Planting Walnut Trees From Seed

Walnut seeds won’t germinate immediately when planted because they
are in a dormant state, and you must break their dormancy before the
seed can germinate.  Both scarification and stratification are
required to break a walnut seed’s dormant state, for germination to
occur.

The black walnut’s dormancy is caused by the thick, hard seed coat.
Breaking or weakening the seed coat is referred to as scarification,
and is the first step necessary to break the seed’s dormancy.  A
metal file or coarse sandpaper can be used, but is difficult and
time consuming, unless you have a power sander.

Treatment with boiling water also works.  Place seeds in water of
170 to 210 degrees F.  Make sure it’s not boiling!   After the water
cools, continue to soak seeds for 12 to 24 hours. The process
is slow, because you need to use 10-20 times the volume of hot water
as seed.

Whatever scarification method you use, you must be careful not to
damage the embryo inside. Once scarified, seeds will not store well
and should be planted as soon as possible after treatment.

If scarification is done naturally after planting the seed coat may
be broken by microbial action, exposure to alternate freezing and
thawing, or fire. Depending on nature to scarify your seeds may
require leaving them in the ground longer than one year.

The second step in breaking the black walnut seed’s dormancy is
stratification. This requires being exposed to cool temperatures
and moist conditions for several months. Winter weather in the
Northern USA provides the necessary conditions to break dormancy
naturally.

You can also break the seed’s dormancy by stratification in a
refrigerator. Using a coffee can, plastic jar, cottage cheese
container, or a plastic bag, place the seed in a moist 50:50 mixture
of sand and peat-moss. Punch holes in the lid of the container to
provide air.

Let’s take the process from the start: Collect your walnuts
immediately after they fall to the ground – before the squirrels get
them. Remove the husks, then place the nuts in water. Nuts that
float are not viable and should be discarded. The viable nuts will
sink to the bottom.

Scarify your nuts, and plant 1 to 2″ deep in the fall or stratify
the nuts in a refrigerator at 34 to 41°F for 90 to 120 days and
plant in the spring.  Use the natural soil, or Grow-Boxes that are
open to the soil beneath the box, because walnuts produce a long
taproot.

Prepare the soil with Pre-Plant and Weekly Feed, then after the
seedlings emerge feed 3 times each year.  Walnut seedlings grow
fast, and it’s recommended they be transplanted into the orchard
within 2 years after germination, unless you have tree-planting
equipment.

Jim Kennard