Because lemon trees (Citrus limon) require protection from frosts, in many areas, growing them in pots is the only option. Lemons grow outdoors year-round in U.S. Department of Agriculture plant hardiness zones 9 through 11.
Lemon trees planted in pots seldom reach the same size as they would The size of the pot ultimately determines how large your lemon will grow. Dwarf varieties are a smart choice for pots because they generally stay under 6 feet tall.
Planting Your Lemon Tree
Select a container the next pot size larger than the one the tree came in. For example, a tree in a 12-inch-diameter pot should be transplanted into a 14-inch pot. Pots that are too large make controlling moisture more difficult and may invite root rot. Whatever container you use, make sure it has drainage holes in the bottom.
The potting mix you use should be light and well-draining, without any added fertilizer. A commercial cactus or citrus mix works well.
Add some potting mix to the container while leaving space for the root ball of the lemon tree. The pot should have enough soil so that when the root ball of the tree is planted, it will be at the same height as it is in the nursery container.
Tap the sides of the container to loosen it from the root ball. Slide the root ball out by laying the container on its side and slowly and gently pulling the plant out by the trunk.
With your fingers, gently wiggle loose any roots that have become entwined around the root ball.
Place the tree, centering its trunk, inside the container on top of the soil. Add or remove soil as needed so the tree is at the same level in the new pot as it was in its original container.
Fill in around the root ball with the potting mix. The tops of the roots should be just beneath the soil surface. Do not cover the trunk with soil or bury it deeper than it already was.
Tamp the soil down inside the container firmly with your hands.
Water the container thoroughly, until the water drains freely from the bottom.
Maintaining a Potted Lemon Tree
Place your lemon tree in a sheltered area that receives at least six hours of sun. In most climates, a southern exposure provides the warmth a container-grown lemon tree requires. In hot-summer climates, place it where it will get some shade in the afternoon.
Lemon trees, like all citrus, love nitrogen. Feed your tree during the growing season by using an organic fertilizer formulated for citrus trees. As a general guideline, use 3 tablespoons of 7-3-3 fertilizer for every 8 inches of pot diameter monthly, starting in February. Always follow the labels' instructions. Water the plant after applying the fertilizer.
Lemon trees require deep and infrequent watering. How often depends on weather, wind and other factors, such as the soil mix used and the kind of pot it is planted in. In general, water once or twice a week, saturating the soil until the water drains out of the bottom of the pot. The top of the soil can be dry in between watering.
A wilted tree that recovers after watering signals a lack of moisture. During particularly hot or windy conditions your lemon tree may require more water, and less when the weather is cool or rainy. In hot weather, check the soil daily.
When tree roots begin to grow through the pots' drainage holes, it is time to re-pot in a larger container.
Protection From Frost
To avoid severe damage or death from freezing, lemon trees must be protected from temperatures 32 degrees Fahrenheit and lower. Potted plants are even more susceptible to extreme temperatures than ones planted in the ground. In cold winter climates, moving the pot into a bright spot indoors is one solution.
If your tree stays outside when expecting a frost or freeze, harvest any ripe lemons and water the tree well. Moist soil retains more heat than dry soil. Move the pot to a protected area, such as a covered patio or porch next to the house.
Cover the tree with burlap, sheets, blankets or frost covers. Don't use plastic because it can damage the tree. Remove the covering during the day when temperatures rise above freezing and replace it over the tree before sunset. Frost covers, made of breathable fabric, are the exception, and may be left on the tree all day for several days at a time. Depending on their weight, they can provide 4 to 8 F of frost protection.
Lemon Tree Pests
Ants around your lemon tree likely indicate a problem with aphids. If you spot these, scale insects or mites, use insecticidal soap. Following all label instructions, mix 5 tablespoons with 1 gallon of water and pour it into a sprayer. Spray the affected areas and undersides of leaves at weekly intervals as needed. Do not apply during windy conditions or when temperatures exceed 90 F. Wear long sleeves, long pants, gloves and protective eyewear when working with insecticidal soap.