This is Poncirus trifoliata, also known as Trifoliate Orange, Citrus trifoliata, Contorted Flying Dragon, Japanese Hardy Orange, and Bitter Orange. This hardy orange tree can grow up to 6 feet tall, or it can be grown in a container where it will probably not get that large. It likes to live in the sun but can do rather well in partial shade. The white blossoms are very attractive and are out in full force from late Spring until early Summer, but the real show stopper here are the spiky contorted branches which resemble a flying dragon if you squint and use your imagination just right. This tree is even interesting to look at in the Winter. This tree is very popular with the birds, bees and butterflies. This is a larval host plant for the Giant Swallowtail butterfly. The fruit can be eaten but it is kind of a cross between a lemon and a grapefruit. The most common uses are as marmalade, dried as seasoning, or juiced. The juice is then diluted and sweetened for a drink. USDA Hardiness Zones 6 to 10.