How to Overwinter Tender Bulbs, Tubers, Corms, and Rhizomes

When I lived down South in zone 7, I rarely ever lifted bulbs for the winter unless I wanted to move them or share them.  I was usually able to get away with piling extra winter mulch on top of tender bulbs and that would get them through, even if they were only hardy to zone 8.

Calla Lily, hardy to zone 8, overwintered in zone 7 with protective winter mulch

Now I'm up North, though, and, sadly, extra mulch just doesn't cut it.  Those tender bulbs (or corms, or tubers, or whatever they might technically be named) have to be lifted and packed away for winter storage and then replanted next spring.  Here are my steps for lifting and storing them:

1.  After the first good frost, cut off the browning foliage and carefully dig up the bulbs, avoiding bruising them.  Gently brush off excess dirt.

Digging up Gladiolus murielae corms

2. Dry in a warm, well-ventilated place for a couple of days.  Corms such as Calla Lily, Crocosmia, Freesia, Gladiolus, Tigrida, and Tritonia need to cure in a warm place for longer, about three weeks.

Sometimes those corms will have lots of little baby 'cormlets' on them.  Just separate them gently from the main corm.  You can keep them for planting next year if you like; they will eventually grow big.

a corm with lots of little baby 'cormlets' attached

3.  If your storage area is humid, you might want to dust the bulbs with an organic fungicide.  (I've never done this, though, since my storage area is thankfully pretty dry.)

4.  Store in paper bags or cardboard boxes filled with peat moss, sand, vermiculite, or sawdust.  Gladiolus can just be stored in paper bags or onion bags, or in a box between sheets of newspaper.  For some tubers and corms, such as Dahlias, Foxtail Lilies, and Rain Lilies, the peat moss or other medium should be very slightly dampened, so that they do not completely dry and shrivel up.

Don't forget to label your bulbs!

Just make sure you don't store the bulbs in enclosed plastic boxes or bags, as that will keep in moisture and cause them to rot.

5.  Store in a cool, dry place, around 40 to 50 degrees.  Check on the bulbs a couple times during the winter.  If the bulbs are shriveling up from dryness, give them a mist.  Discard any bulbs that are getting mushy and decaying.

6.  Plant next spring...

Dahlia 'Kelvin Floodlight'

... and enjoy!


Here are a couple other resources that list how to store different kinds of bulbs:
A.D.R. Bulbs: preserving summer bulbs
P. Allen Smith: storing summer bulbs