Photo: Jebulon — Public domain · source
Survives zone 6 through 9
Harvest calendar
Best planted in early spring after your last frost, or in fall before the ground freezes, depending on your climate.
Citrus trifoliata (trifoliate orange, hardy orange) is a deciduous, extremely thorny, cold-hardy citrus relative grown chiefly as rootstock and as an ornamental or security hedge — its fruit is bitter and essentially inedible fresh, and the plant has naturalized in parts of the southeastern United States.
- Hardiness
- Zone 6–9
- Habit
- Shrub
- Edible part
- Fruit
- Ripens
- Winter (citrus)
- Mature size
- Deciduous thorny shrub or small tree 2–6 m; grown as a hedge and as the standard cold-hardy rootstock
- Light
- Full sun
- Soil pH
- 6.0–6.5 (slightly acid)
- Environment
- Temperate
- Native range
- Native to northern China and Korea; long cultivated elsewhere and now naturalized in parts of the southeastern United States, from around Pennsylvania south and west to northern Florida and eastern Texas.
- Status
- Rootstock
- Years to fruit
- 2–3 yrs
- Growth speed
- Rapid growth rate, typically reaching 8–20 ft tall and 6–15 ft wide at maturity.
- Spacing
- 240 cm (94 in) apart — about 5.8 m² (62 sq ft) per plant
- Leaf shape
- Compound, trifoliate (three-leaflet) leaves — a genuinely unusual trait among Citrus, which are mostly simple-leaved — with obovate-to-elliptic leaflets and winged petioles. Also unusual for being deciduous: foliage emerges yellow-green, matures to dark green, then turns yellow before dropping in fall, unlike most evergreen Citrus.
- Root system
- Notably shallow and small for a citrus rootstock — highly fibrous feeder roots but few, small lateral roots — giving it relatively poor drought tolerance despite being the most widely used cold-hardy citrus rootstock in the world.
- Fruit description
- A small (2.5–7.6 cm), globose, lightly downy, dull lemon-yellow fruit with a thick, oil-gland-studded peel and numerous seeds. Very sour and generally considered bitter and essentially inedible fresh — the high acidity can even cause stomach upset if eaten in quantity. Grown almost entirely for rootstock and ornamental value rather than for its fruit, though it is occasionally used in marmalade or as a flavoring.
- Propagation
- Propagated overwhelmingly from seed — the standard nursery method, producing generally true-to-type, thorny, cold-hardy seedlings. This is the single most widely used cold-hardy rootstock in the world, onto which less-hardy citrus scions (lemon, orange, mandarin and others) are grafted specifically to extend their growable range into colder climates — a role that far exceeds any use of the species for its own bitter fruit.
- Pollination
- Most Citrus SELF-FERTILE (many parthenocarpic/seedless)
The edible parts listed above are a starting point, not a field guide. Identify a plant with certainty — ideally against a local authority — before eating any part of it, and read the full disclaimer. Spotted something wrong? Report it.
Growing guide
Fertilizing. Tolerant of a wide range of soils — light, medium or heavy — and generally low-input once established; no serious pest or disease problems are reported. A well-drained site matters more than heavy feeding, since the shallow root system does not tolerate waterlogging.
How it spreads. Unlike most single-trunked, non-suckering Citrus, this species has documented escaped and naturalized populations in the southeastern US — for example forming dense thickets along floodplains such as Robeson Creek in Chatham County, North Carolina — and is flagged as weedy or invasive by bodies including the North Carolina Invasive Plant Council. Further north, winter cold appears to keep it in check.
Growing tips. The benchmark for cold-hardy citrus — deciduous (unlike most evergreen Citrus) and capable of surviving well below 0°F/-18°C when dormant, which is exactly why it is the world's most widely used rootstock for extending the range of less-hardy grafted citrus. Rated here to zone 6, which is where it is reliably hardy; it does grow in the warmer parts of zone 5, but sources agree it wants a sheltered spot there and is not dependable in the colder half of that zone. It is also documented as tolerant of citrus greening (Huanglongbing/HLB) and other major citrus diseases, a trait actively studied for breeding disease-resistant citrus. Very thorny — sharp, numerous spines cover the bright green stems, making it useful as a security hedge but awkward near foot traffic. Flowers appear before or with the leaves in early spring, ahead of most other citrus.
Grow journal
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