The scientific name is Poncirus trifoliata , and it is classed in the family Rutaceae . Genuine citrus fruits that we eat are also placed in the family Rutaceae, which is why trifoliate oranges are considered closely related. The edible citrus fruits are in the genus Citrus . Oranges, for example, are Citrus sinensis , and lemons are Citrus limon . Although trifoliate orange is in a different genus from regular citrus trees, it is related closely enough to use as rootstock for various Citrus species.
Trifoliate orange is hardy to zone six, which includes most of southern Missouri.
They will grow in some locations in zone five, but can be killed when temperatures approach -20 degrees. In the spring they produce white flowers. The fruits resulting from these flowers are classed as a modified berry, known as a hesperidium, the same as edible citrus. This is readily seen when you cut it open, with sections that are identical to oranges or grapefruits. These plants also produce many thorns.