geophyte seed germination
giorgio pozzi (Fri, 12 Jun 2009 00:55:35 PDT)

SORRY but the attachment was lost

IAS Newsletter, 22: 1, 6-7.
Growing Arisaemas from Seed Jim McClements
Arisaemas are easy to grow from seed. The simplest way is to plant
the seeds in a pot of
Promix , or similar mix, put the pot outdoors, and let nature take
its course. Or, you can
plant the seeds directly into a bed. However, this often means a four
year wait for a
flowering plant, and also means that you won't have anything to keep
you occupied in the
winter!
Unlike many genera, Arisaema seeds do not require a cold period for
germination, and the
plants can easily be manipulated into a growing "year" of only 8 or 9
months. This allows
for a considerable shortening of the time from seed to flowering, if
one wishes to get into
the process of growing under lights and has refrigerator space
adequate for "artificial
wintering". Over the past five years, I've evolved a system for this
which I hope some will
find useful.
When arisaema seeds are removed from the ripe berries, they are
covered with something
that inhibits germination. Under natural outdoor conditions, this
inhibitor is washed away
from the seed, usually over the winter, and germination can occur
when warm weather
returns. However, it's also possible to remove the inhibitor
artificially. Soaking for a week,
with daily changes of water, works, and some have even gone so far as
to recommend
suspending the seeds in a mesh bag in a toilet tank, where the water
is changed frequently.
However, the simplest method, devised a few years ago by Ray
Stilwell, is to put the seeds
into a glass of water with a drop or two of detergent (I use "Dawn"),
soak for 1-2 hours,
and then rinse thoroughly (I use a strainer).
The next step is to put the seeds in a thrice-folded, damp (not wet),
paper towel (white,
no dye) which is then placed in a polyethylene food storage bag,
closed by folding. (This is
the method for seed germination originated by Marjorie Edgren and
popularized by
Norman Deno.) Several folded towels can be placed in one bag, which
is then kept in a
warm place and checked once or twice weekly. As soon as one or two
seeds show a
radicle, it's time to move to the next phase. I give the seeds as
long as three months to
germinate, but most will do so within a few weeks. Infertile seeds
will rot quickly, and I
am convinced that rotting is primarily due to non-viable seeds, not
fungal contamination. I
tried prophylactic fungicides for a while, but have stopped, fearing
that they might be
causing more harm than good.
When a few seeds in the towel germinate, I plant them all. I have
been using pure Turface
(calcined clay) as a medium. The germinated seeds are placed into
small holes in the
wetted Turface, and the pot is placed in an inch of standing water
with a small amount of
standard houseplant fertilizer added (Schultz Plant Food, 20-30-20).
Don't try this with
potting soil. Plants will rot. But Turface allows enough oxygen
throughout for the
seedlings to develop normally. The pots are kept in standing water,
in flats, under lights in
my basement.
In a few weeks leaves appear, and the seedlings grow on for several
months. When they
turn brown and wither, it's very easy to separate the small tubers
from the Turface. They
are then placed in a food storage bag with some slightly moist
Turface, and refrigerated
for about three months. (The Turface from the pots can be rinsed and
recycled.)
After three months of cold treatment, the bag containing the tubers
and Turface is placed
at room temperature. If the Turface is dry, a small amount of water
is added. The bags are
checked once or twice weekly and as soon as a sprout begins to
elongate, the tubers are
ready to be replanted. Occasionally the tubers will have started to
break dormancy while
still in the refrigerator, and can be planted immediately.
Tubers in the second growth cycle do NOT do well in the wet Turface,
but tend to rot. I
formerly grew them in a mixture of promix and Turface, watering as
needed, and this
worked well. However, As the pots became more numerous, watering
became quite a
chore. Also, when the next dormancy occurred, finding small tubers in
a potting mix was
difficult, and I'm sure I discarded quite a few. Last year I was
introduced to another soil
modifier called Permatill. This is a fired slate product somewhat
similar to Turface, which
will absorb some water, but the particles are considerably larger.
(It's what those lightweight
"asphalt" blocks are made of.) I decided to try wet Permatill as a
growing medium,
again putting the pot in standing water, and so far it works like a
charm. I've seen no
rotting, the plants grow well, and finding even small tubers after
dormancy occurs is easy.
After the second growth cycle, three more months of refrigeration is
used (damp Turface
in a bag again), and then comes another growth cycle in wet
Permatill. After this,
management depends on the size of the tubers and whether the season
is right for outdoor
planting.
During the various stages of this process, there is always some
problem with loss of
tubers. A good rule to apply is that small tubers are more likely to
be lost by being too
dry, and larger ones by being too wet.
The above method generally creates about an eight-month "year". If I
start with seed in
the late fall, I can usually compress three growth cyles into two
years. At that point, most
species are ready to plant out, and will flower. I have had quite a
few plants flower
unexpectedly under lights, and in the past year had some Arisaema
ringens flower in their
second growth period, only eight months after starting the seed.
Now for the bad news! Not all Arisaema species are this easy. My
experience has been
largely with Japanese and Chinese species. Limited experience with
Himalayan species has
been less successful, but I think that this has been frequently due
to non-viable seed.
Some of the Japanese species (A. thunbergii, e.g.) will only produce
a radicle in their first
growth cycle, needing a cold period before the first leaf appears.
This, of course, means
that if you plant them in a pot outdoors, nothing will appear until
after two winters. I
handle them the same way initially, planting in wet Turface when
radicles appear, but leave
them in the pot for refrigeration, first allowing excess moisture to
drain and then placing
the entire pot in a bag.
Arisaema elephas remains a puzzle to me. I have tried many different
batches of seeds
from multiple sources, and have yet to succeed with it. It appears to
sometimes produce a
tiny tuber, but most of my attempts end up with rotted seeds.
The system that I have described works well for me, but it's
important to go back to my
first statement, that Arisaema seeds are easy! If you don't have
access to Turface and/or
Permatill, you'll do fine with the usual potting mixes. It's just a
bit more trouble to keep
the proper moisture levels, as well as to find small tubers when pots
are emptied. And I'm
sure that others, particularly some of the professional growers, have
some shortcuts that
I've not considered.
Information about this subject and other aspects of growing Arisaemas
is exchanged
regularly on Arisaema-L, and I would encourage all interested in this
genus to contact Ray
Stilwell in this regard.
I'm available by email (jimmcclem@aol.com) if anyone has questions
about my method.
Il giorno 12/giu/09, alle ore 09:41, giorgio pozzi ha scritto:

Giorgio Pozzi

studio.pozzitaubert@tiscali.it