Why is planting depth so important?

11 Nov 2015

Now that the planting season is in full swing I thought I would re-open the topic of planting depth. Trees are more often than not planted too deeply. In nature a seed lands on the soil from the tree above and germinates with the root going downwards and the shoot going upwards, it’s as simple as that! Roots and shoots are two different mechanisms so it is totally against the rules of nature to heap soil up and over the stem. When this happens the roots are deep within the compacted layer of soil that is least oxygenated and often wet. Tree roots need three vital ingredients to grow and thrive, namely water and oxygen blended in measure and a soil temperature of between 10 and 20 degrees Celsius and these conditions are most likely to occur in the top metre of the soil profile.

A stem baring no roots buried below ground will make the tree unstable in windy conditions with a tendency to rock around in a circle producing a gap between the stem and the existing soil. Imagine blowing a pencil standing on its end off a table, dead easy! Try and do the same with a wine glass and you won’t be able to do it! A well anchored tree is like the wine glass with its roots on the surface spreading out laterally like spokes of a wheel to cover a surface area to hold up its trunk (stem) which in turn supports its crown (cup). Planting a tree deeply can greatly hinder this process.

Quite often root balled trees are lifted with the downward action of the blades heaving soil up and over the stem above ground so the tree is several inches deep before you even get round to planting it. Planting trees a few centimetres proud of the soil line can solve this one. Below ground anchoring systems on top of the roots can also mean your tree is planted deeper that it should be. Digging a hole much deeper than the height of the root system can mean that the roots sink gently into the disturbed ground after planting which is another thing to avoid. Generally speaking it is good to dig a hole twice the width of the root system but the same depth as the root system.

To make this problem totally transparent we offer a chargeable service called the Barcham Line whereby the tree comes with a painted mark at its base. It you can’t see this mark after the tree is planted you know the tree is planted too deep! Trees heave themselves a little bit out of the ground at maturity and you can notice this by seeing their root system diving into the ground from above ground level. You don’t see trees with tubular stems and no basal flare rising from the ground very often!

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