For anyone planting a new wood, shelterbelt or restocking a felled site on ground that is wet, heavy or thick with grass and bracken. Mounding gives each young tree a raised, weed-free spot to root in, which can make a real difference to how many survive.
An excavator works across the site, digging a scoop of soil and turning it over beside the hole to form a mound, typically in rows at the spacing of your planting plan. The turned turf smothers the grass under the mound and lifts the planting position above the wettest soil.
There are variations. Inverted mounds turn the turf upside down and cap it with mineral soil; hinge mounds leave the turf attached on one side. On very wet sites the holes are sometimes linked into shallow drains. The contractor will suggest what suits your soil.
The mounds are left to settle before planting, and trees are planted into the top or the shoulder of each mound.
Mounding is done ahead of the planting season, usually from late summer through winter, so the mounds have a few weeks or months to settle before bare-root trees go in between November and March.
On restock sites it follows felling and brash clearance. Very wet spells make the work slow and the mounds slump, so a drier window in autumn is ideal where you can get one.