Lemon Tree

The lemon tree (Citrus limon) originally comes from Asia (China and India), where it has been cultivated for over a thousand years. It is presumed that it came about from a cross between the bitter orange (Citrus aurantium) and citron (Citrus medica). The lemon tree is part of the Citrus genus within the rue or citrus family (Rutaceae). It is cultivated for its fruit as well as its attractiveness as a decorative plant, and is popular all around the globe. In temperate climates, this tropical plant must be overwintered somewhere without frost. Lemons also play an important role in natural medicine, as the essential oils are used to treat insect bites.

Lemon trees grow round, tending to spread and expand horizontally. The crown can be shaped through regular trimming. This tree’s maximum height of 13 to 16 feet tall depends on its base stock. Some varieties have thorns on young shoots. Citrus plants can also be trained on a trellis in suitable locations.

The lemon tree’s mostly (but not always) shiny, evergreen leaves are very decorative. They are elongated, pointed ovals. They are slightly serrated at the edges and sit on stalks. Sunlight releases the essential oils in the foliage, so the whole tree smells of lemon.

The Citrus limon’s flowers are characterized by pink buds that open from May to display white flowers all through summer. The lemon tree’s flowers also give off an intense, fruity scent. Flowers and fruits are often seen at the same time. Pollination occurs through wind and insects but also self-fertilization.

The lemon tree bears many fruits even in the cool Central European climate. These are a special kind of berry. The elongated oval fruits of most varieties turn from green to yellow as they ripen. The flesh of the fruit inside is also yellow. Due to their high citric acid content, lemons taste sour. They contain Vitamin C, pectin and essential oils. They are among the fruits with the lowest sugar content. They can be eaten raw but can also be prepared in a variety of ways. The lemon fruit harvest alternates, meaning that there will be a bumper crop of fruit one year followed by a meagre harvest the following year. This is normal for lemon trees, not a result of poor care.

The lemon tree needs a light, sunny location sheltered from wind and rain. It is suitable for container gardening on south-facing balconies and terraces as well as cold and heated conservatories. Tip: a lemon tree complete with its container can be buried in a sunny bed over summer. In fall, it can be dug up and moved to its winter home. Due to its pleasant scent, the lemon tree should be positioned near a seating area. Citrus limon is not winter hardy so must spend winter indoors.

The lemon tree is planted in high-quality, peat-free potting soil or special citrus soil. This has an especially high humus content and permeability that will benefit the lemon tree.

A lemon tree is watered infrequently but thoroughly, and potentially daily in hot summers. The top 1.18 to 1.57 inches of soil should be fully dry before watering. Gardeners used to be advised to water lemon trees with low-lime water, but we now know that this citrus has a high calcium requirement. Hard, limey tap water is therefore the right choice. After watering, make sure that the plants are not standing in water. Waterlogging leads to leaf loss and shoot death.

When fertilizing citrus plants, it’s easy to make mistakes. Citrus limon needs a lot of nitrogen but little phosphate. It’s therefore best to use a leafy plant food or a special citrus food for your lemon tree. Fertilize every two weeks in spring as the plant grows, then every week from June to September.

For healthy growth, young lemon trees, like other citrus plants, should be repotted regularly. This is best done either in spring or early summer. Reasons for repotting are: a pot that has become too small (for young plants every two years, for older plants about every four years) or a new purchase, because very few container plants from the specialized trade are in the soil suitable for lemons. Old lemon trees, on the other hand, do not repot, but only fill the pot with fresh substrate. For repotting, choose a little larger plant pot, cover the drainage holes with shards of clay and fill a drainage layer of expanded clay. Then add citrus soil loosened with a little sand. Carefully loosen the root ball of the lemon tree with your fingers and shake out old soil. When planting, make sure the root ball ends up no more than two inches below the rim of the pot to keep the grafting area free of soil. After repotting, water the lemon tree carefully. Excess water must be able to drain.

