Hardy Orange
Poncirus trifoliata
As its name suggests, the hardy orange is closely related to oranges, lemons, limes, and other citrus, but it is unusual in shedding its leaves and having fruits covered with soft, velvety hairs. Also unusual is that the tree is resistant to frosts that would be fatal for other citrus. This tolerance of cold makes hardy orange useful as a rootstock onto which other citrus can be grafted. The resulting tree, with two genetic identities, is better able to withstand a winter freeze.
Botany Break-Out
The hardy orange is armed with massive thorns that provide a significant deterrent to hungry herbivores. Experiments show that these thorns begin to grow like normal shoots, but then their genetic program gradually tapers off, leaving nothing but a sharp pointed tip.
