USDA climate zone 7 can get mighty cold in winter. In Oklahoma, the mercury can dip to below 5 degrees F. Even in warmer Little Rock, Arkansas, occasional temperatures of 10 degrees occur. Because the Satsuma mandarin orange can die if it’s exposed to long hours of 18-degree weather, you must protect your tree when the weather is cold. One way of ensuring that your orange tree is safe is to grow it in a large container. It will thrive outdoors from spring until fall, and then when the weather forecast is for temps in the teens, move it indoors.
Plant your semi-dwarf Satsuma orange tree in spring, using a large pot with a drainage hole. To ensure good drainage, use a light potting soil mix without peat moss. If you cannot find a mix without peat moss, add redwood shavings to equal about 1/4 of the amount of potting soil you need.
Move your tree to a sunny spot in your garden where it will receive eight hours or more of direct sun every day.
Water your Satsuma once or twice a week, but only when the potting soil is dry. If you use a plant saucer under the pot to protect a wooden deck or other area, be sure to empty it after you water your tree so the roots don’t develop root rot, which can kill a citrus tree.
Fertilize your tree with a special citrus fertilizer according to label instructions. Start fertilizing in spring when active growth starts, and repeat two or three times, at regularly spaced intervals, until fall.
Move your tree under cover, into your house or into a greenhouse before your first fall frost. Make sure that it receives adequate light, either natural sunlight or light you provide through use of a fluorescent light or grow light. Cut back on the amount of water you give your tree during winter and do not fertilize it during the colder months.