The lemon tree spreads as it grows, like all citrus species, meaning that it doesn’t form an attractive crown on its own. To shape it, you’ll need to regularly prune your lemon tree. Thankfully, these plants are very tolerant of pruning. Citrus limon tolerates pruning all year round, but large-scale pruning should be reserved for the end of February. To form an even crown, you will have to turn a thick central branch into the main branch. Secure this to a stake to act as somewhat of a central leader. All other central branches should be completely removed, apart from three of four around the central leader. The outer side shoots should be shortened and potentially guided into position with wire or twine to encourage an attractive crown.

If the crown becomes misshapen, occasionally removing any long or disruptive branches, which may even be growing intertwined, should be sufficient to correct the course. Always cut the whole branch to ensure that enough light makes it inside the crown. Branches that have produced fruit should be cut back by around half each year. This will create fresh fruiting branches. Always cut slightly above the buds or leaves, at an angle with the direction of growth. If a lemon tree has become over-mature and only has a few leaves remaining, it can be cut back to around 5.90 inches. When the plant begins to show strong growth, you can apply the crown development technique outlined above. Branches growing underneath the grafting site are known as suckers. These are removed right at the base.

Before the first frost, citrus plants should move to their winter habitat, where they should stay until April/May. The lemon tree prefers to winter in a room between 37.4 and 55.4 degrees Fahrenheit. This should be on the darker side rather than bathed in sunlight. Lemon variety “Kucle” tolerates temperatures up to 64.4 degrees Fahrenheit. Lemon trees are watered less frequently in winter; watering can be flexibly based on need. The root ball should not be allowed to fully dry out. As a rule of thumb: the colder the winter habitat is, the darker it should be. Citrus plants will quickly descend into chaos when faced with a combination of cold and light. If the lemon tree’s foliage is warmed by bright sunlight in its winter habitat but the root ball remains cold (on a cold stone floor, for example), the leaves will burst back into life but the roots will not. The result is a lack of water, followed by extreme leaf loss. It is therefore advisable to overwinter lemon trees in a cool place and shelter them from too much light, or to simply overwinter the tree in a warm place (over 68 degrees Fahrenheit). In this case, the Citrus limon will continue to grow and must be further watered and lightly fertilized throughout the winter months.

The most common lemon variety is the thornless Citrus limon “Eureka”, which has round, dark green leaves. The small-fruiting variety “Meyer” is suitable for growing as a container plant. Its growth is compact and its fruit less sour. The colorful lemon variety “Foliis Variegatis” boasts particularly attractive leaves. “Lunario” is fast-growing and has few thorns. Its fruit is elongated and pale yellow.

In nurseries, lemon trees are propagated through grafting. Hobbyists are best off using cuttings. In spring or fall, take head cuttings from plants that are about half a year old and slightly woody at the bottom. There should be three to five intact buds on the cutting. Remove the lower leaves, put the cutting in rooting powder and place the shoot into a bowl or a pot with potting soil. Tip: mix your potting soil with a little sand and a handful of algae lime to improve your results. Your cuttings can then be watered and covered with a see-through cover. Lemon cuttings like high soil temperatures of around 82.4 degrees Fahrenheit as offered by a position near heaters or a heated propagation station. The first roots should form after four to six weeks. Once the cuttings have begun to put out new shoots, the cover can be removed and cuttings potted into their own pots.

The beginning of May comes with the first aphid infestations. This often results in dark rust fungi. Especially in warm, dry winter habitats, spider mites and scale insects can take hold on your lemon tree. Spider mites can be identified from their silvery webs, while scale insects can be spotted through brown bumps on leaves and stems. Wooly webs in the leaf axils and underside of leaves indicate mealy bugs. If the leaves are turning yellow, the lemon tree is probably suffering from a deficiency (chlorosis) – usually due to a lack of calcium or iron. Care issues such as excess fertilization or spent soil can also be the cause. If the lemon tree was planted too deep, root crown rot may occur. If Citrus limon is watered irregularly, the fruit can burst.