seeds

In response to the questions about planting and germinating iris seeds,
here's the section on the subject from the manuscript of my
book-in-progress.  Your comments and experiences would be very welcome.

IRISES FROM SEED
        Perhaps the most extensive seed list available is that of SIGNA,
the Species Iris Group of North America.  Literally hundreds of species and
varieties of every kind of iris (and a generous selection of iris
relatives) are offered annually to members at the bargain price of $0.50 a
packet.  You must be a member to recieve the list; see the next chapter
(Chapter 10) for information on how to join.  Commercial seed catalogs
usually list only a few iris varieties or species for sale (an exception is
Arrowhead Alpines [see Sources] with over 60), so producing your own seed
is one solution to the problem of how to obtain seeds--that will be the
subject of the next section.

  Iris seeds are large and easy to handle; most types provide no challenge
to even the beginning gardener. Like any seed, there are three basic
components: a tough outer seed coat,  enclosed stored food to nourish the
young seedling, called endosperm, and finally the young plant or embryo
itself.  In fresh seed, the coat is often taut and shiny, but as the seed
dries, the endosperm looses water and the seed coat wrinkles.  This is no
cause for alarm but is a natural process; the drying makes it possible for
the embryo to enter dormancy, a state of suspended animation that can keep
it alive for years if neccessary, until the proper conditions for
germination, or sprouting, occur.  Seeds of some types of iris, such as
Arils, can remain good (viable) for at least up to ten years; in other
types the seeds are not so long-lived.  Perhaps the record amongst seeds
for longevity is held by the 3000-year-old lotus seeds found in a Japanese
peat bog, which subsequently germinated and flowered.

 Seeds of different iris groups have a different look.  Bearded Irises have
rich brown seeds, which, when fresh, have a shiny seed coat.  Upon drying,
however, the seed coat becomes wrinkled as the endosperm looses water and
shrinks.  Long-lived Aril Iris seeds have a white or cream-colored knob,
the aril, on each seed.  This attracts insects, probably ants, which carry
the seeds far and wide.  The seeds of Louisiana Irises have an extra layer
of the seed coat that is thick and corky, so that the seeds float and can
be dispersed by moving water.  Iris prismatica, a North American native, is
called the Cube-seeded Iris, for the shape of its seeds.

 Seed ordered through the mail is, by definition, not fresh.  Iris seeds
arrive looking, for the most part, wrinkled and sere.  Included in any
packet may be a certain amount of chaff or of inviable seeds, which usually
can easily be told from the viable ones.  However, I always plant even the
smallest, most wrinkled-looking seed on the chance that it might, after
all, germinate and produce a world-beating plant!  These dried seeds have
entered a dormant state, induced by substances in the seed coat and
endosperm called germination inhibitors.  Inhibitors are commonly found in
the seeds of most perennial plants, and keep the seeds from germinating at
inappropriate times when the survival of the seedlings would be in
question.  Before the seed can germinate, the inhibitors must be washed out
or neutralized, which can best be done by a process known as
stratification.  This will occur naturally if you plant your seeds outdoors
in the garden in late fall.  Autumn rains and the water from melting snow
will leach the inhibitors from the seeds; the process is enhanced by cool
or cold temperatures (around 40 degrees F or below) for at least six weeks.


 Seeds may be planted in rows outdoors in a sunny protected spot.  The soil
should be prepared much as for a bed to be planted to iris rhizomes, and
tilled and raked until all clods have been broken and a fine, level surface
achieved.  Plant the seeds at least one inch apart, and at a depth three to
four times their diameter.  Deeper planting, up to an inch, is sometimes
recommended for very cold climates, where alternating freezes and thaws
might heave the seeds up close to the surface.  Seed rows should be
carefully marked.  Don't rely on your all-too-fallible memory to recall
where the seed rows are and what was planted there!  Seed beds can be
mulched for the winter with the lightest and airiest of materials, paying
special attention to the task of removing the mulch in spring; it must be
done carefully so that the seeds are not disturbed.

  I prefer not to trust the vagaries of weather and start my iris seeds
indoors.  This can be done in a greenhouse, sun room or even on a bright
windowsill.  The seeds are planted in November in a standard commercial
potting mix.  Such a mix has an advantage over soil you might get from your
garden: it has been sterilized and will contain no disease organisms.  If
you insist on using your own soil, consult your local extension agent on
means of sterilizing it.  I've had success microwaving small batches of
damp soil mix on high for about 10 minutes, but others who share your house
might object strenously both to the smell of cooking soil and the use of a
kitchen appliance for such a purpose!  Up to 20 iris seeds can be planted
in a 4-inch pot, provided you will transplant them before they become too
crowded.  The pots chosen must have drainage holes in the bottom.  For good
measure, the pots should be sterilized, too.  Wash plastic pots thoroughly
with soap and water, then rinse them with a solution of one part chlorine
bleach to nine parts of water and let them dry completely.  Plastic pots
are preferable because clay pots are riddled with microscopic pores in
which disease organisms can hide from the sterilization process.  If you
insist on using clay pots, they must be heat-sterilized.  After a thorough
washing, place the wet pots in a 350-degree oven for 30 minutes; the
sterlization process is enhanced if the pots are well-soaked.  Disposable
fiber-base flats do not have to be sterilized, but should be used only
once.  Wooden, reusable flats are not recommended because they are too
difficult to sterilize.

