Bonsai and the chill factor

Beautiful snowscape this month. Snow has covered the ground and forms small mounts of snow on the trees, giving this special winter feeling we rarely see anymore. Seems to last the month out, and lighten up the day.

If it is cold? Oh yes. Winds blowing, freezing fingers and making cheeks and noses glow red. If feels really cold when windy, but trees don’t care. The chill factor on a windy day may be high for humans but trees aren’t affected at all by this.

Bonsai in the cold

Studies from Michigan University shows wind chill doesn’t really matter to a plant.

“If the wind blows hard it cannot cool down the plant any colder than the air temperature. If the plant gets colder than the air temperature, the warmer air will warm the plant. … If conditions are windy, then the plant will only get a little warmer than the air as heat is carried away more quickly.” Source: Michigan University.
But it can dry out a bonsai when frozen. There is a little transpiration going on, even at deciduous trees during winter. And a frozen soil will not allow the roots to drag up any water. At the same time roots on trees dislikes being frozen for a longer period. Most of them are not adapted to cope with that, with exceptions of mountain trees like Pinus mugo, Pinus sylvestris, and the Japanese White pine for example.
Roots are normally in the ground where freezing rarely occur, isolated by the ground layer of leaves, mulch, or mosses and heated from the deeper ground below. The temperature differences above ground and below ground level can be very dramatic. So be aware of protecting bonsai in pots from undercooling the roots too much.


The nice weather invited for a photo shoot outside, and you can see the trees arranged for this in a slow video below. Adding a peaceful atmosphere.
After that, the trees went inside again, but do benefit from a few days outside hardening off.

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