Expert: Long Island Gardener - 10/11/2008

Question
when is the best time to cut back my dalias and split them as ihave left them in the ground for the past 4 years and they have come up every year no problem,but they are getting so thick .i feel they can be split now.also when splitting what is the best part to split.thank you katrina

Answer
Sounds like you are doing a fine job, Katrina.  Pat yourself on the back for me.  This is tricky; you have mastered it.

Divide like so:

Wait for a freeze to turn the leaves black.  Then, using a pitchfork and pruners, slice stalks about 3 inches long, loosen the clump carefully, and dig the entire clump up.

I must warn you: BE CAREFUL.

DO NOT YANKE the stem.  DO NOT break the tuber.  Keep everything intact and damage free.  Dig VERY 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.  Now we are ready to divide.

Use a sharp knife or scissors to divide the clumps in half.  The Swan Island Dahlias website posts pictures of the whole exercise:

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.

Dahlia disinfectant will increase your odds of success.  Soak 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 aretard mold.

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.

Tricky.  But not impossible.  You can do this.

THE LONG ISLAND GARDENER