Many seeds have ways to protect them selves from germinating at
the wrong time of the year. They have developed what is called dormancy. When the seeds environment is not suitable for
germination, namely lacking moisture, oxygen, or it's to cold; the seed is in a
quiescent state. Many seeds dispersed in the fall are not dormant but are
quiescent because they lack water or the right temperature for growth, if they
were provided water and a suitable temperature they would sprout. Quiescent
seeds are not dormant.
that the seeds are alive but they need something more than just water and optimal temperature before
they will start to grow.
Most vegetable and annual flower seeds have been selected over many generations
to eliminate dormancy and all they need is water and consistent temperatures
in the 60-80F degree range and they will germinate. But many perennial
species seeds have dormancy conditions that need to be met before they will
Dormancy is caused generally by three different mechanisms:
1) Chemical inhibitors that prevent growth.
2) Physical barriers that prevent the uptake or the movement of: water,
gases or chemicals with in the seed.
3) the embryo of the seed is not full developed and needs time after dispersal
Some seeds can have both chemical inhibitors and physical barriers plus have
undeveloped embryos or more than one type of each.
First we will deal with chemical inhibitors that prevent seeds from
Plants that have developed dormancy in their seeds have done so for a number
of reasons including challenges do to the environment they live in. Plants
that come from areas that have long cold winters for the most part
have some type of dormancy - once these seeds ripen in summer or fall there
is not enough time for the seeds to germinate and the seedlings to grow large
enough to over winter so dormancy prevents the seeds from germinating until
spring. The means to accomplish this are chemicals with in the seed
that prevent germination, these chemicals are destroyed by cold,
after the cold has dispelled the chemicals, the seed is able to germinate
and grow. Those plants that grow in dry regions of the world or were there
are dry periods seasonally, their seeds many times have dormancy requirements.
Once the seed has come into contact with enough water to wash away the chemical
compounds that retard germination they can begin to grow.
The process of coarse is much more complicated than the above lines
would indicate- there are both chemicals with in the seeds that prevent germination
and those with in the seed that promote germination and they work in tandem
with each other. Dormancy can be both primary in which the seeds do
not germinate right away after ripping (the seeds need to dry to a certain
moister content) and secondary dormancy - in which as time passes
seeds develop dormancy of which "deep dormancy" or " after dormancy" is one
factor. An example of dormancy developing over time would be the Delphiniums
or Monkshoods (Aconitum), fresh seed will germinate in one to three weeks
while seed that has been dried and stored needs a cold moist period to beak
down dormancy induced by chemicals with in the seeds.
The actual process of seed germination will be covered by a different page,
at hand we are concerned with how to germinate our seeds and raise our seedlings
into nice garden plants.