Expert: Long Island Gardener - 10/7/2006

Question

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Followup To

Question -
Zone 5
This summer I grew several Calla Lillies in large pots. I'd like to
save the bulbs and replant next spring. I've read (or heard) that
peat moss is a good medium for storing them - but - what do I
do about the roots? Should they be trimmed back? Should the
bulbs be rubbed clean of the dirt that's on them? Also, some of
the bulbs got huge over the summer. I guess that's okay - right?
Thanks,
Ron

Answer -
Ron, one of the premier Calla Lily specialists, FlowersBulbs.com
(www.calla-lilies.com/index.cfm), has this Calla overwintering
advice - called "curing" in the trade:

"Wash tubers gently to remove soil. Then dip tubers in an
appropriate fungicide solution (e.g. Kocide) for 5-10 minutes.
This helps to eliminate fungal pathogens. Dry tubers within 4-6
hours with air assisted fans if need be. Subsequently cure bulbs
for 3-7 days at 70-80°F, ensuring good air movement. This
curing stage is important in forming an outer skin on the tuber,
which acts as a barrier to dehydration and disease. Store tubers
in a single layer on mesh trays at 45-50°F for a minimum of two
months prior subsequent plantings."

I think you can skip the part about treatments with fungicide -
in fact, it is probably MUCH better to do that, because that stuff
is strong and who knows what weird side effects you'll end up
with down the road?

But the curing and air movement is a tricky exercise, one that
will come in handy, with a few small custom changes, with
Dahlias, Gladiolus and other tender bulbs.  It's a long term, all-
winter-long care project; it's not unusual for people to lose
interest after the first few months of waiting and watching inert
brown things to make sure they are still intact and undamaged.  
Definitely worth a try.

And if you don't succeed at first, it's not a bad thing, just a
learning experience.  The best kind of learning there is.

Need clarification on any of this?  

Answer
Sorry I failed to mention the peat moss detail, Ron, and instructions about your roots.

Some growers use peat moss, others use their own custom mixtures.  Potted in autumn, dormant Calla rhizomes will form roots if you keep them moist and keep them 50 degrees F. They need less water over the winter.  But don't let them dry out. And "pruning" roots is a no-no.  

After they flower, you can induce dormancy by reducing water little by little.  Or they can be set outside in warm weather and grown in pots with rich, humusy soil and occasional watering to keep them from drying out.  Not until leaves begin yellowing should you stop watering them.  Rinse them to remove old soil before repotting.  Renew soil every growing season.

I hope this helps.  Let me know if I've missed something else.