Box elder vs Red maple

Invasive. Female trees shed winged seeds from September to March, the wind carries them far, and a felled or damaged tree resprouts from the stump. In Central Europe it mainly takes over river floodplains and softwood riverside forests, where it crowds out willows, poplars and other native trees; seedlings also settle in cracks of walls and paving. In Hungary the government decree on the protection of woody plants lists it as an invasive species: it may not be planted, or used as a replacement tree, in public spaces and other areas in public use. The annex's exception for horticultural cultivars is marked in the current text only for tree of heaven and green ash, not for box elder, so the variegated cultivars are not exempt either. Conservation authorities advise against planting it in gardens as well. Other problems: the wood is soft and brittle, branches break in wind and snow, and the tree is short-lived; the pale leaf margins of variegated cultivars scorch in hot, dry spots. The tree is a favourite host of the fall webworm; in its North American homeland box elder bugs (Boisea trivittata) build up on female trees and move into houses in autumn. Pollen from male trees is strongly allergenic.

On the often calcareous, alkaline garden soils of Central Europe the leaves turn yellow between the veins (manganese and iron chlorosis), growth stalls and the autumn colour fails; the same happens on persistently dry soil. In hot, dry summers the leaf edges scorch without watering. Verticillium wilt can be fatal, and aphids, leafhoppers, scale and borers also occur. The wood is rather brittle, wind and ice can break branches, and it is not a tree for a windy site. The shallow, dense root mat can lift nearby pavements and driveways, and little else grows beneath it.