Bitter Orange, Hardy orange, Trifoliat Orange, Japanese Hardy Orange
Poncirus trifoliata

Family: Rutaceae

What it is like

An attractive deciduous shrub growing up to six feet tall, this is the only fruit-bearing shrub of the orange family that is genuinely hardy in Britain. The species is unusual among citrus for having deciduous, compound leaves and pubescent (downy) fruit. The fruit, unfortunately, is inedible raw, though it can be used in conserves etc. This shrub is very sparsely leaved, much of the photosynthesis taking place in the young stems, but it has very large thorns which make it both attractive and a very useful barrier when grown as a hedge. It fruits best in a sunny position. A hybrid between this plant and the orange, called a 'Citrange', is hardy in south-west England where it bears somewhat sweeter fruits. A smaller cultivar "Flying Dragon" has twisted, contorted stems making an excellent barrier hedge. Poncirus trifoliata has some medicinal uses and is widely used in Oriental medicine as a treatment for allergic inflammation. Fragrant flowers and handsome autumn foliage. US Hardiness Zones: 6-9. Main Bloom Time: Early spring, Late spring, Mid spring. Form: Rounded.

Poncirus trifoliata is a deciduous Shrub growing to 3 m (9ft) by 3 m (9ft) at a slow rate. See above for USDA hardiness. It is hardy to UK zone 5 and is not frost tender. It is in flower from April to May, and the seeds ripen from September to November. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. The plant is self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very acid and very alkaline soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

Height (m): 3

Where it is found

Hedgerows. Woods in mountains and hills in Korea.

E. Asia - C. and S. China, Korea.

Conservation Status:

Countries/locations it is found in

North America,

How it is used

Food

Rating: 3

Fruit - cooked. A bitter and acrid flavour, but it can be used to make a marmalade. The fruit is also used to make a refreshing drink. The freshly picked fruit yields little juice but if stored for 2 weeks it will yield about 20% juice, which is rich in vitamin C. Yields of up to 14 kilos of fruit per plant have been achieved in America. The fruit is 2 - 3cm wide, though most of this is the skin. The fruit peel can be used as a flavouring. Young leaves - cooked.

Condiment: the various plants that are used as flavourings, either as herbs, spices or condiments.

Medicine

Rating: 2

The thorns are used in the treatment of toothache. The stem bark is used in the treatment of colds. The fruits contain a number of medically active constituents including flavonoids, coumarins, monoterpenes and alkaloids. The fruit, with the endocarp and seeds removed, is carminative, deobstruent and expectorant. It is used in the treatment of dyspepsia, constipation and abdominal distension, stuffy sensation in the chest, prolapse of the uterus, rectum and stomach. It is milder in effect than the immature fruit and is better used for removing stagnancy of food and vital energy in the spleen and stomach. The unripe fruit is antidiarrheic, antiemetic, antispasmodic, deobstruent, digestive, diuretic, laxative, stimulant, stomachic and vasoconstrictor. It is used in the treatment of dyspepsia, constipation and abdominal distension, stuffy sensation in the chest, prolapse of the uterus, rectum and stomach, shock.

Antiemetic: Prevents vomiting.

Antispasmodic: Relaxes muscular spasms and cramps, calming nervous irritation.

Carminative: Reduces flatulence and expels gas from the intestines.

Deobstruent: Clears obstructions from the natural ducts of the body.

Digestive: Aids digestion.

Diuretic: Acts on the kidneys, promoting the flow of urine.

Expectorant: Clears phlegm from the chest by inducing coughing.

Laxative: Stimulates bowel movements in a fairly gentle manner.

Odontalgic: Treats toothache (temporary measure only) and other problems of the teeth and gums.

Stimulant: Excites or quickens activity of the physiological processes. Faster acting than a tonic but differing from a narcotic in that it does not give a false sense of well-being.

Stomachic: Aids and improves the action of the stomach.

Vasoconstrictor: Narrows the blood vessels, thereby increasing blood pressure.

Vitamin C: Plants good for their vitamin C content

Other

Rating: 3

Used as a rootstock for Citrus species (oranges, lemons etc). It confers an extra 3°c resistance to the cold. The plant is very thorny and makes an excellent impenetrable barrier or hedge, though this barrier is not very dense. The plants are very tolerant of pruning, they are best clipped in early summer shortly after flowering.

Hedge: Plants that can be grown as hedges.

Rootstock: Plants used as the rootstock for grafting scions onto.

Espalier: A tree or other plant that is trained to grow flat against a support (such as a trellis or wall).

Food Forest: Plants for Edible Forest Gardens and Food Forests.

Hedge: Hedge

Scented Plants: Plants noted for their scent

How it is grown

Landscape Uses:Border, Espalier, Foundation, Hedge, Screen, Standard, Winter interest. An easily grown plant, it succeeds in an ordinary garden soil, preferably well-drained, but prefers a fertile light sandy soil in a sunny position. A plant is growing and fruiting well in light woodland shade at Cambridge Botanical Gardens. Plants dislike soil cultivation close to their roots and so should either be well mulched to prevent weed growth, or hand weeded. Succeeds in poor acid soils. Plants also succeed in chalk-laden soils. Hardy to about -15°c. Plants have survived -30°c of frost without injury according to one report. The bitter orange hybridizes with Citrus species and could possibly be used in breeding programmes to produce hardier forms of oranges, lemons etc. It could also be of value in conferring disease resistance, tolerance of poorer soils and dwarfing characteristics. The flowers are produced on the previous years wood. The whole plant, but especially the flowers, is strongly aromatic. A very ornamental plant, the fruits are freely formed in south-western Britain. A hedge at Wisley in a semi-shaded position fruits heavily in most years. Another report says that warm autumns are required if the plant is to fruit freely. Fertile seed is produced after warm summers. Plants are relatively short-lived, deteriorating after about 25 years. Special Features: Not North American native, Naturalizing, Fragrant flowers, Attractive flowers or blooms.

Propagating it: Seed - best sown as soon as it is ripe in a cold frame. Cold stratify stored seed for 4 weeks and sow early spring in a greenhouse. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse for at least their first winter. Plant them out into their permanent positions in early summer. Cuttings of half-ripe wood, June/July in a frame.

Best place to grow: Woodland Garden Sunny Edge; Dappled Shade; Hedge;

Habit: Shrub

Hardiness: 6-9

Growth: Slow

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Moist

Things to keep in mind

Its other names

Local names

Synonyms

Aegle sepiaria. Citrus trifoliata. Limonia trifoliata.