Answer: Since avocado trees bloom during the winter time, frost poses more of a problem with fruit set than with the overall health of the trees. However, there are other considerations for very young trees:
Wrap the trunk of new trees with heavy paper, corn stalks or the special thermal wraps. If this is done to a point above the bud union, the chances are that you will have a complete budded tree when winter is over even though the exposed parts of your tree are killed.
At the onset of spring you will be able to unwrap the damaged tree and select a shoot or shoots, above the bud union, so as to renew your tree. Do not remove dead tree parts until new shoots are growing well.
An even more effective insulation to preserve the bud union is a collar filled with sawdust to a point 6 to 12 inches above the union. The collar may be 5 or 6 inches in diameter. It is almost impossible to freeze tissue within this mass of sawdust.
Foliage is more difficult to save under severe frost conditions. Any wrapping around and through it will help. Sometimes bunches of straw are intertwined with the foliage and matted around the branches to serve as an insulating mass. A suspended canvas and wood canopy above the tree will help. Under very extreme conditions, people have erected tents and placed lighted electric bulbs within the structure. Remember two things:
1. A complete enclosed covering of polyethylene or other non-breathing plastic is often worse than nothing -- especially where it touches the tree.
2. Trees do not survive well in darkness, so the tree must be allowed to see sunlight during the day.
Hope this helps you prepare your trees for exceptionally cold weather!
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