6 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



Some kinds of trees have disadvantages that make them 

 somewhat undesirable for widespread use, inckiding suscep- 

 tibility to attack by diseases and insect pests, soft or brittle 

 wood that is easily damaged by wind and ice, fruits and seeds 

 that are large, messy, smelly, or otherwise obnoxious, and abun- 

 dant shedding of twigs and small branches. Some examples of 

 these conditions are killing of Lombardy (Fig. 9) and Simon pop- 

 lar by Cytospora canker or by borers, breaking of Siberian elm 

 branches by wind and ice, cracking of the trunks of London plane 

 trees because of low temperatures (Fig. 10), and production of 

 ill-smelling fruit by the female ginkgo. The production of fruit 

 by the mulberry, which as previously mentioned attracts birds, 

 can also be an undesirable characteristic. Since this fruit is soft 

 and decomposes rapidly when ripe, it is messy on walks and at- 

 tracts flies and other insects. 



Seek Professional Advice 



Before deciding what species to buy it is desirable to get the 

 advice of a person familiar with trees. Nurserymen, arborists, 

 and landscape men are familiar with the various species of trees, 

 the purposes for which they are used, and the environmental con- 

 ditions under which each thrives. Such individuals can offer val- 

 uable advice on selecting the species or kind of tree most suited 

 for a given location and purpose, when and how to plant, and 

 how to prune the newly planted tree. Also they are familiar with 

 the growth rates of trees, relative sizes and shapes at maturity, 

 and the requirements for best growth. These growth require- 

 ments include soil type and acidity, water needs, and whether 

 certain trees grow well in open areas or need partial protection 

 from wind and sun. 



Nursery Trees and Wild Trees 



Trees obtained from commercial nurseries may be grown in 

 the field (nursery grown) or in impervious containers (container 

 grown). Container-grown trees are sometimes kept in the con- 

 tainers for several years, which may cause the roots to become 

 restricted, intertwined, and twisted. Purchasers should avoid 

 this condition : it may be so serious that the trees grow poorly 

 or do not survive when planted. 



Nursery-grown trees have many advantages over wild trees 

 taken from woodland or field locations. Nursery-grown trees are 

 top pruned to produce good shape and root pruned to produce 



