Detailed Explanation of Finger Citron Planting Techniques and Management Key Points

(1) Overview

Also known as bergamot.

It is the nearly ripe fruit of the finger citron, a variety of Citrus medica in the genus Citrus of the family Rutaceae. It regulates qi and resolves phlegm, calms the liver and harmonizes the stomach. It mainly treats liver-stomach qi stagnation, cough and asthma, loss of appetite, vomiting, chest and diaphragm distension and fullness, etc. It is mainly produced in Yunnan.

(2) Plant Characteristics

Evergreen shrub or small tree, up to over one zhang (approximately 3.3 m) in height, with hard sharp thorns about 6 cm long at the base of stems and leaves, and new branches triangular in cross-section. Leaves are simple, alternate, oblong-elliptic, with transparent oil dots. Flowers mostly emerge from leaf axils, often several in clusters, with more male flowers and some bisexual flowers; the corolla has five petals, white with a slight purple tinge. The first flowering occurs from the Spring Equinox to Qingming, often with many male flowers, and the fruits set are relatively small; another flowering occurs around the Beginning of Summer, with fruits ripening from September to October, large fruits used for medicinal purposes, with bright yellow skin, wrinkled and glossy, diverging at the top and often opening like fingers, hence the name finger citron; the flesh is white and there are no seeds.

(3) Growth Characteristics

It prefers warm and humid conditions, sufficient sunlight, gentle slopes, soil about 30 cm deep, slightly acidic, sandy loam, well-drained, and relatively fertile sites.

(4) Cultivation Techniques

1. Propagation Methods

(1) Cuttings

This can be done from March to September, preferably after the Summer Solstice at the beginning of the rainy season. Select green and robust branches from the previous year or the current year (avoid using current-year water sprouts), cut them off, remove leaves and thorns, and cut into sections 12-15 cm long with 3-5 buds. Cut the lower end into a 45-degree slant with a sharp knife. Choose sandy loam for the seedbed, plow deeply and harrow finely, with a plant-row spacing of 12-15 cm, insert obliquely into the soil about 2/3 deep, press firm, water, and thereafter keep the sandy soil moist but not waterlogged. Roots form in about 20 days. Weed promptly. If summer is too hot, shade is needed, and apply human manure diluted 10 times. Protect against cold in winter. Field planting can be done in the rainy season of the following year. Water 1-2 days before lifting seedlings, then lift them, taking care not to damage the root system. Field planting spacing is 150-200 cm.

(2) Layering method: from July to August each year, select lower tender branches and press them onto the bed surface with soil; cut them off and transplant from February to March of the following year.

(3) Air layering

Select 2-3-year-old branches, use a knife to cut the bark about 3 cm long (or girdle the bark about 1 cm wide), then wrap with moist soil using a mat or cloth, tie tightly, and water frequently to keep moist. After about 2 months, they can be cut off and transplanted. Alternatively, use a knife to cut halfway into the branch, then bend the branch upward, allowing it to split longitudinally to 10-15 cm, insert a tubular tile piece or a bamboo tube (split in half), tie it, then add moist soil, and after rooting, cut off and transplant.

(4) Grafting

Mostly use cutted citron as rootstock (cutting-propagated finger citron has a fruiting period of about 20 years, while those using citron as rootstock can reach 40-50 years; in addition, wild citron, lemon, and other citrus species can all be used as rootstock). In the rainy season, select citron with a base diameter of about 3 cm, cut off most branches and leaves; separately select finger citron branches from the previous year slightly smaller than the rootstock as scion, peel off the bark on their lower part and approach-graft onto the peeled part of the rootstock, making the two cut surfaces fit closely, tie tightly with rope, and after healing, cut off the upper citron and the lower scion.

(5) Division

Take suckers that arise beside the tree base due to root injury and transplant them.

Finger citron groves must be intercropped with citron, planting one citron for every five to eight finger citron plants, so that the finger citron does not degenerate and the fruits become plump.

2. Field Management

(1) Fertilization

It can be done 4 times a year. After the Beginning of Spring, apply more pre-flowering fertilizer; in April, apply topdressing to reduce fruit drop; in May and June, apply topdressing to promote fruit enlargement; after harvest, apply fertilizer to plump the autumn shoots or restore injuries.

(2) Pruning

Thin out branches and remove summer axillary buds (which do not bear fruit), and thin flowers and fruits (remove dense and small ones), and during the Summer Solstice when fruit drop is settled, cut off old branches, previous branches, and diseased and pest-damaged branches to reduce nutrient consumption.

(3) After harvest, bend branches to inhibit upward growth of finger citron and promote autumn shoot growth, increase fruiting branches, and facilitate pruning and fruit picking. At the same time, combine with intertillage, weeding, and cold protection work.

3. Pest and Disease Control

(1) The main disease is sooty mold. It first infects the leaf surface with small soot-gray spots, then gradually spreads to the entire leaf surface.

Control method: remove diseased leaves promptly, prune appropriately, and increase application of phosphorus and potassium fertilizers.

(2) Longhorn beetle

Larvae bore into branches and feed on the pith, so branch tips appear withered and yellow.

Control method: cut off 3 cm away; if it is still hollow, cut downward until the larva is found. Adults like to move on the trunk at dusk and can be caught and killed.

(3) Aphids

Can be manually caught and killed, or sprayed with tobacco water.

(4) Leaf miners and leaf rollers can be controlled by picking leaves and catching them.

(5) Harvesting and Processing

The medicinal part is the nearly ripe fruit. Harvest in July when the fruit skin changes from dark green to light green (it should not turn yellow and ripe), cut vertically along the fingers into thin slices about 1 cm thick, and sun-dry or dry over a heated kang.