Humidity tray

A humidity tray is a shallow, wide tray filled with pebbles or gravel and a layer of water, placed under an indoor bonsai pot without letting the pot itself sit directly in the water. As the water evaporates, it raises the humidity in the air immediately around the foliage, which helps offset the dry air common in centrally heated homes.

This matters most for tropical and subtropical species kept indoors, like ficus or jade, since these trees evolved in humid environments and can struggle with the low humidity typical of an indoor room compared to an outdoor garden. A humidity tray is a low-effort way to raise local moisture without misting constantly throughout the day.

The key detail people get wrong is letting the pot sit in the water itself rather than above it on the pebbles, which can waterlog the soil and encourage root rot instead of helping the tree. Refilling the tray as water evaporates and keeping the pebble layer clean are the only real maintenance a humidity tray needs.