Lime tree: tips on lime tree cultivation & care

Lime tree: tips on lime tree cultivation & care

To many people, limes are best known as an ingredient in sweet and sour cocktails. We will show you everything you need to know about the cultivation and care of lime trees.

The small, green citrus hybrid, which is commonly simply referred to as lime, is actually called Key lime (Citrus x aurantiifolia). It is also known by several other names, such as Mexican lime or bartender’s lime. If you are planning to plant a Key lime tree on your balcony or terrace, you will have to pay attention to a few things. In this article, you can learn everything you need to know about planting limes as well as the proper lime tree care.

Origin and characteristics of the Key lime

The Key lime is a plant species that belongs to the Citrus genus in the Rutaceae family – just like the lemon (Citrus x limon) and the orange (Citrus x sinensis). The Key lime tree probably originated from the area of the Malay Archipelago but has been cultivated for centuries in many tropical areas around the world. Its name “Key lime” is derived from the lime’s growing areas on the Florida Keys.

The Key lime grows as a strongly branched shrub with a short stem and a full, lush crown. The plant’s thin shoots are covered in thorns. In its tropical home, the lime tree can grow to a size of up to four metres, but it will remain much smaller when grown in a pot in temperate climates. The lime tree leaves are six to eight centimetres long, have a light green colour and are long and oval-shaped. They are fairly similar to the leaves of the bitter orange (Citrus x aurantium).

The lime tree fruit is a lot less shiny than other citrus fruit varieties. Its flowers have a wonderful and intense scent and start blooming in early summer. The lime tree flowers are cream-coloured and can take on a slight violet hue in intense sunshine. Limes have a sour and fruity taste and are therefore particularly popular in cocktails. The lime’s essential oil is also used commercially, especially in the beauty and cosmetics industry.

Lime tree varieties

In addition to the Key lime, there are several other types of lime trees. These include, for example:

  • Key lime or Mexican lime (Citrus x aurantiifolia): overwintering this classic lime can be a little tricky
  • Persian lime or Tahiti lime (Citrus x latifolia): bears oval rather than round fruits, requires less heat and light than the Key lime
  • Rangpur lime (Citrus x limonia): this type of lime is also called mandarin lime, because it has orange flesh under its green skin
  • Palestinian sweet lime (Citrus limettoides): robust and low-maintenance, similar to the Persian lime
  • Kaffir lime (Citrus hystrix): its leaves are commonly used in Thai cuisine
  • Pursha lime or Roman lime (Citrus limetta x Citrus sinensis): also called sweet lime because its acidity is milder than that of other lime varieties
  • Australian finger lime or caviar lime (Microcitrus australasica): this species carries finger-shaped fruits with flesh that resembles caviar

Buying Key limes: what to look for

We recommend purchasing your lime tree from a tree nursery of your choice. Key limes are usually grafted, so that – depending on the stock and type of grafting – even smaller trees can bear fruits. The quality of the grafting determines the quality of the lime tree. The stock and scion should be intergrown tightly. The bark at the grafting point should not have any open areas through which diseases could get into the tree. For this reason, you should only purchase your lime tree from experts who can assess the plant’s quality properly. You should also make sure that your Key lime is in good health. Are the leaves and stem intact? Can you detect any traces of pests or diseases? Does the plant look vital? These are the questions you should keep in mind when buying your lime tree.

How to grow a lime tree

The Key lime’s alternative name Mexican lime provides some information about the plant’s habitat requirements. Mexico’s climate is subtropical and tropical, therefore the lime tree can be planted outdoors there. However, in temperate climates, Key limes need to be grown in pots. In summer, though, the plant can enjoy the sun outdoors in the garden or balcony. In the winter, the lime tree should be moved to a more sheltered and heated place.

Your lime tree’s location should be as sunny as possible. Limes require even more heat and light than lemons or oranges. The energy which the plants absorb is then put into the aroma of their fruits. If your lime tree spends too much time in the shade, the taste of the fruit will suffer.

Tip: If the plant doesn’t get enough light in the conservatory, it may shed its leaves completely. But don’t worry, this does not mean that your plant is sick. The lime will sprout again in spring and the crown of the tree will become green again.

The substrate for the lime tree should be permeable with a high mineral content. To achieve this, you can mix the soil with 30 % of mineral materials such as gravel, expanded clay or rhassoul and 10 % coconut fibres.

An overview of the Key lime’s location requirements:

  • Sunny, warm location
  • In summer in the garden, on the terrace or the balcony
  • In winter in the conservatory
  • Permeable soil with high mineral content

Tip: If the roots of the lime tree get too warm, they will stop absorbing water and nutrients. Therefore, the pot should not be exposed to too much direct sunlight. You should also make sure to keep the underfloor heating of the plant’s winter quarters off.

Propagating lime trees

Limes can be propagated via seeds and cuttings. When propagating lime trees by cuttings, cut them from the top of the plant and take off all the leaves. Ideally, you should use a semi-wooden cutting of about 15 to 20 centimetres with between 5 and 11 buds. You should then dip the cuttings in some powdered rooting hormones and place them in loose cutting soil. Two to five buds should be covered by soil, while other three to six should remain above the soil. Finally, moisten the soil and the cuttings slightly. The cuttings will then take root under some foil at temperatures of about 20 to 25 °C.

