Tree of Heaven, also known as Ailanthus altissima in the scientific world, is an extremely hardy tree from Asia, and the tree mentioned in the book A Tree grows in Brookland It is charactarized by its large clumps of compound leaves and huge orangeish flowers at the end of its stems. In China, it forms large, majestic forests. Outside its natural habitat, it is far from heavenly, and is becoming a serious weed in many areas, such as California, where it was brought in by Asian immigrants in the 18th century. It invades riparian areas and crowds out most other plants. It does this by reproducing aggresively by means of suckers; one of these trees may create a thicket of hundreds of saplings in a few years. I don't recommend planting this tree unless you are in East Asia; if you do plant it outside its native range, your neighbors will curse you when their lawns and gardens are filled with many suckering shoots of this plant.