Dwarf or miniature citrus trees are ideal for container growing. Gardeners in cold regions can grow potted or container citrus--moving the container in and out of doors depending on the season--and subtropical growers can keep the tree outside all the time. Always grow in a container with drainage holes so your citrus tree doesn't have standing water near the roots.
Container citrus trees need full sun exposure in order to bear fruit. During warm months, move container citrus trees outdoors to a full sun location. When temperatures fall to 40 degrees Fahrenheit, keep container citrus indoors in a south-facing window or supplement the light with a fluorescent plant light.
Container citrus need annual pruning for shaping, air circulation and plant health. While an indoor tree can be pruned any time, the best time to prune is after you harvest all citrus fruit in the late winter. When pruning, remove suckers that grow out of the tree's trunk or out of old pruning sites. Then trim off broken, damaged or dead branches (which will be scarred or will feel hollow). Clip off branches that crisscross other growth or that grow vertically upward, since these shade lower branches.
Trees grown in containers require more watering than those grown in the ground, but too much water can cause root rot. Most container citrus treed need watering one to two times per week. Four Winds Growers suggests using a moisture meter to measure the water content near the roots, or you can check the moisture content by sticking a pencil into the soil. If dirt clings to the pencil tip, hold off on watering. If no dirt clings to the pencil, water until the soil becomes saturated. Water until you see water flow out of the container's drainage holes.
Container-grown citrus trees left outdoors in subtropical climates may require winter care during cold spells. While gardeners can carry the container tree into a garage, this may be impractical for heavy containers. To protect a citrus tree during a cold spell, string Christmas lights from the branches. Plug in the lights on cold nights to keep the branches warm. Cover the entire container tree with burlap, pinning the burlap together with pins.
Four Winds Growers recommends using a 2-1-1 N-P-K fertilizer, or one that provides two parts nitrogen (N) and one part each of phosphorous (P) and potassium (K). Apply a suitable fertilizer by scattering dry fertilizer on the soil near the base of the tree and watering to work it in. Follow the dosage range on the fertilizer package to determine the right amount for your container citrus.