Din cate vad eu pe acest link "heeling" este o pre-plantare. Pentru a evita uscarea radacinilor datorita caldurii/secetei, se imbiba radacinile cu apa si se plaseaza intr-o groapa asa cum arata pozele; se indeasa ( de unde si termenul "heeling') si se acopera cu pamant pana la plantarea definitiva.
Fragmentul postat presupun ca da instructiuni privind fixarea unei distante adecvate intre santuri.(trenches)

http://www.extension.umn.edu/distribution/naturalresources/D...

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Note added at 36 mins (2008-04-19 22:29:18 GMT)
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Left: Select a shady spot and dig a V-shaped trench in soil that is moist. Right: Open a bundle of trees and spread the roots out evenly along one side of the trench.
Left: Stamp down the soil for a firm covering. Right: Water the heeled-in trees each morning. Drench well with water.

When your trees are delivered: (1) Pick them up promptly upon notice of arrival; (2) Give them a good soaking without delay (do not leave trees in the wrapped package more than two or three days, because they may dry out, heat, or mildew); and (3) If you are not going to plant the trees for several days, "heel in" the trees in a trench, preferably in a cool, shady place (figure 2). Make the trench deep enough for the entire root system and part of the lower stem.

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Note added at 17 hrs (2008-04-20 15:03:54 GMT)
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Figure 2. Heeling in seedlings to protect roots.