Though Tennessee is not a big producer of commercial citrus, it is possible to grow citrus in a home landscape, both in the ground and in pots. The state is in U.S. Department of Agriculture Plant Hardiness Zones 6 and 7, and citrus trees are best grown in the warmer part of the state, as they need ample heat to produce sugars and cannot tolerate frost.
The best choices for Tennessee are cold-hardy varieties, and even these should be planted in pots or where there is some protection. Lemons, limes, sweet oranges and grapefruit are not good selections for Tennessee, as they are particularly susceptible to frost.
This small tree produces easy-to-peel tangerine-sized oranges that are similar to satsumas, thought not as sweet. Trees are hardy to 5 degrees Fahrenheit. An old variety that originated in China, "Changsha" (C. reticulata) produces a heavy harvest once established and bears fruit in fall and early winter. This tree is best planted in Zone 7 in Tennessee.
This hybrid is a tough, thorny tree that produces large orange fruit that is similar in taste and size to grapefruit. Trees are hardy to 0 degrees and may be planted throughout Tennessee, though they should be planted in protected areas in Zone 6. Originally believed to be from the Nansho district in Taiwan, Nansho (C. taiwanica) trees produce fruit in winter.
The hardiest of orange trees, the trifoliate orange (C. trifoliata) can withstand temperatures down to -20 degrees, and may be planted throughout Tennessee. Trifoliate trees are very thorny and, unlike most other citrus trees, are deciduous. This tree is ornamental, as fruit is sour and considered inedible. Other than for decoration, it is used for rootstock for other citrus.
Trifoliate orange trees may be used as a windbreak or barrier, and have curvy, twisted branches.
This mandarin hybrid is a commercial tree in Japan and occurs naturally. The "Yuzu" (C. ichangensis x C. reticulata) produces a medium-sized yellow or green fruit with lots of seeds that is sweet but lemony in flavor. The tree is hardy to 0 degrees and may be planted throughout Tennessee. The "Yuzu" is a bit more shrub-like than most citrus trees, and fruit ripens in fall to early winter.