Written by Dusty Hancock, Extension Master Gardener℠ Volunteer in Chatham County
The ‘dinosaur plant’ is what my grandchildren call this gnarly looking plant growing up in the fence rows around our property. With its large, and ferocious thorns, it certainly looks a bit mean and primeval!
There is a debate among taxonomists on whether this species should be placed in its own genus, Poncirus, or included in the genus Citrus. Morphologically, trifoliate orange is distinct from other species and cultivars of Citrus by the fact is deciduous (loses its leaves in the winter), has compound leaves (a group of multiple leaflets instead of a single leaf attached to the twig with an axillary bud), and has pubescent fruit (fuzzy like a peach). Genetic analysis suggests it is nested within other Citrus species, but some taxonomists still recognize it as Poncirus trifoliata rather than Citrus trifoliata.
We recognize it not only by those thorns but the gentle citrus scent when the white blooms appear in the spring. These blooms develop into lime-sized fruit in the summer. By early fall those ‘limes’ have turned into a small yellowish-orange fruit. They provide little dots of color in our fencerows as their leaves drop and their visibility is increased.
The ripe fruit has a tough rind, a lot of seeds, and much less pulp than in cultivated citrus. In the US, the fruit and rind are occasionally used in the manufacture of marmalade or citrus flavoring. They have a low toxicity if consumed but in large quantities their acidity has been known to cause stomach pain and nausea. Some people do suffer temporary contact dermatitis if exposed to the plant. They are a staple in East Asian traditional medicines.
They were originally imported from China to provide rootstock for commercial seedless navel orange groves in California back in the late 1800s. They are also great barrier plantings (even if you don’t have hungry dinosaurs). One cultivar, ‘Flying Dragon’, has been used to control students jaywalking at Oklahoma State University - Stillwater for over 50 years. However, the North Carolina Invasive Plant Council considers it an invasive species, so it is probably best to avoid further plantings. For more information, see the NC Extension Gardener Plant Toolbox.
