How to grow citrus trees in pots
All about growing lemon, orange and other citrus trees in pots, including selection, care, transplanting and overwintering
Who wouldn't want to pick fresh lemons or oranges from their own garden? You may think that this privilege is reserved only for growers in tropical and subtropical climates, but there are more and more people from colder regions discovering that they can grow citrus trees in pots and overwinter them indoors.
There is nothing new about growing citrus trees in pots. Rich aristocratic families from the colder parts of Europe were already growing lemon and orange trees in pots in the 17th century, with special heated greenhouses (orangeries) in which citrus trees overwintered together with other tropical and subtropical plants. Today it's a much more accessible practice—you don't need any special equipment or large greenhouses to grow a citrus tree. All you need is a sunny spot by a window and patience.
Growing citrus trees in pots
Citrus trees are native to subtropical and tropical parts of Southeast Asia, where they thrive in year-round high temperatures and high humidity. The best known citrus fruits are the orange, lemon, grapefruit, tangerine, lime and pomelo. All of these can be grown in our own homes if we mimic the conditions that suit citrus plants as closely as possible.
Basic rules for growing citrus trees in pots:
1. Grow citrus trees in places with plenty of direct sunlight
2. Water abundantly, but only after the top 2 inches (5 cm) of soil has dried out
3. Choose a pot with drainage holes that is large enough and especially deep enough for a tree
4. Protect citrus trees in containers from frost by overwintering them indoors, either in a cool, dark place or at room temperature with plenty of light
5. Provide citrus with a well-drained soil and fertilize to resupply nutrients
Growing methods for citrus trees in containers
In colder climates, most citrus trees are grafted on suitable rootstocks or vegetatively propagated from cuttings. Only some species and varieties are usually suitable for growing in containers. Citrus trees that are grafted on dwarfing rootstocks have a stronger root system, ensuring better health of the plant. Citrus trees that are propagated by cutting have the advantage of earlier fruiting, but the disadvantage of more vigorous growth, which means they'll need to be transplanted into larger pots more often. Citrus trees can also be grown from seed, but plants grown this way won't begin fruiting until 5-10 years after planting, and the fruit will not be of the desired quality.
Citrus tree varieties for growing in pots
As citrus trees do not grow to large sizes even in the native conditions, all varieties can be grown in pots. However, dwarf varieties are best suited to container growing. Lemon tree varieties to try are meyer, lisbon, sun gold, yuzu, ponderosa and dwarf eureka. Of the many varieties of tangerine trees, kalamondin, honey, satsuma or mineola tangelo (a hybrid of grapefruit and tangerine) are suitable for indoor growing. Limes (key lime, markut, bears), kumquats and various varieties of oranges are also suitable for indoor cultivation.
Citrus tree growing conditions
Give citrus trees at least 6 (ideally 8 to 10) hours of direct sunlight a day during the growing season. When growing citrus indoors, choose the brightest possible spot near a south-facing window. During the summer, citrus trees in containers do best in a garden or on a patio, so move them outdoors as soon as there is no danger of night frosts and the citrus trees will reward you. However, keep them out of direct sunlight for a couple of weeks, letting them acclimatize in partial shade. During hot summer days, it is ideal to protect citrus trees from the harsh midday sun, which can burn the plant.
In colder climates, the proper light regime is critical for overwintering citrus trees. Ideally, citrus trees should be overwintered indoors at temperatures between 40-50°F (4-10 °C) in a dark room. Do not fertilize citrus trees being overwintered in this way, and water them no more than once a month.
Overwintering at room temperature is problematic for citrus trees because they are not used to higher temperatures unless they also have a sufficient amount of light. However, if you have no alternative but to overwinter a citrus tree at room temperature, at least give the plant plenty of sunlight and regularly mist the leaves.
Watering citrus trees in pots
Citrus plants will tolerate temporary drought better than they will deal with overwatering. Therefore it's important to adjust watering according to growing conditions (light, temperature, humidity, season). Many citrus growers wait to water their plants until the first signs of leaf wilting (curling) to avoid waterlogging the roots. When the root system becomes waterlogged, it is unable to absorb nutrients, which often results in yellowing of the leaves and poor health of the citrus plant. In any case, citrus trees in pots should only be watered when the top 2 inches (5 cm) of soil has dried out.
