Is it thumbs up or thumbs down for tree-of-heaven (Ailanthus altissima), now standing out among the general greenery for the mops of yellowish or orangeish seeds capping its stout branches? Thumbs ...

Growing and spreading rapidly in even the poorest soils and with little water, tree of heaven is, despite its name, the very definition of "weed tree." It can cause allergies and irritate the skin, ...

Although sometimes growing in stately elegance, a tree-of-heaven, in center background, is a weed tree that shows up everywhere, from forests to cracks in urban pavement. (Lee Reich) Is it thumbs up ...