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Propagation Series Part 3: Seed Germination, Part 1

            	PROPAGATION SERIES PART 3:  SEED GERMINATION, PART 1
                                 (By Amber Hearn)

Surprisingly, although most gardeners think nothing of raising vegetables
from seed in the garden, or sowing a row of Marigolds or Zinnias, many of us
do not even consider growing hardy plants or some of the other annuals, such
as Petunias from seed.  Many of these plants, however, are as easy to grow
from seed as any of the ones commonly grown. 
  
                                VEGETATIVE V. SEED
 
One of the main things to keep in mind when deciding to start seed of a
particular plant is the end goal.  There are two basic types of propagating.
Vegetative and Seeds.  Vegetative propagation is further broken down into
different techniques such as divisions, cuttings, layering and cell culture.
When propagating a plant we must first decide what method we should use to
give the desired results.  Vegetative propagation is a good choice if we
desire plants that are identical to the parent as all vegetatively
propagated plants are clones of their parents.  If you desire more plants of
a  vegetatively propagated hybrid, the only true way to get them is by 
vegetative propagation.     

Sowing seeds on the other hand will produce progeny that may or may not be
similar to the parent plant, especially if that plant is a vegetatively
propagated hybrid or cultivar.  Plants are often cross-pollinated with other
plants by insects or wind. This is of course mother-natures way of ensuring
the diversity and health of any given species.  This variation may be only
slight and to all intents and purposes they may be identical to the parents,
but it is still the progeny of two different plants and cannot be said to be
the same plant, any more than children are the same as their parents. 

Once, when I was talking to someone about starting Hosta seeds, I told them
that they shouldn't expect to get seedlings identical to the parent plants.
I evidently wasn't very clear, because this poor confused person then asked
me "Well if I won't get Hostas from the seed, what will I get?"  So to
clarify this, if the plant is a Hosta, all of the seedlings will still be
Hostas, they just may not look identical to their parents.  If you examine
any species of plant in it's natural habitat, you will see a great deal of
diversity, whether in flower color, or size, leaf shape, height of  plant,
etc. At first this variability may seem undesirable in the garden where you
want more control of your plants, but if  you are like me,  you may rejoice
in the diversity seed grown plants offer.  If in the end, you are selective
about keeping only the seed grown plants that demonstrate the properties you
are looking for, you may end up with a good seed grown strain, or even
better a great hybrid, good enough to market.  At the least, you will end up
with a garden full of wonderful healthy plants. 

If you are propagating a true species, seeds often provide longer lived,
sturdier plants than those grown vegetatively.   The reason for this is
twofold.  If the plant that is used for vegetative propagation is diseased,
this disease is transferred to the new plants.  Many of the common diseases
that affect garden plants are not, however, transferred to the seed.
Secondly, the older a cultivar is, the harder it is to propagate, and the
less vigorous the resulting plants will be.  For example, if you propagate
vegetatively from a plant that is seed grown, the progeny will probably be
equally healthy and vigorous.  Say you market the resulting plants.  The
plant is then propagated by the buyers.  The resulting plants are slightly
less vigorous than the originals.  This downhill effect continues, until the
results are weak and sickly, or won't propagate vegetatively at all.   This
is not always true, but it is something to keep in mind.

That said, you may also want to keep in mind that vegetative propagation
will usually produce mature plants faster than seed.  The Trillium for
example can take over 7 years to flower from seed, but rhizome cuttings will
produce a flowering plant in 2-3 years.  

In addition, there are many plants that simply cannot be propagated through
the vegetative means available to the home gardener.   Your only other
option, in these cases, is to either buy new plants to replace old ones, or
grow them yourself from seed.  It is hard to replace a plant if you can't
find it available anymore. 

Experience will teach you better than any book or lecture which method is
best and the only way to get that is to experiment yourself.
  
                             BIOLOGY 101  

The Birth of a Seed:  It is not absolutely necessary to know a little bit
about the biology of seed to be able to grow plants from them.  Any of us
can throw seeds in the garden, or in a pot, and have fairly successful
results without any in depth knowledge of the seeds inner workings, but a
little basic knowledge never hurts.  So, at the risk of boring you to tears,
we're going to start with a seed biology refresher course.

Although not all plants produce seed (ferns, mosses, liverworts, lichens and
fungii do not), seed producing plants are the most complex and numerous
forms of plants on the earth today.   The seed producing plants are divided
into two classifications.  

	Gymnosperms: (jim nuh spuhrmz) These include evergreens (conifers) like
    your Christmas tree and their relatives. The plants in this class produce
    cones, which hold and release their seed.  

	Angiosperms: (an jee uh spuhrmz)The more numerous of the two classes,
    includes all of the flowering plants, trees and shrubs in the world. In
    Angiosperms, the flower is the reproductive structure.  It contains the
    reproductive organs that produce the seed. A flower may have either male or
    female organs, or both. Flowers with both are called perfect (tomatoes
    produce perfect flowers).  Flowers with either one or the other are deemed
    imperfect Hollies (Ilex species) produce imperfect flowers with male plants
    and female plants.  Which is why you must have both to get those beautiful
    red berries.  

