80 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



duced separately on the same tree or on separate trees. The 

 flowers of boxelder are regularly produced on separate trees. 

 The U- or V-shaped fruit, known commonly as "maple keys," and 

 composed of two single-winged seeds, is produced in late spring 

 on red and silver maple and in autumn on sugar and black maple 

 and boxelder. The bark of maples varies from light gray to dark 

 brown or black. It is fissured and rough on boxelder, sugar, and 

 black maple and scaly on red and silver maple. 



The rapidly growing Norway maple (A. platanoides) , with 

 its broad, dense head, dark bark, and foliage similar to sugar 

 maple, is planted widely along streets and in lawns and parks. 

 However, its dense shade prevents good growth of lawn grasses. 

 It may reach a height of 90 feet with a branch spread of 40-60 

 feet. The slow-growing sugar maple is planted extensively as a 

 street, lawn, and specimen tree and is also a woodland tree. It is 

 resistant to injury from ice and wind. Several varieties of sugar 

 maple, especially those of columnar habit, are well adapted for 

 planting along narrow streets. The brittle wood of the rapidly 

 growing silver maple and boxelder is easily broken by wind and 

 ice. Silver maple also may be severely damaged by infestations 

 of cottony maple scale, and the leaves are frequently deformed 

 by the maple bladder-gall mite. Verticillium wilt is the most de- 

 structive disease of maples and it most frequently affects Norway 

 and sugar maples in Illinois. 



Silver maple and boxelder have relatively little economic 

 value for wood products. Sugar maple has hard, fine-grained, 

 hea\y wood. It is one of the most valuable Illinois hardwoods and 

 is used in the manufacture of numerous products including furni- 

 ture, flooring, farm implements, muscial instruments, boxes, 

 crates, toys, trunks, and veneer. The highly decorative "birdseye" 

 maple used in paneling for walls, cabinets, and beds, and the 

 ornamental "curly" maple used extensively in cabinets, are ob- 

 tained from sugar maple. Maple sugar and maple syrup are 

 made from sugar maple sap and can be made from boxelder sap. 



Mountain Ash 



American mountain ash (Soi^bus americayia) and European 

 mountain ash, sometimes called rowan tree, {S. aucuparia) (Fig. 

 76) are small, round-headed trees which grow to heights of 25-35 

 feet. They are attractive in ornamental plantings because of their 

 small size, compound leaves, white flowers, and showy orange to 

 red fruits. 



