ABSTRACTS

SHURTLEFF, M.C. 1979. Trees for a city environment. Grounds Maintenance 14(7): 44, 46, 48, 50.

To grow well in spite of the hazards of city life, a tree must be hardy and disease-resistant. It must withstand air pollution and soil compaction caused by pedestrian or vehicular traffic. It must also be easy to maintain, with a growing habit that conforms to available space. This is the last in a series of articles listing the best trees for a city environment. This article describes the characteristics and utility of the following trees: oak, pear, pecan, redbud, sassafras, serviceberry, silktree, Sophora, sourgum, sweetgum, sycamore, tulip tree, yellowwood, and Zelkova.

SMITH, R.C. 1979. Effects of air pollution on landscape plants. Grounds Maintenance 14(6): 59, 79.

Knowing the kinds of air pollution and their effects on landscape plants can help the grounds manager protect vauable plant material. Common air pollutant gases and their effects: 1) sulfur dioxide — ivorycolored foliage; bleaching; chlorosis (loss of normal green color); 2) hydrogen fluoride — same as above, quickly affects Prunus, Quercus, Abies and Pinus; 3) chlorine — interveinal chlorosis; upper leaf surface has silvery appearance; 4) nitrogen oxides — toxic range: 25 ppm or greater, (lower levels may be useful as fertilizer), at toxic levels, leaves have brown margins and black spots; 5) smog — bleached appearance; drying, brown color; 6) ethylene — in low concentrations, has strong hormonal effect on plant material, at toxic levels, epinasty, chlorosis and leaf drop will occur; and 7) hydrogen sulfide — leaf scorch on young foliage, older, mature foliage usually left uninjured.