In flowering plants, once the female parts ( I won't bore you with the
scientific names) are fertilized (pollinated) by the male sperm (pollen), a
seed or seeds are formed.  This usually takes place in the ovary of the
female.  The ovary then enlarges, and becomes the fruit of the plant.  The
fruit may be as complex as a peach, or as simple as a seed pod. 

This fruit is important in more than one way. First, it protects the seeds
from damage until they are dispersed.  Second, the makeup of the fruit often
aids in dispersal of the seed.  To be successful, a seed must germinate at a
distance from the parent plant.  The fruits are often designed to aid in
this.  Some taste good, are eaten, and the seeds passed at a distance from
the plant.  Some, like the Cocklebur, have protrusions which stick to the
fur of animals.  Some bear wings, such as the Maple fruit, to help the wind
blow the seed away from the parent.  And some, like the Touch-me-not, an
Impatiens species, explode when the seed is ripe, scattering the seed for
great distances. 

Of most interest to us as we study seed starting, is the third function of
the fruit.  The fruit of many of the plants that produce seeds encased in
fleshy fruit (Apples, peaches, grapes, walnuts, almonds, tomatoes etc.) also
contains a germination inhibiting mechanism.  This is usually a chemical,
contained in the flesh of the fruit, that keeps the seed(s) inside from
germinating before the appropriate time. This chemical is destroyed as the
fruit rots, or is passed through an animals intestine.  In seed starting, it
is sometimes necessary for us to remove this germination inhibitor
artificially. We'll talk more about that later. 

The Structure of a Seed:  The hard outer portion of the seed is known as the
seed coat.  The inside of the seed  is called the embryo. The embryo
consists of some basic structures.  These are the hypocotyl (hy puh kaht
uhl), which will eventually become the shoot or stem; the radicle (rad ih
kuhl), which is the basis for the root of the plant, and the epicotyl
(ep uh kaht uhl), the first true leaves. The seed also (usually) contains 
cotyledons (kaht uh lee duhnz).  The cotyledons are the are the seed leaves. 
The first one or two little leaves that appear on a seedling. They are not
true leaves, but are actually food storage organs.  A new seedling is not 
capable of producing it's own food.  Food is stored in the cotyledons for 
the new plant to use until it is capable of photosynthesis.   

The seeds of some plants produce two cotyledons these are named
dicotyledonous (dy kaht uh lee duhn uhs), but are called dicots (dy kahts)
for short.  Tomatoes and beans are dicots.  Other plants produce seeds which
have only one cotyledon.  These are named monocotyledonous (mahn uh kaht uh
lee duhn uhs) or monocots (mahn uh kahts).  Corn, and most grasses, are
monocots.  Monocot seedlings also contain endosperm, which is another source
of food for the seedling.  This is not a complete explanation, as it gets
more complicated than that , but for our purposes in starting seeds, all we
need is the basic knowledge that a radicle is the root, etc. 

Dormancy?:  After a seed is fully formed, it enters a period of inactivity,
or dormancy.  This dormant period is necessary before development into a
plant can continue.  If a seed did not go dormant after formation, it would
germinate in the fruit or seed capsule right on the plant.  This dormancy is
caused by germination inhibitors.  Usually (95% of the time) germination
inhibitors are chemical in nature, but occasionally they are physical (such
as seed coats that are impervious to water).  During dormancy, the
germination inhibitors are broken down, either chemically, or physically, or
occasionally both.  To be technically correct then, the seed is not actually
dormant, or inactive, it is undergoing changes that break down the
mechanisms that keep it from germinating.  Since the word "Dormancy" is such
an inaccurate term, I'm going to borrow a term from Norman C. Deno, a
groundbreaking organic chemist who has dedicated his retirement to
researching germination inhibitor mechanisms, and call this period
"Conditioning".  Conditioning occurs naturally, over a period of time in
nature, given the proper conditions.

The amount of time, or the forces required to condition the seed vary with
each species of plant.  The trick to getting a seed to germinate then, is
conditioning it so that it is ready to germinate.  

I'll talk more about seed conditioning in the next part of this lecture.
For now, I would like to give credit and thanks to Mr. Norman C. Deno for
his invaluable work on seed germination.  His published work, "Seed
Germination, Theory and Practice" has become a bible to me, and many other
propagators of plant seed.  Much of what I'm going to try to teach you is
derived from this work.  If you are interested in owning your own copy, send
$25.00 to:

 Norman C. Deno, 
 139 Lenor Drive, 
 State College, PA 16801.  

He explains germination inhibitors in detail, but more importantly from our
viewpoint, he specifically details the appropriate methods for conditioning
and germinating difficult seeds of over 4000 species.  This year, he
published a supplement to this, adding many more species to the list. It is
also available for an additional $15.00. These studies, are published and
distributed by Mr. Deno himself.  Treat yourself for Christmas, if you are
interested in starting seeds, it's the best investment you can make.  (No -
I did not get paid for this advertisement.)  

Are there any questions?



Sincerely,  

------------------------------------ FROM: -----------------------------------
Duncan McAlpine
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