Lime tree care

If you want your lime tree to have a long life and a rich harvest, you will have to employ some tending strategies. In the following, we will give you some tips on repotting, watering, fertilising and pruning lime trees.

lime tree care
In the following, we will explain how best to take care of your lime tree so that you can achieve a full lime harvest [ Thongjam]

Repotting lime trees

Like any other potted plant, your lime tree has to be repotted regularly. When the roots have penetrated the entire pot, it is time to repot your lime tree. The best time for this is in March, right before the plant starts to sprout again. You should choose a pot made of clay or plastic that is only a little bigger than the old pot. In addition, your pot needs a drainage layer so that the water can drain off well and no waterlogging occurs. Gravel or fragments of clay, for example, are well-suited as drainage material.

To repot, take the root ball out of the pot and examine if it is healthy. Cut away dead root material.

How to repot lime trees:

  • Repot young plants every two years
  • Choose a pot that is only a little larger than the old one
  • Enrich potting soil with mineral material and coconut fibres
  • Add a drainage layer
  • Insert root ball and straighten it
  • Fill the pot with soil
  • Water the plant well

Watering lime trees

The amount of water lime trees need depends on its growth, which can vary greatly depending on the weather conditions. For that reason, you should only water you lime tree if necessary. Compared to lemon trees, the lime tree requires a lot less water. You should therefore water it carefully and not too much. As a rule of thumb: lime trees need water when half of the soil has dried out. You can use both rainwater or tap water to completely soak the root ball of your plant. After that, you can wait a few days until watering again.

Pruning lime trees

Limes grow very slowly; a regular pruning is therefore not necessary. In general, though, lime trees are tolerant of pruning and cutting them back does not harm them. When pruning your lime tree, you should be careful to always cut right above an outward-facing bud or node. Dead branches or ones that are affected by diseases or pests can be removed at any time. You should always use sharp gardening shears for pruning lime trees.

Fertilising lime trees

Lime trees have a high standard when it comes to fertiliser. Special citrus fertilisers composed of 10 % nitrogen, 2 % phosphate and 7 % potassium are best suited for your lime tree. From March to October, during the plant’s main growth period, we recommend fertilising once every week. Since citrus fertilisers usually come in a liquid form, they can be added while watering the plant. Organic fertilisers are also a good alternative for Key lime plants.

In winter, limes should be fertilised as long as they are growing. This could be the case well into November, sometimes even December, if your plant is spending the winter in a well-heated place with plenty of light. If the plant’s winter quarters are rather dark and shady, you can stop fertilising towards the end of September. This will slow down the formation of new shoots and leaves.

Overwintering lime trees

The Key lime is not winter-hardy and therefore has to be kept in a warm and protected place for the winter. Also, the plant doesn’t hibernate and needs as much light as it can possibly get, even in winter. To successfully overwinter the lime tree, temperatures between 8 and 15 °C are ideal. The warmer the location of your lime tree in winter, the brighter it should be. Conversely, this means that it should not be too warm if the lime plant is in a dark location. If the ratio of light to heat is not ideal, the plant might lose its leaves. If the tree has lost all of its leaves, you should only water it very sparingly. However, the plant should never dry out completely, even in winter. Soaking the substrate in water is a better option than watering your lime tree frequently with small amounts of water. Lime trees also like very humid air in winter. If you want to do your plant some good, spray it regularly with some water.

How to overwinter your lime tree:

  • Temperatures between 8 – 15 °C are ideal
  • As sunny as possible
  • Watering regularly
  • Increase air humidity by spraying the plant
  • The warmer it is, the more light the lime needs

Tip: Unfortunately, winters in temperate climates are often cloudy and dark. It is therefore recommended to use plant growing lamps for Key lime trees at temperatures above 10 °C.

Harvesting and storing limes

In tropical regions, at constant temperatures, the skin of the lime tree’s fruit remains green until it is fully ripe. But due to the low temperatures at night in temperate climate zones, the skin will turn light green to yellow.

The limes’ harvest season is late autumn, sometimes even in winter. You can harvest your limes as soon as the fruits become softer and the skin turns a little lighter. If you want to harvest green limes, you should cut them off earlier. Like all citrus fruits, it is best to cut off the limes with some scissors, about one centimetre above the base of the stem. After harvesting the fruits, they should be cleaned thoroughly. They can then be stored in the refrigerator, where the risk of rotting and mould is the lowest.

Using limes in the kitchen

There is a huge variety of ways in which you can use limes in the kitchen. Limes are great in desserts and pastries, but also as a dressing or a juicy and fruity addition to hearty dishes.

key lime dessert
One of the best ways to use Key limes in the kitchen is to make lime cheesecake [ Tatiana]

Of course, lime is also an important ingredient in numerous cocktails. Cocktail classics with lime include caipirinhas, mojitos or margaritas. For a tasty caipirinha, you will need two untreated limes. Sprinkle them with some brown sugar and crushed with a pestle, so that the aroma unfolds. Then, add 4 cl of cachaça, fill up the glass with ice and your cocktail is ready. It doesn’t always have to be alcohol, though: limes are also great to give some flavour to your water. They are also often used as a dressing in Mexican cuisine. Just pour a few drops over your tacos or into the guacamole and enjoy the refreshing taste.

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