Poncirus trifoliata – Flying Dragon Japanese Bitter Orange is unquestionably an attractive plant, with refreshingly fragrant flowers and handsome autumn foliage, but that is by no means all. For one thing, it comes armed with some seriously offensive weapons in the form of long, sharp thorns, resulting in its regular appearance in the lists of rabbit-proof plants.
This makes it eminently suitable for boundary planting or even as an informal hedge. As well as being an excellent intruder-repellent, it also provides the rootstock for many citrus cultivars, of which it is a close relative.
But perhaps most intriguing is its use in oriental medicine. The extensive list of ailments for which poncirus is prescribed includes typhoid, toothache, hemorrhoids, conjunctivitis, colds and itchy skin.
Poncirus trifoliata is the only species in the genus and can be found growing wild in northern China and Korea, where it thrives on sheltered, sunny hillsides and valleys. It is also called Siberian lemon, since it can tolerate up to -30°C.
Perhaps poncirus’s best feature is its large, cup-shaped white flowers that open in late spring and continue to flower through to early summer, eventually relaxing into saucer-shaped blooms with a deliciously fresh, citrus-like fragrance. It is not uncommon for a second flush of flowers to be produced in autumn, when the fertilized spring flowers will have developed into small, hard, satsuma-like fruits that gradually ripen from green to orange, all the while remaining resolutely inedible.
The foliage is dark green and formed into three-palmate leaves (hence ‘trifoliata’), emerging from stiff, green shoots. In autumn these turn a lovely butter-yellow, combining with the ripened fruits to put on quite a show. P. trifoliata will eventually attain a width and height of about 5m (16ft) if grown as a shrub, but its ability to withstand pruning means that it can be manipulated to fit much smaller spaces.
Growing tips
- Plant in fertile but well-drained soil enriched with garden compost, leaf litter or spent mushroom compost. Use sharp gravel to open up heavier soils before planting.
- When grown as a shrub there is little need for pruning except to remove dead, damaged or diseased shoots, and crossing stems that may rub and become infected.
- If used as a hedge it should be pruned lightly after flowering. This will inevitably mean that some of the fertilized flowers will be removed and therefore potential fruits lost, but these should still form within the hedge.
- A very light trim in autumn is fine, but don’t cut it back too hard or you will chop away the wood on which the following season’s flowers form.
- Seed can be sown in a cold-frame or into pots in a cool, sheltered spot in autumn.
- Take cuttings in summer when the wood is semi-ripe, and use heat under the trays or pots to aid rooting.
- P. trifoliata is blissfully free of pests and diseases.
Planting & Growing
Flying Dragon Japanese Bitter Orange will grow to be about 6 feet tall at maturity, with a spread of 6 feet. It has a low canopy with a typical clearance of 1 foot from the ground, and is suitable for planting under power lines. It grows at a medium rate, and under ideal conditions can be expected to live for 60 years or more.
This shrub does best in full sun to partial shade. It does best in average to evenly moist conditions, but will not tolerate standing water. It is not particular as to soil type or pH. It is somewhat tolerant of urban pollution.
Landscape Attributes
It is a multi-stemmed deciduous shrub with an upright spreading habit of growth. Its average texture blends into the landscape, but can be balanced by one or two finer or coarser trees or shrubs for an effective composition.
This is a relatively low maintenance shrub, and is best pruned in late winter once the threat of extreme cold has passed. Deer don’t particularly care for this plant and will usually leave it alone in favor of tastier treats.
Good companions
Poncirus trifoliata is remarkably tolerant of dry soils, but the flowers can be damaged in very exposed sites; it is therefore best grown against a sunny wall.
It combines well with other spring-flowering border shrubs such as Abutilon x suntense, ribes cultivars, and fire thorn.
Its fragrant flowers make it suitable for a scented border and I have seen it grown with the slightly later-flowering Viburnum x burkwoodii and the early blooming Daphne bholua ‘Jacqueline Postill’ to provide a succession of perfume from winter to mid-summer. Its butter-yellow autumn tints look lovely with the dark purple of Cotinus ‘Grace’ or Corylus maxima ‘Purpurea’.
