Dillenia indica

Common Names: Elephant Apple (English), Simpoh (Malay), चलता (Hindi), চালতা (Bengali), သပြုပင် (Burmese), มะตาด (Thai), 오아과 (Korean), 五椏果/第倫桃 (Chinese)
Scientific Name: Dillenia indica L.
Family: Dilleniaceae
Natural Distribution: Assam (India), Himalayan Foothill (Nepal, Bhutan), Northern Bangladesh, Sri Lanka, Myanmar,  Yunnan Province (China), Laos, Thailand, Vietnam, Malaysia, Singapore, Indonesia (West of Wallace’s Line)
Natural Habitat: Low elevation tropical valley and stream forests under 1,000m
Description: Monoecious evergreen tree growing up to 20-30m tall. Leaves simple, with distinctive lateral veins that look like furrows. Leaf length can exceed 30cm long. Bark flaky and reddish. Buttressed roots not prominent.
Flower: White bisexual flowers with 5 petals are produced annually from about May to September. Numerous yellow stamens surround the central styles (numerous ovules).  Flower diametre can reach 20cm. 
Seeds: Large round yellow fruit can grow to 15cm in diametre (the sepals aggregate and form the large fruit). Fruit mature during Northern Hemisphere’s winter, about December to March (or even later). Fruits can weigh more than 1kg.  Seed itself is creamy-coloured but surrounded by brownish red short hairs. The falling fruit can be hazardous if trees are tall. Large herbivores in the forest help with propagation (but not necessary). Germination usually takes 1-3 months. Seed is about 0.5cm long and are probably recalcitrant.

Dillenia indica can be easily distinguished from other tropical plants because of its distinctive leaves and fruit. It prefers a warm humid climate. If intended for consumption, the fruit (sepal part) is mixed into curry dishes or the slimy inner part (the true fruit) is made into jelly. However this tree is mainly planted for ornamental purposes in tropical and subtropical climate zones (most likely frost tender, probably cannot grow well if winter daytime regularly dips below 5°C/41°F). The fruit has a distinctive fermented scent. Its timber is probably used on a local scale. 

2018/05/19, the collected Dillenia indica fruit from 2 days ago was cut open. The outside hard-fleshy part encapsulates the inner true fruit (the foldy pulp bits). The seeds are found within those inner yellow envelope-like structures.

Fruiting season is relatively extended and as long as the fruit is not green but yellow and  starts to smell (which I would describe as a overly fermented guava and peach juice), then the fruit is probably ripe. I have found Dillenia indica fruits that contain no seeds in subtropical climate zones, and so nowadays I always try to open it as soon as possible to see if there are seeds before I take the pungent fruit home. Getting to the seed is easy but separating the seeds from each other is a real hassle. Once you get to the true fruit, you will begin to feel the sticky slime inside and the seeds are covered in this. Some people use sieves to separate the slime from seeds, some people use cloths and wash it, but whichever method, it will take some time. I usually just squeeze the seeds inside my fist and run it with water and then dry it with a hand towel or tissue. Even if there is still a little slime, it should be okay. 

2018/10/31, I found some seeds with roots. They might have germinated a week or so before this date.

When I chucked the seeds into the Sphagnum moss, I really wasn’t hoping for anything because a few years ago I have placed Dillenia inidca seeds into Sphagnum moss before and those didn’t germinate. Plus I put these seeds in the moss in winter. The temperature in the Sphagnum moss box probably has dropped to 12°C/53.6°C at its lowest (humidity always above 80%). This is my first success ever in germinating Dillenia indica and so I am not sure which factors contributed to the long germination. Perhaps the low temperature slowed the germination of the seeds; I don’t think Dillenia indica seeds behave in an orthodox manner. The humidity and the dampness in the moss box was probably why the seeds stayed alive. So it is probably a better idea to get the fruits in summer and plant the seeds at that time of year for faster germination. 

2018/11/22, Dillenia indica seedlings start to emerge out of the seed coat as the weather warms.

All the Dillenia indica seeds germinated (100%). However they do grow quite slowly. The seedlings haven’t grown true leaves until roughly 3 months later. I think this could be because they are still in the moss (no nutrients), but I still intend to leave them inside until their roots are much more established. The temperature is still not quite hot yet so I’ll have to see whether it will grow faster when the temperature rises.

2018/12/24, stored Dillenia indica seeds from 2018 May. The seeds were dry.

I still have quite some leftover stored seeds, I will one day test whether they can still germinate after being stored for a year. Little hope but I think it is a good experiment that is worth a shot. Maybe the seeds actually exhibit intermediate storage behaviour.

2019/01/22, this seedling’s true leaf bud started to enlarge 4 days ago.

The seedlings are growing taller and bigger. It does seem that the seedlings do grow faster when the temperature is high (in the past month, there were many days when the temperature exceeded 27°C/80.6°F indoors). Regardless, this is not a really fast growing tropical tree. The emergence of the true leaves is relieving, I will plant these in a pot soon.