Poplars have been planted in New Zealand for
well over 150 years and are now an integral
part of the rural landscape. Historically,
poplars have been planted for soil conservation,
as wide spaced trees on hillsides, or as close
spaced gully plantings or shelter belts. Most
people are familiar with the narrow columnar
appearance of Lombardy Poplar, or the more
spreading crown of Frimley, both of which
were imported clones from Europe.
The arrival of
poplar rust in 1973, causing early leaf fall,
made them unsuitable for continued use. Hort
Research’s poplar breeding programme
based at Aokautere has been producing new
poplar clones that are better suited to New
Zealand climatic conditions. A major consideration
is the degree of resistance to poplar rusts
and leaf spot. Other useful characteristics
are such things as drought tolerance; improved
timber qualities (e.g. wood density); reduced
incidence of blackheart; low epicormic production
following pruning; and high leaf biomass production
for livestock fodder.
future drought proofing
are an ideal multi-purpose tree
providing soil conservation,
stock shade and shelter, fodder
in a drought and also timber.
of poplars in soil conservation is due to
the roots acting as a vast mechanical nchor,
along with the tree’s ability to draw
up water from the soil, reducing water pressure
in the soil pores and thereby lessening the
risk of large scale soil movement.
Poplars are an
ideal shade and shelter tree, with farmers
having survived droughts by cutting poplar
foliage for their livestock. A positive aspect
of this fodder is its ability to minimise
internal parasite burdens and boost reproduction
performance in livestock.
TIMBER PRODUCTION AND AGROFORESTRY
Poplar is a major
timber species in various countries. Two varieties
with timber potential are Kawa and Veronese,
which have been tested by Forest Research
for wood density as well as sawing, seasoning
and machining properties. Poplars are ideal
for large wet seepage areas in plantations
and farmland. They will dry out such areas,
suppressing rushes and allowing grass to grow.
When you decide
to plant poplars it is important to consider
what you want the trees for – conservation,
shelter, fodder or timber. Your end use will
determine the shape of the tree you need.
This information and the level of moisture
at the site will help determine the number
of trees and which clone you choose to use.
For soil conservation
they are ideally planted at 40-80 stems per
hectare depending on moisture availability,
wind exposure and ongoing management.
For shelter and
shade it is important to decide how large
a shelter belt you require and how you intend
to manage it. All poplars provide good shade
As fodder, the
summer pruning of poplars in a drought can
be extremely valuable.
poplar clone for your site?
Wind Eposed Sites
A willow block
is useful for absorbing effluent at peak times
when sumps and storage ponds are full, and
spraying on pasture may cause harmful runoff.
A study by Professor
Tom Barry, of Massey University, looked at
the effects of supplementing the feed of ewes
grazing drought pasture with willow and poplar
over the 10 weeks of late summer and autumn,
including the mating season. The ewes consumed
willow or poplar leaves and stems 3-5mm thick.
On average, over three seasons the improvement
in the reproductive rate was about 20%.
browse blocks on rush infected wet areas,
these largely unproductive areas have been
dried and volunteer pasture has grown under