rockm

Let the tree alone. Leave it outside until mid November. Let it get hit repeatedly by frosts--not hard freezes below 25 though. Frosts are a key part of a tree's dormancy cycle. They slow the tree down and make it drop its leaves. Once the tree's leaves have either fallen off, or have turned brown--some elms will retain dead leaves in the winter--move the tree into the garage. Bury the tree's roots--pot and all--into a box of pine bark mulch that's been well-moistened. Dormant deciduous trees need no light during dormancy. Keep the tree away from the window and sunlight, as that can warms things up too much, resulting in early bud break. Let the plant alone--save for checking every few weeks to make sure the roots remain moist--not soggy. Don't worry if the root ball freezes. As long as it stays above 20 F in the garage, the tree will be fine.

As buds begin to swell in the spring, you've got to make sure the tree doesn't come out too early. This can mean moving the plant outside in the daytime to a shaded place that remains cold, and back inside at night...