Expert: Long Island Gardener - 10/29/2006

Question
How do I winterize Dahlia Bulbs?

Answer
Assuming you are in Zone 7 or cooler, you should rush out to the garden with a pitchfork and pruners and slice off the stalks about 3 inches long, then loosen the clump carefully.  Then next weekend, assuming first frost has come and gone, dig the entire clump up.  

And I must warn you: BE CAREFUL.

Don't yank out the stem, don't break the tuber, keep everything intact.  Dig gently, roots, stems and all.  

Spray the clump clean with a garden hose and cut the roots off.  Set the clump in a basement or heated garage and let it all dry.  You can store it just like that, or you can give "Division" a try.

If it works, you'll have multiple Dahlias from a single original tuber.

Use a sharp knife or scissors to divide the clumps in half.  The Swan Island Dahlias website posts pictures of the whole exercise (http/www.dahlias.com/index.asp?PageAction=Custom&ID=2#13).  Each tuber has one or more eyes - just like potatoes, which by the way are also tubers.

A Dahlia disinfectant will increase your chances of success at dividing.  Soak the tuber pieces in a solution of one cup Bleach + 3 gallons of water for 30 minutes.  Lay them out on newspapers to dry.  Some people use plastic bags with vermiculite.  I prefer to keep them in peat moss in the basement in an open plastic container.  Don't seal the container with the goal of keeping moisture in; they need air to breathe and to keep mold down.

Dahlia hybrids vary - a lot - in how much they cooperate with your division project.  Some have several eyes and resist rotting, happily yielding several healthy tubers where only one grew before.  Others rot like some people sneeze and are stingy when it comes to forming eyes.  Now you know why a single superhybrid premium tuber with dazzling genes can fetch $40 or $50 while others are $2.99.  Supply and demand.

Keep your tuber collection in the dark, someplace frost free, mist it twice a month to keep it from drying out - you don't want any shriveled tubers at the end of the winter - and wait for spring.  See how it all goes.  And don't forget to let me know.  Any questions, I'm here.