Things You'll Need
Christmas tree lights
Hose with sprinkler attachment
2 by 2 boards
Frost protection fleece
The windmill palm (Trachycarpus fortunei) is hardy in cold weather as low as 5 degrees Fahrenheit, so if you are growing one in a temperate climate zone it might survive the winter without your help. But to be on the safe side, it's wise to protect your tree in winter if it is growing in the ground outdoors. If it's growing in a pot, you might be able to move it to a protected spot, or into your house or greenhouse for the winter if it's not too large or heavy.
Prepare your windmill palm tree for below freezing weather in late fall or early winter. String Christmas lights or one or two incandescent lights throughout your tree early in the season to spare yourself the task at the last minute when cold weather is forecast. At sunset on cold nights, turn the lights on: they will generate enough warmth to help protect your tree through the night.
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Spray your windmill palm with an anti-transpirant before extremely cold weather arrives. This product helps plants to retain fluids, preventing the dehydration that freezing temperatures cause. Apply according to package instructions; you might need to spray it at several intervals during the winter.
Set a lawn sprinkler under your windmill palm tree before cold weather arrives. On nights when freezing is predicted, turn the sprinkler on at sunset and allow it to run all night because the moving water doesn't freeze.
Build a frost frame of 2-by-2 boards large enough to completely cover your windmill palm. Then drape clear plastic sheeting, a tarp, blanket or special fleece over the frame. Remove tarps, blankets and fleece when the temperature rises; you can leave clear plastic over your tree all winter when you support it with a frost frame.
Wrap the trunk of large windmill palms in burlap or blankets and tie the fabric onto the tree with rope. Wrap your tree in fall and remove the material in spring.
Running a sprinkler all night can run up your water bill, but it’s an easy way to prevent damage to your windmill palm. Keeping your palm well watered through the winter will help it to withstand freezing weather.
Do not allow plastic, tarp or a blanket to touch any part of your windmill palm because frost or snow can damage any foliage that it touches.