A lemon tree's lack of cold tolerance is one of the primary factors that determine where the tree can be grown successfully. In most parts of Alabama, winter temperatures are simply too cold to allow gardeners to plant lemon trees in-ground in their gardens. In the warmest parts of the state, however, the most cold-hardy types of lemon may be able to survive the winter outside if given adequate protection. Elsewhere in the state, growing trees in movable containers is an alternative.
Lemons and Hardiness Zones
Lemons (Citrus limon) are generally hardy only in U.S. Department of Agriculture plant hardiness zones 9a through 11, and they may die if exposed to temperatures below 30 degrees Fahrenheit.
In Alabama, the climate ranges from USDA zone 7 in the northern part of the state, north of Tuscaloosa, to zone 8 in most of the rest of the state. Only a very small part of extreme southern Alabama, the coastal area south of Mobile, falls into USDA zone 9a. In this zone, the average minimum temperature ranges between 20 and 25 degrees Fahrenheit, so growing lemon trees outside is risky even here.
Varieties for Alabama
The most cold-hardy type of lemon is a hybrid, the Meyer lemon (Citrus x meyeri), and it's the variety most likely to be able to withstand winters in south Alabama. Meyer lemon is, like other types of lemon, reliably hardy in USDA zones 9 through 11, but it is more tolerant of cold temperatures than most other varieties and will fare better when temperatures are near freezing.
Other varieties of true lemons, such as 'Lisbon' (Citrus limon 'Lisbon') and 'Eureka' (Citrus limon 'Eureka'), can also be successfully grown in Alabama, including the northern parts of the state, provided they're grown in containers and taken inside when temperatures fall.
Protection From Cold
Lemons grow best when daytime temperatures are in the 70s and nighttime temperatures remain in the high 50s. When temperatures fall into the low 50s, trees may go dormant and stop growing, and when temperatures fall into the 40s, injury to the tree is a possibility.
To protect an in-ground tree less than 5 years old from winter cold, pile soil around the trunk to a height of 15 inches in the fall, and remove the soil as soon as freeze danger has passed in the spring. A polypropylene cover over the tree's canopy can also help to protect leaves from freezing temperatures.
To shield container-grown trees from cold temperatures, bring them indoors and place them near a sunny window when temperatures fall to 40 degrees F.