Citrus aurantiifolia Red Lime - Key Lime

The Mexican Lime (Citrus x aurantiifolia 'Red Lime'), or Red Lime, is a moderately vigorous citrus tree, with a well-branched and ornamental habit, and very floriferous in spring. Its small star-shaped white flowers, pleasantly fragrant, are followed by small fruits that are more or less spherical and of a striking red-orange colour ! The dark red and juicy pulp of this citrus fruit is particularly acidic but very aromatic. This species, the least hardy of all citrus trees, has very marked tropical requirements: it perishes below -3°C (26.6 °F) and requires warmth throughout the year to bear fruit well. It will be cultivated in a large container and stored in a slightly heated greenhouse in winter, or in open ground in our warm regions that are not affected by frost.

The Citrus x aurantiifolia is also known as Acid Lime, Country Lemon, Pebble Lemon, Mexican Lime, or Lime Tree of the West Indies depending on the region. It is a spiny bush of the Rutaceae family, with an upright and bushy habit. It is likely native to Southeast Asia, specifically Malaysia and the Philippines, but its exact origin is somewhat unclear. Recent studies tend to prove a hybrid origin between Citrus medica (citron) and C. micrantha (wild lime from the Philippines).

This small tree reaches a height of 3.50 m (11 ft 6 in) and spreads to about 2.50 m. Its branches are short and bear numerous short and very sharp thorns. Not very hardy, it can be planted in open ground only in warm climates like the Mediterranean. Elsewhere, it will be cultivated in a pot and stored at the first signs of cold weather. Primarily grown for its fruit, the Mexican lime blooms abundantly in March-April, and then again, more sporadically, until autumn in warmer climates. It produces small white flowers, slightly tinged with yellow in the centre and with a sweet and delicious neroli fragrance, characteristic of Citrus. They give way to oval to rounded fruits, resembling yellow lemons, with a diameter of 3 to 5 cm (1.2 to 2 in). Their very thin and smooth epidermis, initially dark green in colour, then take on a red-orange hue. The pulp of the fruit, dark red, is both very juicy and very acidic, and contains a few seeds. Fruits can be harvested while still green, when their concentration of essential oils is at its peak. The evergreen and aromatic leaves of this citrus tree are ovate, leathery, small in size, and intensely green.

The fruits of Citrus x aurantifolia are part of the culinary traditions of several Southeast Asian countries, as well as Reunion Island and the Caribbean. Its use is almost as extensive as that of yellow lemons, in savoury or sweet dishes. The juice is used in refreshing drinks and cocktails, adding a touch of acidity and a unique aroma. The zest is sometimes used to flavour pastries. Garnished with a little chilli, the lime is often served with Reunionese dishes and Caribbean ti-punch. In addition to its culinary importance, the Lime Tree is also a medicinal plant whose therapeutic properties, used for centuries in traditional medicine, are now the subject of in-depth scientific research. Lime is less rich in ascorbic acid (Vitamin C), as well as in vitamins A and B, compared to lemons. Easy to store, this citrus fruit was once loaded onto sailing ships, providing a good source of vitamins to fight against scurvy.

Like all Citrus trees, the Lime Tree contains pockets of essential oil in its leaves, flowers, and fruits that are often visible to the naked eye, from which the essential oil with rebalancing and slightly sedative properties is extracted by distillation (flowers and leaves) or by pressing (zest), which helps to realign vital energies. The essential oil is known for its stimulating properties and for facilitating blood circulation. Its fragrance is described as fresh, lemony, tangy, with slightly sweet and bitter notes.

Not very hardy, the Citrus aurantifolia begins to suffer from cold temperatures as low as 0°C (32 °F). It is a self-fertile bush, which means that a single individual is sufficient for complete pollination and fruiting.