Agriculture Reference
In-Depth Information
Fruitingwood
Old cultivars of walnut flower and produce
nuts at the tips of their branches. The male
catkins are borne on last season's wood, while
the females arise from the current season's
growth. In such trees no pruning is necessary
to promote this wood so keeping the tree
open to light and air will allow each nut to
have its place in the sun to develop fully (see
'Maintenance', below).
New cultivars that are the mainstay of the
Californian industry, bear nuts on the
tips of branches as well as on one-year-old
side growths. These will need thinning
regularly so that the canopy does not
become crowded.
Figure 6.37
This delicious nut can be self-fertile but the
best crops result from cross-pollination from another
cultivar.
The root system on such trees is tiny
compared to the aboveground parts and will
need to be brought into balance with some
pruning at planting (see pages 16 and 17,
'The root to shoot ratio'). Commercial
growers recommend cutting back the stem to
within five or six buds of the graft to balance
the above- and below-ground parts. In warm
regions where summer temperatures are
frequently above 30°C, such severity may be
detrimental. Retaining leafy side growths in
the trunk will protect the young bark from
sunburn, so consider your climate and prune
accordingly. A plant with such little anchorage
means staking is essential (see page 24,
'Staking'). The tree may take some time to
establish; however, once it has settled, prune
to encourage wide angled scaffold branches
that are spaced at least 60 cm apart. Side
growths from these can be thinned to 20 cm
apart. Once your framework has been
established, future pruning will depend on
what cultivar of walnut you have planted.
Maintenance
Walnuts are prone to fungal diseases and it is
important to keep the crown of the tree open
to air and light for disease prevention as well
as optimum crops. Again, depending on your
climate, reducing the canopy can lead to
sunburn of both the bark and the nuts. Know
your climate and prune accordingly.
Modern cultivars will need their laterals
thinned regularly to promote more side
growths and also to open the tree to light.
Such trees should also have at least one limb
removed each year once established.
Harvesting
The outer shell of the nuts will split and
the nut drop to the ground when harvest is
imminent. Knock a few more off the
branches and taste to see if they are ready. If
so, harvest them before the wildlife finds
them.