 Seed may be planted in pots just as you would plant it outdoors.  Be sure
the soil in each pot is thoroughly moistened, but there should be no
dripping from the drainage holes.  After carefully labelling the pots, each
is placed in a plastic bag and the bags are put into an old refrigerator
purchased for just this purpose, adjusted to between 35 and 40 degrees F.
Here they stay for six weeks, undergoing the process of stratification,
just as they might if they were planted outside.  Starting seedlings in
pots can help short-season gardneners in that the young plants can be
germinated weeks before garden-planted seed, giving the irises extra time
to make good plants their first summer.  But please remember that irises as
seedlings require the brightest possible light.  If a greenhouse is not
available, you may not want to try this method.  In dim light, the
seedlings will become weak and spindly and the whole purpose of an early
start is defeated.  A compromise method used successfully by many iris
enthusiasts is to plant the seeds in pots, but then put the pots outdoors.
They must not be allowed to freeze solid, however, and should be kept under
a pile of mulch or in a cold frame.

  When weather warms in spring, watch for the tiny green spears of the new
seedlings emerging above ground level.  Each small seedling will remain
linked to its seed (which stays underground) by an umbilicus-like structure
called a cotyledon.  This allows the plant to continue to withdraw food
from the endosperm and so grow rapidly to a self-supporting size.  Within a
few weeks, the seedlings will reach four to six inches in height.  At this
stage they will have exhausted the reserves in the seed, have good root
systems, and be living and growing on the food produced in their own
leaves.

 Potted seedlings, and to a lesser extent those grown in the ground, may be
attacked by a soil-borne fungus disease called damping-off.  This causes
the young seedlings to rot at soil level and fall over.  Damping-off can
run through a pot of seedlings at lightening speed.  Even though sterile
mix was used to pot up the seeds, airborne spores can infect the pots
afterwards.  Damping-off is almost a certainity if unsterilized garden soil
is used to pot up seeds.  At the earliest sign, drench the pot with a
systemic fungicide; this should handle the problem and stop the fungus in
its tracks.

 The young seedlings should be transplanted to a permanent position before
they become so crowded as to interfere with one another; the more robust
seedlings will crowd and inhibit their less rugged neighbors.  The nursery
bed for the seedlings' first year should again be prepared just as for a
planting of iris rhizomes, but with special attention to maintaining the
fine tilth of the soil.  Your young seedlings still have rather small root
systems that will be set back by transplanting.  Fine soil, without large
clods, will allow these roots to come in contact with soil moisture and not
find themselves in spaces between soil clods where they will be likely to
dry out.  Even though transplantation is a shock to the roots of seedlings,
it is not necessary to cut back the foliage as you would do while
transplanting mature irises; this would shock them even more and prolong
their recovery.  It is wise to do the transplanting on an overcast day, or
even a drizzly one.  On sunny days, the young plants will lose a great deal
of moisture from their leaves, moisture that the disturbed root system will
be hard-pressed to make up.  If circumstances mandate transplanting on a
sunny day, wait until evening, so the cool, humid night will intervene
before the next sunny day.

Spacing of the seedlings in the nursery bed will differ according to the
type of iris; for Tall Bearded Irises, the likely subject of your first
experiments with seed-growing, at least a foot apart is recommended.  Those
types that might take longer to reach blooming size, such as Louisianas,
Japanese Irises, or Siberian Irises, should be set out further apart,
perhaps as much as eighteen inches.  Properly cared for, the transplants
will grow rapidly.  Be particularly alert for foliage diseases (see Chapter
2) on bearded iris transplants, as they can slow growth considerably by
robbing the plants of leaf surface with which to make food.  By the time
the new plants' first autumn comes, they should be robust and on a par with
freshly divided, established plants.  The decision as to whether to provide
some form of winter protection is yours--follow whatever practice you use
for other iris plants of the same type.

 Bearded Iris seedlings that have been well-treated will often bloom the
next spring after germination.  By late summer, those seedlings that are
preparing to bloom the following spring will usually show two or more
smaller leaf fans on either side of the main fan; these increases will be
the blooming rhizomes of two years hence.  For other iris types, the wait
for bloom may be longer.  Most beardless types will need another summer's
growth, though a few scattered blooms may occur.  Aril Irises and bulbous
sorts often require extra time; in particular the bulbous irises may not
bloom for as much as five years.  When the foliage of bulbous seedlings
dies down, the bulbs may have to be lifted and stored in a warm place to
provide the required period of summer dormancy.  This can be difficult
because the first season bulbs are very small, pea-sized at the largest.
Search for them carefully when digging!

 If you enjoyed the experience of a morning walk in your garden at iris
time, revelling in the new blooms of the varieties purchased the previous
year, you'll find the excitement at a whole new level when the new flowers
are produced by your seedlings.  Even that pales to nothingness when the
seedlings that are blooming are from hand crosses you made and planned
yourself.  This is truly creative gardening--not just planning and
designing using known plants, but an exploration of the unknown, creating
plants that have never before existed and that are unique in all the world
to your very own garden.

Best wishes, Bill
___________________
William A. Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943 USA
phone (804) 223-6172
FAX (804) 223-6374
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index