Refrigerator time

[McClements, Jim]

AEG'ers

One of the things that should evolve from our having our own list is that we
can post some of the minutiae about Arisaemas and their cultivation without
fear of boring the tropical Aroiders. (Not that they haven't done their share
of that!). So here goes!

A few months ago there was an exchange of opinions about what was the minimum
time, or ideal time, for refrigeration of arisaema corms to provide the
"artificial winter" that many of us use in an effort to shorten the time from
seed to flowering.

Craig Stubbs felt that he would be reluctant to use less than three months,
since it worked well and that even if a shorter time was sufficient to start
a new growth cycle, the plants might not be as healthy or robust. (Craig, I
hope I'm not misrepresenting your thoughts).

Tony Avent said that he'd been using only one month's refrigeration, and that
it seemed to work well.

I decided to run a little experiment. On 9-8-96 I refrigerated 24 A.
sikokianum corms that had just gone dormant after their first growth cycle
from seed. 12 were removed from the bag and planted under lights on 10-16;
the other 12 were planted under the same conditions on 12-16, 2 months later.

The 12 refrigerated for slightly more than one month came up 12-22, more than
2 months after being replanted.

The 12 refrigerated for 3 months came up 1-4-97, only 3 weeks after
replanting.

Thus, it would appear that one month may be sufficient cold, but that there
is a built-in delay in initiating a new growth cycle even if the cold is
discontinued, and that not much time is saved.

However, at least in this one instance, the ones with the SHORT cold period
are LARGER and MORE robust than the others!

An interesting addendum occurred yesterday. I opened a bag of refrigerated
corms of A. sikokianum X takedae (F2) which has been cold for 6 months, and
found all of them with one inch sprouts, again indicating that we can't keep
"fooling Mother Nature" forever by keeping corms refrigerated.

Conclusions:

1. One month's refrigeration is probably enough cold to allow the corm to
"think" that it has experienced a winter. However, the latent period between
replanting and emergence is prolonged.

2. Refrigeration beyond three months probably gains nothing, and at some
point the corm will break dormancy even if in continuous cold.

I'm sure that plant physiologists can provide some logic to these
observations. Fire away, everybody!

Jim McClements