Citron Tree (Citrus medica)

The Citron tree (Citrus medica), which grows in USDA hardiness zones 10 to 11, is a slow-growing shrub or small tree that can reach up to 8 to 15 feet. It can be quite difficult to grow citron plants in colder climates.

I. Appearance and Characteristics

The citron (Citrus medica), historically cedrate, is a large fragrant citrus fruit with a thick rind. It is said to resemble a ‘huge, rough lemon’. It is one of the original citrus fruits from which all other citrus types developed through natural hybrid speciation or artificial hybridization. Though citron cultivars take on a wide variety of physical forms, they are all closely related genetically. It is used in Asian and Mediterranean cuisine, traditional medicines, perfume, and religious rituals and offerings. Hybrids of citrons with other citrus are commercially more prominent, notably lemons and many limes.

Citrus medica is a slow-growing shrub or small tree that reaches a height of about 8 to 15 ft (2 to 5 m). It has irregular straggling branches and stiff twigs and long spines at the leaf axils. The evergreen leaves are green and lemon-scented with slightly serrate edges, ovate-lanceolate or ovate elliptic 2.5 to 7.0 inches long. Petioles are usually wingless or with minor wings. The clustered flowers of the acidic varieties are purplish tinted from outside, but the sweet ones are white-yellowish.

The citron fruit is usually ovate or oblong, narrowing towards the stylar end. However, the citron’s fruit shape is highly variable, due to the large quantity of albedo, which forms independently according to the fruits’ position on the tree, twig orientation, and many other factors. The rind is leathery, furrowed, and adherent. The inner portion is thick, white and hard; the outer is uniformly thin and very fragrant. The pulp is usually acidic, but also can be sweet, and some varieties are entirely pulpless.

Most citron varieties contain a large number of monoembryonic seeds. The seeds are white with dark inner coats and red-purplish chalazal spots for the acidic varieties, and colorless for the sweet ones. Some citron varieties have persistent styles which do not fall off after fecundation. Those are usually preferred for ritual etrog use in Judaism.

Some citrons have medium-sized oil bubbles at the outer surface, medially distant to each other. Some varieties are ribbed and faintly warted on the outer surface. A fingered citron variety is commonly called Buddha’s hand.

The color varies from green, when unripe, to a yellow-orange when overripe. The citron does not fall off the tree and can reach 8–10 pounds (4–5 kg) if not picked before fully mature. However, they should be picked before the winter, as the branches might bend or break to the ground, and may cause numerous fungal diseases for the tree.

Despite the wide variety of forms taken on by the fruit, citrons are all closely related genetically, representing a single species. Genetic analysis divides the known cultivars into three clusters: a Mediterranean cluster thought to have originated in India, and two clusters predominantly found in China, one representing the fingered citrons, and another consisting of non-fingered varieties.

II. How to Grow and Care

Watering

The Buddha’s hand citron tree normally doesn’t require any specific watering pattern, except in hotter countries and those countries that suffer from strong droughts in summer.

Never water too much, because the Buddha’s hand citron tree doesn’t cope well with flooded soil.

You know if your Buddha’s hand trees need water when their leaves start drooping or bending over.
It is best to water with collected rain water, because they are vulnerable to calcium ions in water, and tap water often has many.

The Buddha’s hand citron tree planted in a pot doesn’t have the same water needs as a normal ground-grown tree, because the soil in the pot dries up much faster.

• Water as soon as the soil is dry without flooding the pot.
• Best to water with rain water.
• In winter, water as little as possible (once a fortnight should cover its needs).

Planting Instructions

Planting directly in the ground

Before you start, you should know that Buddha’s hand does not resist freezing, and will start suffering when temperatures drop below 40°F (5°C).

Only try to plant the Buddha’s hand citron tree directly in the ground in areas where the winter climate is very mild, or in winter gardens.

• Avoid planting Buddha’s hand citron tree in full summer, when temperatures are high.
• Choose a sun-bathed area sheltered from heavy wind.
• Place a drainage layer at the bottom of the hole with gravel or clay marbles.
• Mix garden soil with citrus-specific planting soil mix, if you haven’t any, with regular planting soil mix.
• Fill the hole in with this mix and press it down.
• Water and press down again.
• Water regularly during the first 2 years after planting without ever flooding the roots.

Planting in pots

This is probably the best way to grow Buddha’s hand citron trees in our temperate latitudes, because our climate is too cool.

• Just as for the potted lemon tree, Buddha’s hand citron will do very well in a pot.
• You will need to bring it indoors from October to May in a lean-in or a greenhouse that isn’t heated.
• Perform a repotting after having purchased your plant, and then, repeat this every 2 or 3 years.

Pruning

Since the size of the Buddha’s hand tree when adult is quite small, about 6 to 10 feet (2 to 3 meters), normally you can avoid any measure of pruning.

