Japanese maples in Southern Florida and Southern California usually fail to thrive, because they do not get a sufficiently cold dormant rest. Japanese maples need a cool to cold dormancy in winter to thrive. Maples in northern Florida & Georgia do drop their leaves and go dormant for the winter. They would have to be protected, preferably from temperatures below 0 F. Japanese maples and trident maples, the most common maples used for bonsai will not survive a northern Wisconsin zone 3b or 4a winter. The native sugar maple has leaves that do not reduce enough to be in proportion for bonsai, even though it is hardy enough. Leaves are green until autumn, then they light up in colors of gold, orange and flaming red, often all 3 colors on the same tree. Amur maple has small leaves, similar to trident maple. You can leave it outside all winter, simply set the pot on the ground, in a location that is in the shade, like the north side of the house, or a fence, or under the bonsai bench. This is the species of maple you want for northern Wisconsin. There is one species of maple good for bonsai that will survive zone 3b winters, and that is Acer ginnala, the Amur maple. That is -42 C without factoring in windchill. One night the real temperature dipped to -44 F, without wind chill. During that week the daytime highs were well below zero.

I was working for a week as a consultant at the now defunct Lake States Paper Mill in Rhinelander, Wisc.

Japanese maple bonsai indoor