between these five wings, the fruits have five ridge-like ‘tubercles’. The wings are fused and completely wrap the seed, a nut.

Dipterocarpus obtusifolius seeds.April22.2013.72A close-up picture of D. obtusifolius fruits. In this species, the ridge-like tubercles are absent. The white wormlike structure is an emerging root.

Another common dipterocarp planted in the Chiang Mai valley is Dipterocarpus alatus, the tall tree you see along the old road between Chiang Mai and Lamphun. That species has fruits with ridges from top to bottom and such fruits should also be collected now. Many governmental forest nurseries provide D. alatus seedlings, but I have never seen the other two dipterocarps offered. Based on our experience here at Dokmai Garden I think that is due to the amazing growth speed of D. alatus, even when left without water. The timber of D. obtusifolius is considered inferior to that of the other two species, but for leaf litter designers its coppery and densely corrugated leaves are a delight.

At higher elevations there are other dipterocarp species, and in wetter habitats such as Borneo is the heart of Dipterocarpus biodiversity with 40 of the world’s ca 70 species. The name was coined by Karl Friedrich von Gärtner (1772-1850) in 1805. He was a German physician and botanist focused on plant reproduction and published ‘Dipterocarpus‘ in a supplement (Supplementum carpologiae) to his father Joseph Gärtner’s magnum opus De Fructibus et Seminibus Plantarum, first volume published in 1788.

Text & Photo: Eric Danell

(Precipitation report: thunder and clouds, a few drops of rain, but nothing measurable (i.e. over 0.5 mm) so keep watering demanding plants!).

4 Comments leave one →
  1. April 23, 2013 9:51 AM

    I hope our readers take up the challenge as collecting the big seeds of the Dipterocarp family is easy and fun.
    As well as Dipterocarpus we also have several Shorea and one Hopea species which are local in Chiang Mai.
    The two D. tuberculatus & D. obtusifolius produce seed earlier in the season than the stream hugging D. turbinatus, due in May and Hopea odorata ( Takien ) which is just starting to drop seed now, although some may be dropping prematurely judging from the smallness of the seed.
    D. alatus seed is easy to collect because of the huge number of trees planted, however we have no evidence that this species is native in Chiang Mai, Lamphun, Lampang and Nan nor in the northern parts of Phrae across the hills south of Phrae town. There is a long tradition, going back to the time when the Khmers were strong in the region, of planting D. alatus in temples, which is one reason why we see them around.
    At Chiang Dao there is a huge stand of D. turbinatus, known locally as Yang Daeng and I would encourage people to collect and grow these beautiful trees in preference to D. alatus. They are sensitive to drying out in the first couple of years so providing some shade and frequent watering is recommended.
    In a good year at a moist site the big seeds can be planted directly in the shade under a tree and prosper. I have done so under Longan trees and also at Huai Teng Tao, but in the latter case the 50 year drought killed them after2-3 years happy growth.
    I would also like to put in a word for Shorea roxburghii ( Payom ) a tree with beautiful yellow/cream flowers common at the foot of Doi Suthep, CMU, Wat Umong aras.

    Once seed is collected keep it in the cool and do not let it dry out. With enough moisture you will notice the big root shoot. This is the time to plant the seed and the wings having done their job of dispersal can be discarded.

    • April 23, 2013 9:57 AM

      Dipterocarpus alatus is claimed to be native to India and Bangladesh as well, do you think this is true or are they planted?

      • April 23, 2013 12:02 PM

        The centre of diversity of the Dipterocarps is in Borneo which once was connected by land to Indochine. D. alatus is found in maritime localities e.g. Koh Samet & Koh Samui and may well have spread naturally around the coast across Burma to the Indian sub-continent. It appears their spread has been restricted northwards to the Lanna area by the steep mountains and narrow ravines. Simon Gardner reports its presence in Payao which is in the less steep Mekong watershed.

  2. Ghani Chong permalink
    October 4, 2015 7:30 PM

    Hi, thank you for the great website! Yes, collecting seeds from the forest is great fun. We are having a mast year as of now in my hometown of Beaufort, Sabah. Easiest way to finding different types of fruits is, i find, along river sides(both side of the river). If one like a challenge then follow a small stream and trek uphill so we do not get lost! You will be pleasently surprised by what hard to find tree species are hidden in those hilly slopes! At the moment i am busy collecting Shorea seeds of leprosula, fallax, singkawang, macroptera, curtisii and many others i hope to sort out later! No time to ponder so many seeds to plant, backach! Have a nice day everyone, cheers!

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