Trifoliate orange

Trifoliate Orange (Poncirus trifoliata) is a member of the genus Rutaceae which includes the citrus family.

It is also known as the Japanese Bitter Orange. It is not a true citrus, but is sufficiently closely related to allow it to be used as a rootstock for citrus.

Although semi-evergreen, the plant is fairly hardy and will tolerate moderate frost and snow. Because of the relative hardiness of Poncirus, citrus grafted onto it are usually hardier than when grown on their own roots.

Poncirus is recognisable by its trifoliate leaves and large spines. The flowers are larger than those of true citrus and closely resemble clemetis montana. They are said to be scented but I have never detected any scent. As with true citrus, the leaves have a spicey smell when crushed.

The fruits are green, ripening to yellow and about the size of small plum. They are not edible although when dried and powdered, they can apparently be used as a condiment.