88 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



short female spikes, produced separately on the same tree, stand 

 on slender, wooly stems. The -'4.- to IV-i-i^ich-long, dark chestnut- 

 brown acorns are one-third to one-half covered with a thin cup 

 supported on a V-i^i^ch-long, stout stalk. The pale brown trunk 

 bark is deeply furrowed and plated. The branches are unusual 

 because of the ribbed and corky formation of bark. Bur oak 

 grows more rapidly and is more easily transplanted than white 

 oak. It is highly prized as a shade and ornamental tree. 



The other native oak species in Illinois are used occasionally 

 for shade or specimen purposes. Species such as black oak (Q. 

 velutina) , chinquapin oak (Q. muhlenbergii) , scarlet oak {Q. 

 coccinea), basket oak (Q. prinus) , shingle oak (Q. imbricaria) , 

 and willow oak (Q, phellos) are available at some commercial 

 nurseries. 



Although oaks are occasionally attacked by insects, including 

 periodical cicada, oak kermes, leaf miners, and gall-producing in- 

 sects, the amount of damage caused is usually limited or localized 

 and does not warrant annual treatment for insect control. Oak 

 wilt is the only widespread and destructive disease of oaks in 

 Illinois. However, this fungus disease occurs mainly among trees 

 in forest and woodlot plantings and generally is not a serious 

 threat to the sparsely planted oaks in ornamental plantings, espe- 

 cially where oaks are not growing close enough to one another 

 for their roots to become grafted. Spread of the oak wilt fungus 

 occurs most readily through grafted roots between adjacent 

 trees. 



Oak is the principal hardwood tree used in the wood indus- 

 try. Most species of oak have strong, close-grained, tough, dur- 

 able wood that is suitable for a wide variety of uses, including 

 fence posts, railroad ties, mine timbers, barrels, furniture, inter- 

 ior finishing, and fuel. 



Osage Orange 



Osage orange {Madura pomifera) (Fig. 82), sometimes 

 called bow wood or hedge tree, with its round-topped crown of 

 spiny, uptilted, spreading branches, grows to a height of 30 feet 

 in the open and 50-60 feet when crowded. This tree is widely 

 distributed in the United States. However, its native range is 

 from southern Arkansas and Oklahoma southward into Texas. 

 Although this tree has been used extensively for farm hedges 

 throughout the state, it prefers rich bottomland. 



The oval, alternate leaves (Fig. 82 inset), each with an 



