Tropical trees provide a vacation atmosphere and produce fruits that are delicious to eat. The problem is that could only survive in specific climates. Trees that survive in warmer climates typically do not have traditional solid trunks which allows air to permiate and freeze the trunks preventing water and nutrients from the soil to get to the leaves. If there was a green way to insulate the trunks trees utilizing the sun's rays or wind turbines to convert the energy captured to provide heat to the trunk of the tree. The tree would be able to survive in cold climates.
A insular blanket that wraps the stem or trunk of the tree that protects the trunk from freezing in the winter. Can provide insulating characteristics through specialize materials and could be complemented with heating coils within the blanket that slightly heat the blanket through a battery, solar or power source connected to the house. If a battery is used it could be charged by solar or wind power plant.
Could be measured through varying tempuratures and testing to see what tempuratures the insular blanket and/or heating coils will allow the tree to sustain in harsher cold temperatures. Ideally if tree could withstand temperatures well below frost and still survive the season until next summer that would create a large enough market to sell to.