Citrus 942

US-942 began life as a rootstock, bred by the USDA and released in 2010 after years of Florida field trials, a careful cross of the Sunki mandarin and the curious Flying Dragon form of trifoliate orange, Poncirus trifoliata. As a rootstock the record is stellar: compact, productive trees, strong resistance to Phytophthora and tristeza virus, and better tolerance of citrus greening than most, which is why growers across the citrus belt have come to trust the number.

What surprised everyone is the fruit on the rootstock itself. Where most trifoliate hybrids carry the bitter trifoliate aftertaste as a family curse, US-942 mostly sheds it. The little fruits ripen bright orange inside and out, not much larger than a ping-pong ball, thick and soft in the skin like a small mandarin and easy to peel, with juice that runs somewhere between the sweet citrus of a calamondin and the tart brightness of a kumquat, and few seeds. Herschel of Madison Citrus, who knows the tribe as well as anyone, calls US-942 "one of the best-tasting trifoliate hybrids there is," and we would not argue.

In the garden, grow US-942 in full sun and sharp, well-drained soil, in the ground through the warmer zones or in a large container to overwinter farther north. Hardy, disease-resistant, compact, and productive, the tree suits the collector of unusual citrus and the grower who wants a tough, good-tasting fruit off a plant that asks little. A rootstock that turned out to be worth growing on its own merits.