Toppling – advice and insights
Author not published, New Zealand Tree Grower August 2006.
Toppling is when young trees begin to lean, due to poor root anchorage. It usually occurs when the trees are two or three years old. It can be a problem on heavy soils, especially after prolonged rain. If left uncorrected, the resulting trees will have butt sweep – a permanently curved lower stem or butt log which should be your most valuable log but only if it is straight – and possibly some stem sinuosity – twisted or unbalanced shape, again devaluing the butt log. The trees can also be more prone to windthrow later in life.
On radiata sites, planting aged cuttings will significantly reduced the incidence of toppling. The thinning out of the mid-crown area of two and three-year-old trees to reduce the sail area is also a useful preventative measure. If toppling has already occurred, a number of studies have shown that corrective measures are only economic if the problem is severe.
For small trees, the simplest method is to use a sod firmed down against the down-wind side of the tree. Larger trees may need to be tied back. When tying, it is best to use two ties of untreated twine tied to a strong branch, not the trunk, and fixed to the ground with small untreated pegs – manuka is ideal. As a last resort where toppling is severe, cutting off the stem above the lowest whorl and allowing a branch to take over as a leader can often save the situation.