Citrus trifoliata

Hardy Orange is an introduced perennial woody shrub in the Citrus Family (RUTACEAE). It occurs statewide in Alabama. Hardy Orange grows in pastures, on fence rows, in vacant lots, and along streams. It is usually a multi-trunked shrub with green stems. The stems are armed with large thorns. Hardy Orange has alternate, deciduous, trifoliate leaves. In the spring it produces showy white flowers with five petals. These are followed by a hairy fruit that is about the size of a golf ball. The fruit becomes yellowish orange when it matures. The fruit is very seedy and tart, but can be used to make drinks and marmalade. Processing the fruit often leaves a resin-like residue that is difficult to remove. Hardy Orange is used as a root stock for grafting other citrus species. It is the most cold hardy of the citrus species, and other species are hardier when grown on this rootstock. It has also been widely planted as a hedge to contain livestock or prevent trespassing. Many birds prefer to nest in this species as it is difficult for many predators to reach their nests because of the spines. Hardy Orange can easily be grown from seed, and is often available through nurseries. Flying Dragon is a cultivar with curved thorns. Citrange is a hybrid between this species and the Sweet Orange (Citrus sinensis).--A. Diamond   

Known as Poncirus trifoliata (L.) Raf. in most floras and manuals.