University of Vermont Extension
Department of Plant and Soil Science
Fall
News
Article
NUT TREES FOR
NORTHERN LANDSCAPES
Dr. Leonard Perry, Extension
Professor
University of Vermont
Along
with pumpkins and gourds, you often find a selection of nuts in stores
and farm
markets in the fall. If you like nuts
such as black walnuts, butternuts, Chinese chestnuts, and hazelnuts,
consider
growing your own as their trees are hardy in northern regions.
They make great ornamental shade trees as
well. Nuts are a good source of proteins
and other nutrients, feed wildlife, and require very few inputs of time
and
resources—much less than most fruit trees.
Although
most nut trees eventually can 50 feet tall or more, hazelnuts only grow
to
about 15 feet or so. You don’t have to
wait until trees are mature for harvest, as most start bearing in only
4 to 5
years from planting small trees. When
mature, most may yield 60 to 75 pounds of nuts, with 20 to 25 pounds
for
hazelnuts. Breeding over recent decades
has resulted in some nut cultivars (cultivated varieties) that are
hardier,
bear earlier and with more nuts, and may be more tasty and easier to
crack.
If
you’re sowing from seeds, fall is a good time, just as the
squirrels do. Make sure and cover with some screen or
netting so squirrels and chipmunks don’t find them. This
marks where they are too, as they may
not sprout until the following summer. Or you can sprinkle moth balls
or a
commercial repellent around them. Buying
small trees will get you a crop sooner.
If you’re
transplanting trees, spring is the best time and only for small trees,
as they quickly
develop deep tap roots making them hard to relocate.
Most
nut trees need at least two different cultivars, or just different
plants if
only a
species, but they
need to be of the same species. Often
wild species, if nearby, will pollinate a cultivar. Plants should
be within a hundred feet so the
wind can blow the pollen between plants.
Choose
a site with a deep (for the deep tap roots), well-drained soil.
Nut trees generally will tolerate a range of
soil acidity or pH. If growing from
seeds, the first year seedling gets its nutrients from the seed, so
there is no
need to fertilize. For small plants, or
second year seedlings, fertilize in spring with a fertilizer rich in
nitrogen. Keep trees well-watered, as
you would other trees, watering deeply once a week if no rain (more
often on
sandy soils).
Mulching around the trunk, but not up against
it, will help control weeds and prevent mechanical damage to the
trunk. Place a tree guard around trunks of young
trees to protect them from winter sunscald and mouse damage.
Stake trees for a couple years if they are in
a windy location. Raking leaves in the
fall will help prevent diseases, although nut trees seldom get any.
Choose
a site, too, with enough space for the tree to reach its mature size
without
interfering with buildings or other plants to the sides, utilities
below
ground, or overhead wires above them.
Don’t plant where shade will interfere with desired gardens,
flower
beds, or lawns.
Be
aware that black walnut and butternut give off a toxic substance
(juglone) to
many other plants, preventing them from growing nearby. This is
called “allelopathy”, and was first
noted on black walnuts by Pliny the Elder, a Roman natural science
expert of
the time, about 77 A.D. Lawn grass, some
annual flowers such as impatiens, and many herbaceous perennials are
not
affected by these trees, except perhaps by their shade.
Nut
trees need little pruning, except to remove broken or diseased
branches, or
ones too low that interfere with mowing or other activities. Too
much pruning actually can delay
fruiting. You can prune to keep to a
lower height, just make sure to keep a strong central trunk or
“leader” in
early years of small trees. As the tree
grows, remove branches that aren’t evenly spaced around the tree,
and that
aren’t about 18 inches apart from the others, measured
vertically. Also remove branches that are very upright,
as those at wider angles from the trunk will be stronger as they grow
and less
likely to break in storms or winter. Hazelnuts are an exception,
being pruned more
like a large shrub, with 5 to 7 main shoots. Prune out weaker ones, and
ones in
the center to allow light to enter.
You
can rake up ripe nuts as they fall, or shake small trees or branches of
larger
ones so they drop the ripe nuts onto a tarp spread below. If
picking nuts, you may get ones unripe,
which are very difficult to open. Don’t
allow nuts to remain on the ground, as they’ll decline and
rot. Lay them in a single layer on screens, or
similar, to dry in a warm area with good air circulation such as attic
or
greenhouse benches,. Periodically turn
the nuts. You can then store them in
burlap bags or boxes, or shell and freeze.
Frozen, the nuts will store for several years.
The
black walnut eventually reaches 50 to 75 feet high, and 35 to 50 feet
wide. It shouldn’t be confused with the
European or Persian walnut, the ones we usually find in stores.
In addition to the drawback of this native
tree of allelopathy, its nuts have a smoky and strong flavor that not
all
like. This tree has been used more for its
timber than fruit.
Butternuts
were a staple food of the Iroquois native peoples during northern
winters. This native tree is closely related to the
black walnut, reaching a similar size, but with flavorful nuts.
Pour boiling water over them, let stand 15
minutes, then tap with a hammer to crack open.
Unfortunately,
butternut blooms may be damaged by late spring frosts, and a disease
has nearly
eliminated them from natural stands in some areas.
The
hazelnut may be called an American filbert, as it is related to the
European
filbert which is slightly less hardy. It
has prickly burrs on the outside husk covering the nuts, making them a
bit
harder to handle. Recent cultivars may
have better fruit, and resistance to a blight disease. Growing
about 15 feet high and wide, it is
good for smaller landscapes.
The Chinese chestnut is the one
usually found for sale, as the chestnut blight of the early
1900’s wiped out
most our native American ones (although there are some resistant
cultivars you
may now find). It is often grown merely
as an ornamental, with its long leaves and sweetly fragrant
flowers. It is a bit smaller than other nut trees,
only reaching 40 to 60 feet high and 30 to 40 feet wide. Some
nuts can be eaten raw, but are usually
roasted over a fire or heated in a microwave for about a minute.
Look for cultivars with some blight
resistance.
There
are other nut trees that will grow in warmer areas (USDA zones 5 and
warmer),
including filberts, hickories, pecans, and walnuts. Almonds and
pine nuts usually are grown in
hotter or drier areas of the west. If
you want to learn much more about growing nuts, you may want to look
into the
North Nut Growers Association (www.nutgrowing.org).
There also is an excellent publication
available online or to order from Cornell University on Nut Growing in
the
Northeast (www.gardening.cornell.edu/fruit/pdfs/nutpub.pdf).
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