Tangerines are a type of mandarin orange (Citrus reticulata) that has thin, bright orange or blood-red skin. Mandarins are loosely divided into four groups, of which tangerines compose one. In fact, tangerines are considered the most important of the four groups, according to Julian W. Sauls, a professor and horticulturist with Texas A&M University. The trees are highly desirable for their widespread culture and usefulness in hybridization. While there are many different cultivars of tangerine trees, they all have the same basic care requirements.
Tangerine trees can vary in their cold hardiness, depending on the cultivar. In general, these trees should only be grown outdoors in United States Department of Agriculture (USDA) hardiness zones 8b through 11. Some smaller or dwarf cultivars can be grown in containers and used as specimen or patio trees. These trees can be set outside during the warm weather of spring and summer, then brought indoors during the colder fall and winter months.
Tangerine trees, like all mandarin and citrus trees, need exposure to full sunlight in order to thrive. These trees should have at least eight, but preferably 12, hours of sunlight per day. Otherwise, blooming and fruit production will be greatly reduced. When planted near a home, tangerine trees should be placed on the south or southeast side of the house, where the ground tends to remain the warmest, according to Dr. Sauls.
Established trees should be watered about twice per month. Watering should be slow and deep. Water with a drip or soaking hose for best results, and let the water run for at least a couple of hours. Newly planted trees should be watered once a week during the first growing season.
Never fertilize newly planted citrus trees. Wait until the second spring to give them any fertilizer. One cup of ammonium sulfate should be given for each year of the tree's life. Split the dose into three parts, and give one part in February, one in May and the last in September. For example, a tree that is three years old would receive one cup in late winter, one cup in the spring, and one in early fall. Mulching is not good for citrus trees, according to Dr. Sauls, as it can lead to root or foot rot.
Keep the ground around your tangerine tree clear of weeds that could compete with the tree. This includes lawn grasses. Extend this area to the edges of the tree's canopy. Protect the lower trunk of the tree by wrapping it in one layer of heavy-duty aluminum foil that is about eight inches wide. Loosely crimp the edges of the foil together and mold it to the trunk of the tree. This will prevent damage from herbicides you may be using to kill the weeds. It will also prevent sprouts from growing up along the base of the tree. Finally, protect your tree from cold weather by piling the soil around the tree in the fall (this is often called a "soil bank") and removing the pile in the spring. If your tree is small enough, you can even throw a blanket over it during times of extreme cold weather.