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Native soil variability means that a given tree species - although hardy to this climatic zone - may not excel equally at all locations in the city. Native plants growing on site are often an indicator of soil suitability for landscape plants. Plants should be chosen that tolerate local soil conditions.  If you are unsure of soil conditions on your growing site, or if you are having difficulty establishing plants, a soil test from an accredited lab may help.


Acidity is measured using the pH scale, which runs from 0 (extremely acidic) through 7 (neutral) to 14 (extremely alkaline).  Fairly acidic soils with pH 5.5, though suitable for evergreens, may result in pale green leaves on some deciduous hardwoods. The elemental balance that these hardwoods require is more readily available at neutral pH levels (pH 6.5 – 7.5). Pine trees will thrive in sandy, acidic soils and may struggle in alkaline, clay gumbos.




High water tables may also influence trees because plant roots require oxygen. Combine a high water table with slow draining clay soils and tree roots may become oxygen-starved during extended rainy periods or under excessive irrigation. Stunted new growth or tree death from drowning may result.



Salt Damage




Compacted urban boulevard soils often suffer from salinity problems, due to a combination of added salt from winter road maintenance and lack of drainage to flush the salts away.  As salinity increases, it becomes more difficult for many plants and trees to thrive, as the salt prevents plant roots from taking up water.   





Soil Compaction


Current urban engineering practices for new roads and subdivisions involve stripping the topsoil from the land, laying in all services and road bases, then replacing the topsoil before completing landscaping.  This promotes a layer of severely compacted subsoil called hardpan, which is often so compacted that plant roots cannot penetrate it at all.  As boulevards are driven over and sidewalks replaced, even the topsoil will eventually become compacted, preventing plant roots from spreading properly and accessing oxygen and water.  Regular aeration will help alleviate compaction, as will amending heavy clay soils with sand to improve drainage and break up hardpan.

Last updated: 12/3/2012 12:33:45 PM