Saving, Storing and of course Planting Seeds Part 2
james...@gmail.com
By James Cerwin
PART # 2
Basic Isolation Practices
Plants which can be cross-pollinated by similar varieties are easy to
save if only one variety of
The same species is grown at a time (e.g., one eggplant or one carrot).
If you want to grow more
Than one crossable variety of a species at a time and save genetically
pure seed from any of
Them, however, you can still prevent crossing by 'isolating' the
plants. The simplest way to
Isolate varieties is by planting them far enough away from each other
so that cross-pollination
Is not possible (see Distance Isolation). The amount of space needed
for safe distance isolation
Varies for different plants-and there is always the risk that someone
nearby may grow a
Cross-pollinating variety, so get to know your gardening neighbors!
If space is not available, isolation can be achieved in other ways. One
way is to grow each
Variety in separate screened cages (see Caging), or to cover individual
flowers with bags (see
Bagging and Hand Pollination). In another method, called "time
isolation," growers time plantings
So that different varieties are not flowering at the same time, and so
cannot pollinate each
Other (see Time Isolation).
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Distance Isolation
Some plants can be protected from cross-pollination by separation by
only a small distance, such
As lettuces (25 feet of separation) and eggplants (50 feet). Other
plants, such as peppers,
Stretch the possibility of distance-isolation in the average garden by
requiring 500 feet for
Safe isolation between varieties. Insect-pollinated plants such as the
cabbage family (collards,
Broccoli, etc.), squashes and okra require from ¼ to 1 mile for
complete safety-often difficult
To accomplish or verify, due to gardening neighbors. Corn, a
wind-pollinated plant, can require a
Mile or more for safe distance isolation and members of the Beet Family
may need as many as 5
Miles!
The exact distance you'll need for safely isolating a particular crop
depends on a number of
Factors. Central among these factors are the type of plant and how it
is pollinated (i.e., wind,
Insects, self-or a combination of these). Also important are the
particulars of your growing
Situation including location, climate, prevailing wind patterns and
surrounding terrain and
Vegetation features.
Relative size of plantings can have an impact, too. Small plantings are
more vulnerable to
Foreign pollen than large plantings, since in a large planting foreign
pollen is spread among
More plants. Further, plants on the edge of a group are more vulnerable
to crossing than plants
In the middle. For this reason, whenever a variety is important,
collect seed from plants nearest
The center of a planting for greatest purity.
These and many other factors help account for differences between the
distance-isolation figures
Given by Suzanne Ashworth in Seed to Seed and those given by the USDA
or other authorities (see
The Plant Isolation Distances Table). While the USDA figures are based
on large plantings, Ms.
Ashworth's figures are better-adapted to the scale of the home
gardener. Actual distances which
Will work for you may have to be determined experimentally... until you
know that smaller
Distances are safe for your conditions and plant varieties, use the
larger distances. Caution is
Especially important with rare or heirloom plants. If you experiment
with smaller isolation
Distances, use common varieties instead of rare ones in case of
accidental cross-pollination.
Remember that once two varieties have crossed, their genes are
inextricably crossed.
Wind Pollination and Distance Isolation
Distance needed for distance isolation of wind-pollinated plants
varies. Wind patterns and
Strength, existence of windbreaks, etc., all have an effect.
Wind-pollinated plants grown in
Wooded, low-wind areas will need much less distance than the same
plants grown in vast, open,
Windy areas, for instance. Pollen from corn, which is relatively heavy,
falls to the ground
Within a few paces in a quiet protected spot, but can travel half a
mile or more in open, windy
Areas. Windbreaks are more effective for plants with heavy pollen like
corn, than for plants with
Light pollen like beets or lamb's quarters.
Insect Pollination and Distance Isolation
Isolation distance needed by insect-pollinated plants varies according
to what animal or insect
Is the pollinator, and on how plentiful local nectar and pollen sources
are. In areas where
Nectar and pollen sources are plentiful, bees and other pollinators do
not have to travel as far
In their foraging as in sparsely-vegetated areas. If bees are the
pollinators, distances needed
Also depend on which hives collect from where within your local area.
Bee hives are territorial
And do not overlap foraging areas-plants in one hive's territory
won't be bee-pollinated by
Plants in a neighboring hive's territory. For this reason, distances
needed to isolate
Bee-pollinated plants in areas with plentiful, diverse vegetation may
be a quarter-mile or less,
Whereas distances for the same plants in sparsely-vegetated areas might
be a mile or more.
Self Pollination and Distance Isolation
Self-pollinated garden plants' flowers include both male and female
parts and are receptive to
Their own pollen. This allows them to fertilize themselves. Among
self-pollinating plants, some
Are exclusively self-pollinated, whereas others can be fertilized
either by themselves or by
Other plants of the same species.
