In most pictures on Season Spotter, the only evergreen trees you see have needle leaves. These trees keep their needles year-round and add new ones in a seasonal flush. However, evergreen broad-leaf trees in the tropics often show more complex behaviour.
Unlike needle-leaf trees, broad-leaf evergreen trees often show multiple asynchronous growth phases on the same tree. In short, the tree doesn’t behave as one synchronized organism. Instead, flowering and leaf fall happens haphazardly, often in a branch-by-branch fashion. Partial blooming, fruit, and leaf development are common among tropical species and obviously hard to classify as a discrete event.
Below you see a picture I took near the Congo river in Yangambi in the Democratic Republic of the Congo. It shows a tree displaying three different leaf development stages. The dull green leaves are old, the bright green leaves are newly formed, and the yellow-red ‘leaves’ are either very young leaves or fruit (Sadly, I did not take any close up pictures or determined the species).
Although tropical trees often show this complex behavior, the phenology still depends on the tree’s environmental growing conditions. In the tropics, these conditions are mostly controlled by the amount of soil moisture and or available sunlight. Tropical tree phenology is much less well understood than that of temperate trees. It is also more complicated. But we will need to understand it in order to understand the effects of climate change on the world’s great tropical forests.