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From: "Andy Y.S. Wong" <asiatica at EZONLINE.COM>
Subject: overwintering arisaemas
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> I think that Barry Yinger and Andy Wong (Asiatica Nursery) use dry
sphagnum

Some observations from Barry Yinger and Andy Wong.

This is actually a very complicated topic.  We have been observing the
process of dormancy and how corms behave when dormant for several years,
and we are learning more and more about this critical issue.

1.  It is extremely easy to overwinter young corms; they almost never
rot under most conditions; the larger the corm the easier it is for them
to rot.

2.  If the corms are kept cold, large corms do not benefit at all from
moisture when dormant; moisture can only cause trouble.  We use dry
sphagnum mostly to draw any moisture away from the corm and to cushion
the corms in storage.  We keep them around 40 degrees F in cardboard
boxes with excellent results.  We also store potted arisaemas in their
pots, just allowing the mix to become completely dry, and stacking them
in flats for the winter in cold storage. A household refrigerator is
fine for winter storage of corms, in plastic bags with holes, packed in
dry sphagnum. (This doesn't work with subtropical species; I think they
need to be kept warm all the time).

3.  The ability of a corm to make it through the winter without rotting
depends partly on how it passes through the process of going dormant.
Corms must be properly "cured" to store well.  This is a process of
gradually reducing the moisture content of the corm.  Some growers plant
annual herbs in the pots to draw moisture away from the corm in late
summer.  In the garden, you can plant corms among perennials and ground
covers to draw moisture away in late summer to help the curing process.
Cured corms can be soaked in a ten percent bleach solution and dried
before storing.  This is especially important if the corms are damaged
in digging.  We almost never lose corms that are completely cured and
properly stored; the period from the onset of dormancy until they are
cured is when they are likely to rot.

4.  Predation by certain pests such as fungus gnats and maybe mites and
thrips seems to increase the chance of rot while the corm is entering
dormancy.  We never use peat moss in growing mixes because it seems to
attract fungus gnats.  We use a compost called Biocomp BC5 and almost
never have fungus gnats.

5.  The most dangerous period  for rotting is when the plant is in the
process of going dormant.  Large plants in particular often succumb to
what seems to be a bacterial crown rot.  This is more of a problem in
pots than in the garden.  We rarely lose corms in the garden, but have
to watch the potted plants carefully.  Bacterial crown rots spread
quickly and easily in summer among potted plants.  I think this is why
many people report losing potted plants and those grown together in
nursery beds. The combination of heat and high humidity is very
dangerous.

6.  There is a tremendous variability in the resistance of different
species to rotting.  Some of the resistant species are triphyllum,
ringens, heterophyllum, candidissimum, saxatile, ternatipartitum,
urashima.  Very sensitive species include sazensoo, sikokianum,
thunbergii, yamatense, kishidaa.

7.  If corms are bruised, cut, or frozen, they are not likely to store
properly.  They must be handled very gently until completely cured, then
they will take a certain amount of abuse.

8.  If you find a soft or bruised spot in storage, cut away to firm
white tissue and soak the corm in bleach solution and dry completely.

9.  We don't water potted corms until the shoots emerge in spring.

10.  In warm, moist summer climates, be prepared to withhold water in
late summer and treat for bacterial crown rot.  I think that fungus
diseases caused by Sclerotinia are also a danger.

We hope this helps.