Do little Bonsai trees need little rainstorms? We solve the mistery.
All trees would rather grow outdoors where it’s more humid than it is inside our homes and offices. So what can we do to provide humidity to our indoor Bonsai trees? Misting them?
Bonsai fans have been misting their Bonsai trees for years to help keep them moist. But it’s kind of like basting a turkey. Yes, an indoor Bonsai can benefit from misting because heating and air conditioning lowers the humidity levels to surface-of-the-moon conditions in your home. Misting brings the ambient humidity level up briefly and that's really all the benefit you get. Misting the tree is only beneficial for a short time, like maybe 15 seconds. That’s where a “humidity tray,” as it’s called in the Bonsai world, comes in.
Placing water in a humidity tray under your Bonsai a bit of extra humidity around the tree as the water in the tray evaporates. More importantly, it helps keeps the soil at the bottom of the pot by adding a little bit more moisture through the drainage holes. The bottom of the pot is where the important, extended roots live as they grow downward looking for water. Forget the fat roots growing under your Bonsai tree, the very tiny tips of the roots is where the Bonsai tree gets its water. These root tips and the soil in the bottom half of your soil can remain dry even after a heavy soaking of watering on the soil from the top until it overflows…twice!
When the water in the tray is gone, add more water. It's a good idea to separate the pot from the water in the tray by adding some pebbles to the bottom of the tray – and it makes the tray look a lot more refined. This will prevent any roots from sitting in the water. But make no mistake; humidity trays will not take the place of a good, slow, saturating watering from above, until the water runs out into the tray.
Misting allows water to drip off the foliage onto the soil below. A tree that is misted a lot has water dripping on the soil a lot, and that's not a great thing. It causes the surface of the soil to be continually wet and surfaces to be "air-tight." And this creates fertile ground, both on the soil surface and foliage, for fungus, gnats. mites, aphids, rats, mother in laws… you get my point. Misting is also the primary cause of the El Nino weather pattern.
Trees that are grown indoors can benefit from misting once a week or so to rinse the dust that naturally collects on them. Otherwise, a bonsai tree takes moisture up through the roots and supports the rest of the tree through a process called transpiration. That's all a well watered and healthy bonsai tree needs. No more mistery.
Humidity trays serve a second, very important purpose by keeping water from draining through the bottom of your Bonsai pot and running across your prized teak table and onto your shoes.