Photo: National Gardening Association
Citrus trees make a beautiful and enduring addition to your landscape. You'll enjoy their fruit as well as the sweet, alluring aroma of the blossoms that emerge just before the fruit. For the most part, the areas where home gardeners plant citrus trees in the ground are the same areas where citrus is grown commercially. But if space is limited or the climate isn't suitable, it's still possible to enjoy citrus trees and their bounty year-round by growing them in containers.
If you live in the mild-winter West, Southwest or Southeast, you can grow most kinds of citrus in container outdoors year-round. If your minimum winter temperature regularly dips below 25°F, you can still grow citrus trees if you have a bright spot indoors, or one outside protected from frost.
Any type of citrus tree can grow in a container, at least temporarily, and as with most trees, you'll save money purchasing those already in containers. Certain kinds of lemon and grapefruit, which naturally grow into larger plants, will quickly outgrow their containers. So go with naturally small citrus varieties such as 'Improved Meyer' lemon, 'Bearss' lime, 'Satsuma' mandarin and kumquat. These varieties are more likely to remain both healthy and productive in containers for several years. Indoor citrus growers should follow some additional tips. To harvest fruit, choose a naturally acidic citrus, not a sweet orange or grapefruit. Acidic varieties like 'Improved Meyer' and 'Ponderosa' lemons, calamondins and kumquats are most likely to produce fruit indoors in winter. Other citrus plants will grow and flower but are less likely to produce fruit.
Choose a pot about the size of a 15-gallon nursery container. The ubiquitous half whiskey barrel is a good size, too. Plastic and faux clay pots around 30 inches in diameter work well, but plastic will transmit the sun's heat more readily than wood or clay, and may damage roots. Wooden containers are prone to decay, but you can slow the decay process by coating the interior with asphalt roof patch. Whatever kind of container you choose, make sure it has good drainage. If you're in doubt, drill a few extra holes. To encourage drainage and air circulation around the container, raise it slightly off the ground with planks of wood or bricks.
Use a premixed sterile potting soil designed for container plants, such as Miracle-Gro® Cactus, Palm & Citrus Potting Mix. Don't use garden soil, as once confined in a container, most garden soils are too dense and water will drain too slowly.
Plants in containers need more frequent watering than the same plants in open soil, and citrus are no exception. Especially during hot, dry or windy weather, daily watering may be necessary. The basic rule is to soak the potting soil in the container thoroughly until water drains out the bottom. If the potting soil gets too dry, it may pull away from the sides of the container, which may cause water to drain straight out of the container. To help rewet the dried potting soil, place three or four drops of a mild dish soap on the soil. The soap will help the water soak in so the root ball can expand to fill the container again.
More than most plants, citrus trees are prone to deficiencies in micronutrients like iron, manganese and zinc. Inadequate amounts of any one of them will cause leaves to yellow, while veins remain green. Frequent watering causes these needed nutrients to wash through the potting soil quickly. A controlled-release plant food, such as Miracle-Gro® Shake 'n Feed All Purpose Continuous Release Plant Food, won't wash through the potting soil and releases nutrients slowly over time. The best time to begin feeding citrus trees is in early spring just as new leaves are beginning to emerge.
Gardeners anywhere can grow container citrus by moving the plants into a greenhouse, sunroom or bright indoor location when cold weather arrives. When moving your plants outdoors in spring or back indoors in fall, make the transition gradual. Bring the plants inside at night and place them outside for a few hours a day, increasing their time in the sun and wind. Before moving the plant indoors, shower it completely with warm and slightly soapy water to wash off any bugs. Pests that you don't notice outdoors can become problems once inside.
Compared to the outdoors, homes in winter are darker and warmer, and have much drier air. So anything you can do to provide additional light and extra humidity to your citrus trees will be beneficial. Try grow lights and a tray of pebbles under the pot. Cool, bright rooms, such as a partially heated sunroom, work best.