However, you can prune a few times to increase growth, help the branches to grow more dense, and get more fruits.

Pruning is best performed in spring, ideally during the months of March, April or May, after the citron harvest.

Pruning should be restricted to the bare minimum: Using a properly disinfected hand pruner, cut each new shoot back to more or less half its length, taking great care to cut just above a leaf.

• Remove suckers that are growing at the wrong place, such as along the trunk of where branches meet.
• Cut away scraggly branches or inward-growing branches.
• Remove dead wood regularly and clear the inside branches to let light penetrate to the center again.

Pests and Diseases

Similar to lemon trees, the Buddha’s hand citron tree is vulnerable to the same diseases.

Fruit rot, aphids or mealybugs are some of the many diseases and parasites that Buddha’s hand trees can suffer from.

• European brown rot – citrons rot while still on the citron tree
• Scale insects – whitish masses colonize leaves
• Aphids – leaves curl up and fall off
• Thrips – especially attacking fruits, creating blotches of silver-white on their peel

III. Uses and Benefits

• Religious

In Judaism

The citron (the word for which in Hebrew is etrog) is used by Jews for a religious ritual during the Jewish harvest holiday of Sukkot, the Feast of Tabernacles; therefore, it is considered to be a Jewish symbol, one found on various Hebrew antiques and archaeological findings.

In Buddhism

A variety of citron native to China has sections that separate into finger-like parts and is used as an offering in Buddhist temples.

In Hinduism

In Nepal, the citron (Nepali: बिमिरो, romanized: bimiro) is worshipped during the Bhai Tika ceremony during Tihar. The worship is thought to stem from the belief that it is a favorite of Yama, Hindu god of death, and his sister Yami.

• Medicinal uses

From ancient through medieval times, the citron was used mainly for supposed medical purposes to combat seasickness, scurvy and other disorders. The essential oil of the flavedo (the outermost, pigmented layer of rind) was also regarded as an antibiotic.

The juice of the citron has a high content of vitamin C and dietary fiber (pectin) which can be extracted from the thick albedo of the citron.

• Culinary uses

While the lemon and orange are primarily peeled to consume their pulpy and juicy segments, the citron’s pulp is dry, containing a small quantity of juice, if any. The main content of a citron fruit is its thick white rind, which adheres to the segments and cannot easily be separated from them. The citron gets halved and depulped, then its rind (the thicker the better) is cut into pieces. Those are cooked in sugar syrup and used as a spoon sweet known in Greek as “kítro glykó” (κίτρο γλυκό), or diced and candied with sugar and used as a confection in cakes. In Italy, a soft drink called “Cedrata” is made from the fruit.

In Samoa a refreshing drink called “vai tipolo” is made from squeezed juice. It is also added to a raw fish dish called “oka” and to a variation of palusami or luáu.

Citron is a regularly used item in Asian cuisine.

Today the citron is also used for the fragrance or zest of its flavedo, but the most important part is still the inner rind (known as pith or albedo), which is a fairly important article in international trade and is widely employed in the food industry as succade, as it is known when it is candied in sugar.

The dozens of varieties of citron are collectively known as Lebu in Bangladesh, West Bengal, where it is the primary citrus fruit.

In Iran the citron’s thick white rind is used to make jam; in Pakistan the fruit is used to make jam but is also pickled; in South Indian cuisine, some varieties of citron (collectively referred to as “Narthangai” in Tamil and “Heralikayi” in Kannada) are widely used in pickles and preserves. In Karnataka, heralikayi (citron) is used to make lemon rice. In Kutch, Gujarat, it is used to make pickle, wherein entire slices of fruits are salted, dried and mixed with jaggery and spices to make sweet spicy pickle. In the United States, citron is an important ingredient in holiday fruitcakes.

• Perfumery

For many centuries, citron’s fragrant essential oil (oil of cedrate) has been used in perfumery, the same oil that was used medicinally for its antibiotic properties. Its major constituent is limonene.

IV. Harvesting and Storage

Expect your tree to begin blossoming when it is about three years old. Pollinate the blooms yourself if the plant is indoors at the time. Support the branches with forked sticks if they begin bending under the weight of the fruits. While the tree is still young, pinch the vertical tip off your tree to force the branch out. Pinch back the side shoots as well while the plant is still small to get short, strong horizontal branches that will be capable of bearing the largest citron fruits.

Harvest the fruits when they are about 5 inches long and still slightly green if you wish to candy the peels. Wait for them to turn yellow and more fragrant if you want to make something like a pomander. The Buddha’s Hand type of citron has fruits with fingers, and the Turunji type can produce fruits as large as 7 pounds. Like most citrus trees, citron has thorns, so handle the tree with care.