Poplars were first grown in New Zealand in the 1830s. They were brought in as ornamental trees and for shelter. Lombardy poplar (Populus nigra ‘Italica’), eastern cottonwood (P. deltoides) and silver poplar (P. alba) were among the early introductions. Lombardy poplar, with its column-like form, was especially favoured – it was often planted to mark boundaries and river fords as it could be seen from a distance.
In the 1930s the New Zealand Forest Service imported more poplar species to investigate their timber potential.
During the latter half of the 19th century, Lombardy poplars were often planted near central North Island Māori villages (pā) associated with the prophet Te Kooti. In about 1880 he planted a poplar stem at Tamatea pā to symbolise his life taking a new pathway – away from war and towards peace. Members of the Ringatū church, which he founded, likened the upright branches of this poplar to the uplifted hand – the central symbol of their faith.
Poplars for erosion control
From the 1950s onwards, poplars, along with willows, were increasingly used to stabilise slopes in the central North Island. They are fast growing on moist, fertile sites, and are easily grown from stem cuttings. Trees are planted at wide spacings (25–150 stems per hectare), so pasture can continue growing between them.
Between 1950 and the late 1970s soil conservation scientists imported about 200 poplar varieties from Europe, America and Asia for research and breeding. This research stock proved invaluable in the mid-1970s, when two virulent poplar rusts devastated mature stands of poplar throughout the country. Resistant strains, selected from plants held at the Soil Conservation Centre in Aokautere, near Palmerston North, were distributed through the country to replace diseased poplars. The poplars that now grace erosion-prone hillsides are most likely to be hybrid clones of various parentages or the Chinese poplar (P opulus yunnanensis).
Willows were also an early import. Weeping willow (Salix babylonica) cuttings, reputed to be from alongside Napoleon’s grave on St Helena, were planted at Akaroa in 1839. Other early introductions included S. fragilis, S.alba, S. cinerea and S. viminalis.
River bank plantings
Willows have been extensively used for river control, and crack willow was the main species used for nearly 100 years. At first, little attention was given to the problems that could occur as the willows grew. Branches readily break off in storms and floods and float downstream. If they take root on sandbars and banks they can soon choke the waterway. When willow growth becomes too dense in river channels, it needs to be cleared to prevent flooding.
There are a few willow clones that do not have brittle branches, and are more suitable for stabilising river and stream banks. Willow hybrids and hybrid poplars are used for river control work, as well as for soil conservation on hill slopes.
Shelter and fodder
Selected poplars and willows are also used for fast-growing shelter belts, especially around orchards and market gardens. The main species used are Salix matsudana and its alba hybrid, and black poplar (P. nigra) hybrids are also common.
Willows and poplar foliage can provide nutritional fodder for stock during droughts.