118 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



Black walnut (Fig. 105) usually grows tall and straight in 

 woodland areas, reaching a height of 70-90 feet and having a 

 branch spread of 50-70 feet. An occasional tree may reach a 

 height of 150 feet. The trunk may be clean of branches to a 

 height of 40-50 feet. However, in open areas or as specimen 

 trees, black walnut usually produces a short trunk with a broad- 

 spreading crown. The twigs are hairy at first but later become 

 smooth and orange to dark brown. 



Black walnut is one of the last trees to leaf out in the spring 

 and one of the first to lose its leaves in the fall. The large com- 

 pound leaves (Fig. 105 inset), 1-21/2 feet long, are made up of 

 5-11 pairs of oblong to lance-shaped, short-stalked, leaflets, and 

 usually there is one long-stalked leaflet at the tip. Sometimes the 

 terminal or tip leaflet fails to develop, leaving an even number 

 of leaflets. The irregularly toothed leaflets are 214-5 inches long 

 and each leaflet has a pointed tip and a rounded base. Male and 

 female flowers are borne separately on the same tree, the male 

 flowers in pendulous catkins and the female flowers in small, 

 inconspicuous clusters. The large- globe-shaped, rough, fleshy- 



Fig. 10.5.— The slow- 

 growing black walnut is 

 used occasionally as a 

 specimen tree or for its 

 highly prized nuts. The 

 large, compound leaves 

 (inset) are made up of 

 .5-11 pairs of leaflets 

 and usually have a sin- 

 gle terminal leaflet. 



