Swietenia macrophylla

Common Names: Big Leaf Mahogany/Honduran Mahogany (English), Caobo (Spanish), Nhạc ngựa (Vietnamese), 大葉桃花心木 (Chinese)
Scientific Name: Swietenia macrophylla King
Family: Meliaceae
Natural Distribution: Southern Mexico, Belize, Guatemala, El Salvador, Honduras, Costa Rica, Nicaragua, Panama, Dominica, Colombia, Ecuador, Venezuela, Peruvian Amazon, Lowland Bolivia, Brazilian Amazon and possibly The Guianas and other Caribbean Islands.
Natural Habitat: Occur in tropical rainforests up to 1,500m in altitude.
IUCN Red List: Vulnerable
Description: An evergreen tree (sheds leaves when spring comes and quickly grows back leaves) that can grow to 40m high and at least 1m in diameter in their natural habitat. Large specimens are buttressed. The wood inside is reddish brown. New young leaves are pinkish red and turns green when matures. Mature leaflets usually can grow to around 20cm. When leaves mature they paripinnate with even numbered leaflets (usually odd numbered when young). Leaves are smooth and mature leaflets usually grow obliquely and acuminate.
Flower: Flowering in spring. The same tree has male and female flowers (very similar visually). The panicle is roughly around 15-30cm. Flowers are small (less than 1cm), with 5 petals and are creamy green coloured.
Seeds: Often called the sky fruit as the tip of the capsule (about 10-15cm long) always points upwards and most of the time towards the sky. Once the woody capsule (fruit) matures, the samara (fruits with wing-like structures) within is dispersed by wind (rotate like a helicopter). Dehiscent capsule has 5 lobes. Fruits usually in summer. Seeds exhibit orthodox behaviour in professionally-set low temperature and low humidity storage.

National Tree of Belize. The genus Swietenia (named after a physician called Gerard van Swieten) is comprised of 3 species (might be more) and the genus is closely related to the African relative Khaya (another genus in the Meliaceae family, the genus is also comprised of species capable of producing quality timber). Swietenia fruits are hard to distinguish apart but one easy way to differentiate the species is that Swietenia macrophylla, as the name suggests (literally means big leaf), has the biggest leaf in the genus. The species is exploited for its timber, with populations dwindling in their natural distribution. Compared to Swietenia mahagoni (L.) Jacq., Swietenia macrophylla has softer wood but grows much faster. Although they are endangered, they are invasive species in some wet tropical regions that are outside of their native zone and are quite prolific. It is now a quite commonly planted tree in the tropics, especially for forestation. Even when mature, this species probably cannot tolerate temperatures lower than 5°C/41°F for an extended period of time. From what I have seen, I think the mahoganies flower and fruit more consistently in at least a subtropical climate and with at least 2,000 hours of sunshine a year. 

I find that this genus fruits best (and more consistently) in tropical climates (and in places warm enough that winters are short and still able to reach at least 21°C/70°F during the day). I have tried to germinate stored Swietenia macrophylla seeds but was unsuccessful (I did put it in the fridge for 3 months along with Khaya senegalensis and 8 out of 15 Khaya senegalensis seeds germinated while all Swietenia macrophylla seeds grew mold). So in case seeds are faulty, collect many and make sure they are fresh (if the wings are still crisp and the colour is not dark brown then the seeds are likely to be fresh).

2018/06/16, 6th day of germination. Again I germinated the seed in Sphagnum moss.