Usually this means watering 2-3 times a week, but on hot summer days it is sometimes necessary to water citrus trees in pots every day (always in the evening or early in the morning). The need for watering decreases significantly during cloudy days or when the plant is indoors. Any water remaining in the saucer under the pot after ten minutes should be removed. When growing citrus trees indoors, it is beneficial to frequently mist the leaves with water, imulating humid air. Drier summers and wetter winters are typical of Southeast Asia, but an indoor winter environment is often drier than is ideal.
Citrus trees do not tolerate waterlogged soil for long periods of time, so it is important to provide them with a well-drained substrate. There are specialized citrus soil mixes available commercially, but you can also mix a citrus potting soil yourself by combining a succulent substrate (or drainage material like sand, perlite or ceramsite) and garden soil mix in a 1:1 ratio. It is also advisable to place gravel (or polystyrene pebbles) at the bottom of the pot to ensure the quick drainage of excess water.
Fertilizing citrus trees
A combination of slow-release organic fertilizers with special liquid fertilizers designed specifically for citrus (with higher nitrogen and iron content) is best. Liquid fertilizer is best used for citrus trees in spring, and the slow-release fertilizers can be applied for the rest of the growing season. Fertilization should be discontinued during the winter months when citrus trees are dormant.
How to choose the best pot for citrus trees
Pot size for container citrus growing depends on the space you have available. For a young plant up to 2 feet (0.6 m) in height, a pot with a diameter of 1 foot (30 cm) is sufficient, but it must be deeper than it is wide. A sufficiently deep pot will provide good drainage and stability, which is essential even if the plant is already robust. For mature plants, which reach a height of 3-5 feet (1-1.5 m), you'll need a larger container with a minimum diameter of 18-24 inches (45-60 cm).
Plastic pots are less expensive, and most importantly, lighter, which you'll appreciate whenever you have to move your citrus plant from indoors to outdoors and back again. Drainage holes at the bottom of the pot are also essential for growing container citrus trees.
Transplanting citrus trees in containers
Transplant citrus trees into larger pots after they outgrow their original containers. You can tell when it's time for a transplant if the roots are starting to grow out of the top of the container or through the bottom drainage holes. Do not transplant small citrus trees into large pots, as they will not root well through the soil. Always choose a pot that is only about 1 inch (2.5 cm) larger than the original pot, and use fresh soil to replenish the nutrients when transplanting. Remember that the root base close to the trunk should always be slightly above the soil level after transplanting.
Citrus trees benefit from an airy, symmetrical crown, which can be achieved by pruning, especially during the first 5 years of the plant's life. Always remove branches that thicken the crown. The more we cut back, the fewer flowers (and fruit) the citrus tree will bear and the more energy it will expend on growth.
Propagating citrus by cuttings
Citrus trees can be easily propagated from cuttings. Cuttings are obtained by trimming off the terminal (annual) leafy shoots with 3 to 5 leaves or buds from a healthy plant and then trimming back the leaves on the cutting to about half an inch (1cm). Dip the bottom of the cuttings in a growth stimulator before planting. Ensure at least a normal room temperature and high humidity by regularly misting the cuttings after planting. It's likely not all cuttings will survive, so it's best to plant more than you need. Spring is the best time to propagate citrus tree cuttings.
Pests and diseases
Growing citrus trees in colder climates has its advantages. In particular, the common bacterial and viral diseases affecting citruses (bacterial scab, tristeza, melanosis, exocortis and others) are not commonly found in colder climates. However, citrus trees grown in pots can be threatened by common fungal diseases, which can be treated by watering less or by using fungicides.
In colder climates, there aren’t even citrus-specialized pests (citrus leafminer, lemon bud moth, citrus thrips and others). The biggest risk for citrus trees moved outdoors for summer are aphids and white flies, which are treated as for other plants (mechanical removal, biological control or, in the worst case, insecticides). Slugs, snails and birds can also cause great damage to citrus trees. Indoors, citrus trees can be attacked by spider mites or fungus gnats, but these do not pose a great danger to these plants.
The biggest risk for citrus growers, however, is the addictive nature of growing these beautiful and rewarding plants. We know from our own experience that many people start with one lemon tree and after years realize that their garden or balcony has turned into a citrus plantation during the summer. This is just to let unexperienced citrus growers know what they're getting into - you've been warned!
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Author: Daniel Weber