Self-pollinating plants whose flowers are open during the time
pollination takes place (such as
Okra or peppers) can either fertilize themselves or be pollinated by
other plants.
Self-pollinating plants which fertilize themselves before their flowers
open (such as tomatoes
And beans) are exclusively self-pollinating. These latter do not need
to be isolated, since by
The time their flowers open they will have already pollinated
themselves.
Even plants whose flowers are closed during pollination, however, might
cross-pollinate under
Certain circumstances. Self-pollinating flowers can be forced open by
hungry insects in areas
With few nectar or pollen sources, for instance. For these reasons even
plants which do not
Normally cross-pollinate may need protection from nearby varieties of
the same species in deserts
Or other sparsely-vegetated regions, or if their purity is extremely
important.
Time Isolation
When distance isolation is a problem, caging is too costly or
troublesome, and you're only
Growing a couple varieties in a season, use time isolation to prevent
crossing. Time isolation
Works with any two varieties that shed pollen over a limited time and
have sufficiently different
Rates of maturation (as usual, don't forget your gardening neighbors,
who may be growing
Varieties that will cross with yours).
To use time isolation, planting dates of two similar varieties are
staggered so that by the time
The later of the two varieties is flowering, the earlier variety has
already finished flowering
And is no longer producing or receptive to pollen. Plant the earlier,
faster-maturing crop a
Couple or three weeks before the later, slower-maturing one. If they
are plants which flower over
A short time, the two flowering periods may not overlap at all. Even if
the flowering periods of
Two crossable varieties overlap a little, time isolation may still be
an option. The secret in
This case is to manually prevent flowers from blooming on both
varieties at once. Simply remove
Late flowers from the earlier-flowering variety (after seeds have been
produced) so that the
Later crop can pollinate and set seed without being crossed. Remove
flower buds well before them
Open, since some varieties open early in the morning. This method can
work well with plants which
Produce seed over a long season, such as okra.
Caging
If safe isolation distances are not available and time isolation is not
suited to the plant (as
For basil with its long flowering period), 'caging' or 'bagging'
techniques can be used to insure
Against crossing. In caging, plants are protected by cages covered with
mesh or fabric. The weave
Of the covering must be small enough to prevent passage of insects or
pollen (depending on
Whether the plant is insect or wind-pollinated, respectively). Bags
over individual flowers or
Flower heads can be used for self or wind-pollinating plants. In this
case the bags simply act as
Tiny 'cages'.
Insect Pollination and Caging
Cages covered with regular window screen are fine for keeping insects
safely away from
Insect-pollinated plants. Use large frames which hold the mesh away
from the plants inside them,
So that insects cannot reach flowers that might otherwise press against
the inside of
Close-fitting cages. Build the cages large enough for the plants at
maturity, and place them over
The plants as soon as they start to flower (remove any flowers which
open before the cages are
Put into place).
Caging procedures vary according to whether your plants can
self-pollinate (such as peppers), or
Whether they are insect-dependent and so actually require insects for
pollination (such as squash
Or basil).
Alternate-Day Caging
Insect-dependent plants-which actually require insects for
pollination-must have their cages
Removed periodically so that insects can reach their flowers and
pollinate them. Plant two or
Three varieties and cover them with separate lightweight cages. Once
every other day (for two
Varieties) or every three days (for three varieties) in rotation,
remove a cage from a different
Variety. Don't remove cages from any two varieties on the same day, and
replace the removed cage
In the evening. This exposes a different variety to pollinating insects
each day, and gives each
Variety a chance to be pollinated every two or three days. Remember,
however, that even removing
Just one cage at a time can still allow crossing if your neighbors are
growing plants that will
Cross yours.
Insect-pollinated plants which are also self-pollinating can be left in
their cages full time and
Will produce seed.
Wind Pollination and Caging
When using cages to protect wind-pollinated plants from crossing, cover
the cages with fine-weave
Fabrics (such as spun polyester) that keep pollen out but allow air and
sunlight to pass. Grow as
Many plants as possible inside each cage for a large genetic base.
Shake plants or cages daily to
Help distribute pollen inside the cages. If the plants you're
protecting are small and
Closely-planted, spun polyester or like material can simply be wrapped
around the group and tied
At the base to form a frameless 'cage'. Be sure to thoroughly seal the
bottom of the bag with
Cotton, leaves or mulch, etc.
Bagging and Hand Pollination
If none of the above isolation techniques are practical for you, or you
want to maintain a high
Degree of control over which plants pollinate each other, you can
individually hand pollinate
Flowers or flower heads and enclose them in cloth or paper bags. This
technique works well with
Large-flowered plants such as squash or daylilies.
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