Growing Poplar and Willow Trees on Farms, National - FAO

At the tenth year following planting, trees that are too close or growing
poorly can be removed <strong>and</strong> used for fodder <strong>and</strong> firewood. The gaps are then
filled with new trees. This process will be repeated every 10-15 years,
depending on tree growth, giving a sustainable st<strong>and</strong> of protection planting.
Root growth
One point about pruning these trees – remember what is happening to
the root system below ground when timing the first branch
pruning. Joint excavations by AgResearch <strong>and</strong> HortResearch staff have
determined poplar root growth at Ballantrae, AgResearch’s hill country
research station near Woodville. At five years after planting from poles,
poplar roots showed negligible growth (in terms of mass <strong>and</strong>
distribution) compared with those at seven years, <strong>and</strong> particularly at nine
years.
Consider the extent of pruning as well, <strong>and</strong> which parts of the canopy
should be pruned. It is important to maintain a good balance between
the tree canopy <strong>and</strong> the root system.
Pruning poplars for timber
Once established poplars can be pruned so that they develop as a timber
resource as well as providing those other functions: stabilising soil <strong>and</strong>
providing stock shelter <strong>and</strong> shade.
<strong>Trees</strong> put on regular growth increments each year. Whorls describe the
position on the stem where a group of branches develops. A new whorl
forms each year, so the branches at a whorl represent one year’s lateral
branch development. As a guide it is advisable to retain three years of green
crown (three major whorls) to sustain an acceptable rate of growth.
Removing side branches <strong>and</strong> extra leaders promotes tree stem growth, <strong>and</strong>
while root response to pruning is not known, the stem response suggests that
root development is not greatly retarded.
Begin form-pruning trees at around 4 or 5 years after the poles were planted,
depending on vigour <strong>and</strong> local wind exposure. At the first pruning reduce the
leaders to one strong leader, <strong>and</strong> remove any large ramicorns (steeply angled
vigorous branches), as these are likely sites for splitting in old trees. Two
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