The queen palm tree (Syagrus romanzoffiana) earns its regal name with a mature height of 50 feet and long, lacy fronds that easily reach 10 feet long. Growing in U.S. Department of Agriculture plant hardiness zones 9 through 11, queen palm suffers severe damage at 25 degrees Fahrenheit and it may die if temperatures reach 20 F. Queen palm might grow well in colder climates, but it must be protected from freezing temperatures.
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Cover the Terminal Bud
The terminal bud is the point from which all new growth originates and is the most important part of the queen palm tree to protect in a freeze. This bud is at the very top, center of the tree where the new fronds open. The best option for protection is to completely cover the tree from top to bottom with burlap, old blankets or frost cloth, trapping warm air in around the tree. The cloth should not touch the tree, so drive stakes in the ground that are slightly taller than the tree and drape the cloth over the stakes. This method is only practical with young, small queen palms. For taller, mature palm trees, you can drape the cloth over the fronds, tying it in place under the canopy.
Protecting the Trunk
The palm's trunk needs to be kept warm if the tree is to survive. Frost cloth is an insulating material designed specifically to protect plants against frost, but practically any warm, insulating material works. Try wrapping the trunk with several layers of blankets -- moving blankets work well if you don't want to strip your bed linens. Burlap, fleece and other fabrics can also be wrapped around the tree. If you don't have blankets or fabric to spare, you can use several layers of fallen palm fronds to insulate the trunk. Tie the material on the trunk loosely and remove it when the temperatures rise. Outdoor strand lights emit a small amount of heat from the tiny bulbs and can help keep the trunk warm if you wrap several strands close together around the trunk.
Insulating the Roots
Queen palm roots get some insulation from the soil, but a hard freeze can freeze the ground and roots. A layer of mulch roughly 6 inches deep helps insulate the ground to protect the roots from frost damage. If you've ever reached your hand to the center of a mulch or compost pile, you'll have noticed that the decomposing materials are warmer than the material on the outside of the pile. Shredded bark mulch is the most obvious choice, but any organic material can be used as mulch, including leaf mold, dried glass clippings or straw. Whichever mulch you use, keep the mulch a few inches away from the queen palm's trunk. Before the freeze occurs, water the queen palms roots by thoroughly saturating the planting site. The water helps in insulating the roots and keeping them warm so they're better protected from freezing temperatures affecting the soil.
Frost Protection Sprays
Freezing temperatures draw the moisture out of leaves -- a process known as transpiration -- and the moisture freezes on the leaf surfaces. Frost protection sprays, also known as anti-transpirants, are designed to coat the leaves to prevent moisture from transpiring during freezing weather. These sprays can increase a queen palm's cold tolerance by as much as 9 F. Spray a generous coat of a frost protection spray on all the queen palm fronds. Application instructions and how long the spray is effective vary among products, but you can generally expect a single application to protect the queen palm for one month. While the spray protects the leaves and can be used on the terminal bud, it does nothing for the roots and trunk, so you'll still need to protect those.