Recently, I received an email with a picture of a gnarly shrub with serious, long sharp spikes and leaves with three leaflets. It is a shrub or small tree, green throughout including stalks, branches and thorns. The subject line asked, “Ozark citrus?”
The answer is yes and no. But there is actually a Citrus species that grows wild in the Ozarks! It’s known by the common names trifoliate orange, Japanese bitter orange, Chinese bitter orange, trifoliate citrus, hardy orange, and plain ol’ bitter orange.
The plant is one among the 25 species of Citrus, almost all of which are of tropical origin from Asia, Australia, and New Caledonia. The genus Citrus is the most widely grown group of tropical fruit trees in the world and includes lemons, limes, oranges, grapefruits and all their varietal iterations. They have been cultivated for so many centuries that their exact origin remains unclear. Over the last 20 years, new genetic information begins to unravel the origins of Citrus trees and their many hybrids.
From 1838 until 2009, the naturalized spiny “hardy orange” was known as Poncirus trifoliata, but in 2009, genetic data showed it belongs in the genus Citrus and is now called Citrus trifoliata. It is on the list of non-native invasive plant species of concern to natural areas in Arkansas.
It occurs in most counties in Arkansas and much of the Southeast. Introduced to Western horticulture from China and Japan in the 18th century, this hardy citrus is armed with formidable spines, and when planted close together, makes an impenetrable fence. The small, round hairy fruits produce viable seeds, so will spread on their own.
The fruits are so incredibly bitter, or as one author described them in the 1830s, “ungrateful to the taste,” they make lemons taste sweet. Tennessee nurseryman Don Shadow’s recipe for poncirus-ade is take a barrel of water, add a barrel of sugar, and one hardy orange fruit. You get the point.
In Traditional Chinese Medicine, the dried immature fruits are called goujiu, and are used to treat gastrointestinal and cardiovascular diseases. The dried fruits are also used in Korean and Japanese folk medicine.
Crosses between this and other types of citrus produce rootstocks used for grafting orange and lemon varieties. New genetic information is revealing the genes that make this wild, non-native, hardy citrus cold tolerant. Now, if they can only do something about the flavor.