[CH] Saving Seeds
Bob Batson (rcb@kc.rr.com)
Thu, 20 Mar 2003 20:16:17 -0600
Long-Term Frozen Storage
Seeds of all species can be stored for many years with almost no loss
of germination and only minimal loss of vigor, when dried to about 8%
seed moisture, sealed into an airtight container and frozen. Seeds
stored using these techniques will maintain their viability for up to
ten times longer than normal germination rates. Freezing does not hurt
seeds that have been dried to moisture levels of 8% or less. If the
seeds are not thoroughly dry, however, the excess moisture expands when
frozen and will rupture the cell walls. A quick and easy test is that
seeds will break instead of bending when folded, if their moisture
levels are 8% or less.
Color-indicating silica-gel is an excellent "desiccant" (moisture
absorbing material) for drying seeds. By comparison, powdered milk is
less than 10% as effective as a drying agent. Silica gel, which looks
like little plastic beads, is often treated with cobalt chloride which
indicates how much moisture has been absorbed. The beads are deep blue
when completely dry, but gradually change to light pink as moisture is
absorbed. Silica gel can be re-activated indefinitely by drying for
eight hours in a 200 degree Fahrenheit oven. Batches weighing over a
pound should be stirred occasionally to speed up the drying process.
Always dry silica gel slowly, because temperatures that are too high can
scorch and ruin it, turning the beads black.
Silica gel can also be dried in a microwave which works on the
moisture in the material. It only takes about 25 minutes to dry an 8- x
12-inch glass dish that is filled with silica gel to a depth of 1.5- to
2-inches. Progress can be checked by watching through the glass door of
the microwave as the silica gel changes from pink to deep blue.
Whichever drying method is used, the silica gel is then stored in an
airtight container to keep the material dry until it is needed.
The drying process requires a glass jar with an airtight lid, at least
half a pound (1/4 kilo) of good desiccant such as color-indicating
silica gel, and the seeds. Each sample of seeds should be placed in a
paper packet and carefully labeled. Determine the total weight of the
seeds and packets, and then measure out an equal weight of dark blue
silica gel. Place both the packets and silica gel into the jar and
screw the lid on tightly. The silica gel will immediately start
absorbing moisture from the seeds.
Both large and small seeds reach optimum moisture levels for storage
after seven or eight days in the container. Peas, beans and corns
usually contain 6-8% moisture at the end of that period, which is dry
enough to greatly increase their storage life while avoiding dormancy
problems that can occur when legumes are dried to under 5% moisture.
Small, soft seeds such as peppers and tomatoes will reach a lower 4-5%
moisture level during that period, because their mass is so small.
Small seeds aren't damaged if moisture levels remain above 3%.
After seven or eight days, open the jar and separate the packets of
seed from the silica gel. The seed packets are then stored in another
moisture-proof container without any silica gel in order to maintain the
low moisture content of the seeds. The second container could be
another glass jar or any similar moisture-proof container. Thoroughly
dry seeds reabsorb moisture quickly, so always try to minimize the time
the seed packets are exposed to the moisture in the air while being
shifted to the second container.
Another type of container proving to be really versatile is a flat bag
that has laminated walls made from layers of paper, plastic, foil and
another layer of plastic. Individual paper packets of dry seeds can be
be heat-sealed inside of these packages with a Microseal II(tm) or a
thermo-impulse heat sealer.
Paper/poly/foil/poly packages can even be sealed shut with an ordinary
clothes iron set on "wool" and applied to the open end of the bag for
three seconds. When the pouches are filled with water and sealed, a
person can stand on them without the seals leaking. If that person
jumps on them until the pouch breaks, the sealed edges are still
perfect. The sealed edge can be cut off with a pair of scissors,
seeds can be taken out and the pouch can be resealed. The outside of
the pouch can be written on, since that layer is paper, but for
safety's sake always put a label inside with the seeds as well.
Several small packets can be sealed into each laminated pouch. The
pouches can be stored directly in the freezer, take up very little
space, and are inexpensive.
The very best place to store an airtight container of THOROUGHLY dried
seeds is in a freezer. The next best place is in a refrigerator,
followed by any cool area where the temperature fluctuates as little as
possible. When retrieving seeds from frozen storage, ALWAYS allow the
sealed jar to reach room temperature before opening. Let the jar set out
overnight, whenever there is sufficient time. If the jar is opened
before the seeds reach room temperature, moisture will condense on the
cold seeds and rehydrate them. Also try to limit the number of times
seeds are retrieved from the jar, because temperature fluctuations
gradually reduce the viability of the seeds. When removing seeds from
storage that have been dried to low moisture levels, expose the seeds to
the air for a few days before planting, if time allows. This will let
the seeds slowly pick up some moisture, instead of going immediately
from low moisture to a very moist planting environment.
Excerpted from _Seed to Seed_ by Suzanne Ashworth (ISBN 0-9613977-7-2).
Reprinted with the permission of the publishers, The Seed Savers
Exchange (3076 North Winn Road, Decorah, Iowa 52101; tel. 319-382-5990,
FAX 319-382-5872).
--
Bob Batson
rcb@kc.rr.com
"Chocolate is the true opiate of the masses!"