Mandarin tree
This potted mandarin tree can withstand colder temperatures than some other citrus varieties.
Citrus plants are ideal adornments for South Carolina patios and porches, with their handsome evergreen foliage and fragrant flowers. Lemon and lime trees, even kumquats and tangerines, make excellent container plants and perform admirably in the warmer months. But getting them to survive the winter and produce quality fruit can be challenging. Nothing will kill a citrus tree faster than going from 70 degrees to below freezing in 24 to 48 hours—and that can certainly happen in a South Carolina winter. A few tips can help your container citrus plants survive the winter and be productive next year.
Select a cold-tolerant variety. Meyer lemon is generally considered the most cold-tolerant lemon, and it is fairly common in garden centers. In coastal areas, Meyer may survive outside all winter if planted in the ground, but in a container it will need protection statewide. Kumquat and mandarin orange varieties with even greater cold hardiness are available from specialty nurseries.
Feed and water during growing season. Container-grown citrus plants require lots of water and fertilizer. Fertilize in early spring with a slow-release citrus fertilizer, then every other week during the summer with a liquid fertilizer like fish emulsion. In the heat of summer, plants need frequent watering. Allowing them to wilt will cause fruit drop. Be careful, however, not to let the container become waterlogged.
To improve winter hardiness, stop fertilizing after July. Reduce watering as temperatures cool.
Transition plants to cooler temperatures. Prepare to move your plants into a protected location in the fall once nighttime temperatures fall into the lower 40s (Fahrenheit). Citrus, being evergreen, requires high light levels even in the winter. Indoor lighting does not come close to the quality of the sun’s rays, so leave plants outside as long as possible. Several weeks before you expect the first freeze, start reducing light levels by moving the plant into increasingly shady locations. It is normal for some leaves to drop, as the plant cannot support as many evergreen leaves at lower light levels.
An unheated garage or similar location will be sufficient protection for most of the winter. But more protection, like a heated room, will be necessary when temperatures fall below 25 degrees.
Move to the heat. Don’t be afraid to move your plant back outside during prolonged warm spells. To make moving heavy potted plants in and out less of a chore, put them on casters or a dolly so you can roll them from one location to another.
If the plant is too big to move and temperatures are not too low, you can cover it with a drop cloth (not plastic) and place a spotlight with an incandescent bulb underneath or drape it with non-LED Christmas lights. This will provide several degrees of cold protection, but make sure you remove the covering once the temperature warms.
Success with citrus can be a little more challenging than with other potted plants, but a glass of homegrown lemonade is worth the effort in the end.
S. CORY TANNER is an area horticulture agent and Master Gardener coordinator for Clemson Extension based in Greenville County. Contact him at shannt@clemson.edu.