{"id":25028,"date":"2015-08-06T02:31:22","date_gmt":"2015-08-06T06:31:22","guid":{"rendered":"https:\/\/greenblue.com\/how-much-soil-do-urban-trees-need\/"},"modified":"2024-03-21T12:53:37","modified_gmt":"2024-03-21T12:53:37","slug":"how-much-soil-do-urban-trees-need","status":"publish","type":"post","link":"https:\/\/greenblue.com\/na\/how-much-soil-do-urban-trees-need\/","title":{"rendered":"How Much Soil Do Urban Trees Need?"},"content":{"rendered":"

Trees need appropriate amounts of loose, moist, well aerated, and uncompacted soil in order to mature\u00a0in the urban environment. These conditions enable the tree’s roots to obtain nutrients, oxygen, and water – all essential for healthy tree growth. After defining in detail the soil requirements needed for healthy root growth<\/a> in last week’s post, we will now discuss how much uncompacted soil trees need to thrive and reach maturity.<\/p>\n

In addition to the nutrients that trees obtain from soil through their roots,\u00a0they also need oxygen and water that occupy the voids between soil particles. These voids are abundant in\u00a0uncompacted\u00a0soil, however, soil in urban areas is usually compacted to provide structural integrity for paved surfaces – making void space between soil particles nonexistent.
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“Trees in urban areas are frequently observed either failing in the face of\u00a0hostile growing conditions, or surviving and causing damage to pavement”<\/em><\/strong><\/p>\n<\/blockquote>\n

If soil alone is depended on as a structural material and required for the load-bearing of\u00a0buildings, vehicles, and\u00a0pedestrians; it will be compacted to the point that air and water are excluded and a totally insufficient space for root growth will be available.<\/p>\n

Trees planted in unsuitable urban tree pits are usually surrounded by compacted soil which often leads to the roots seeking out the space between the compacted soil and the paved surface above, where air and water are present. This then causes pavement heaving.\u00a0If tree roots can’t grow into surrounding soil, they continue to grow until they have filled the space that’s available.<\/p>\n

When a tree’s need for nutrients, water, and air can no longer be met, the health of the tree suffers and the tree begins to decline and eventually die. Trees grown in these conditions hardly ever reach maturity and do not provide the many benefits that healthy trees offer<\/a>.<\/p>\n

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“The availability of space for tree roots to develop is crucial to a tree’s\u00a0health.\u00a0<\/strong><\/em>A growing tree’s roots will extend far into the surrounding soil\u00a0to\u00a0<\/strong><\/em>more than twice the diameter of the mature tree’s canopy”<\/strong><\/em><\/em><\/div>\n<\/blockquote>\n
This challenge creates a fundamental conflict for trees in paved areas.\u00a0Careful consideration needs to be taken regarding the above and below ground space to ensure that each tree has what it requires to reach maturity.\u00a0The old method of providing a tree pit area the size of the pavement opening is clearly insufficient and\u00a0results in a lifetime of costly pavement repairs and\/or commits the tree to an untimely death.<\/div>\n

So, how much uncompacted soil do trees need to be healthy and reach maturity?\u00a0Various methods of determining required soil volume may\u00a0be used to calculate the approximate below ground space that a tree should need for healthy root growth.<\/p>\n

Mature Canopy Method<\/h3>\n

Likely the simplest method of calculating soil volume, is estimating the projected mature tree canopy diameter and multiply it by a depth of 2ft. GreenBlue offer a\u00a0tree pit soil calculator<\/a>\u00a0that will easily provide these calculations for you.<\/p>\n

As a general rule:<\/p>\n