Dividing and Storing Dahlia Tubers

By Annie P (Poochella) on October 27, 2014

One killing frost or waning days sunlight will bring the year's dahlia blooms to an abrupt or dwindling end. Now is the time to ponder some techniques to successfully overwinter your dahlia tubers. It isn't difficult, and some lucky gardeners can get by without digging their dahlias at all. If you're in Zone 7 or less, and want to see your most treasured dahlias again, ready the shovel and read on...

Digging and Dividing Dahlia Tubers

It can happen in a flash: one sly frost or deep freeze will turn your beautifully blooming, tender dahlias into unrecognizable masses of cooked spinach hanging limply on their stalks with blooms robbed of color overnight. If you want to preserve them for next year, with correct IDs, the time to act is now .   This article will cover steps you can take to assure a chance to fill your garden beds with your favorite dahlias next Spring. 

If you garden in Zone 7a or less, or in a very wet climate, chances are you will likely have to dig and store your tender dahlia tubers for winter.  Hats off to those of you that don't!  The process isn't difficult, but can take some time,practice, and experimentation.  Even if you don't have to dig, it is a good practice to divide a dahlia clump at least every three years for the health of the plant and to keep the clump a manageable size. This is how I've gone about it in my very wet Pacific Northwest soil each autumn.  The best method for your area's dahlia storage will be found with a little trial and error.  Don't put your eggs in one basket: try different methods, and see what works for you!

USEFUL TOOLS FOR DIGGING AND DIVIDING DAHLIAS

Transplant shovel or garden shovel- severs long roots around the clump

Garden fork- loosens soil and lets soil drop off when lifting clump, less tuber breakage

Lopping shears, PVC cutter, or stout pruning shears- useful in cutting off thick stalk

Thin bladed snips, pruning shears or stout knife - for severing single tubers off clump

Hose with adjustable nozzle settings- to gently rinse tubers

Marking pens, pencils- Sharpies on dry tubers, No Blot Ink Pencils on wet tubers

Bucket, water, bleach or fungcide - provides a final antifungal rinse of individual tubers

Raised screen, rack, or newspapers to dry tubers- allows skins to dry and toughen.

Storage media or method- coarse vermiculite, wood shavings, sawdust, peat, plastic wrap.

There are about as many ways to process and store dahlia tubers as there are dahlia varieties.  Finding a way that works best in your conditions is a matter of experimentation.

        

Dahlia dividing arsenal

You can read about waiting until a killing frost before one digs their dahlia tubers, but some areas won't get a killing frost until late, or ever.  I have had good luck just cutting the plants off, letting them sit for anywhere from a  day to a week and then getting about the unearthing and preparation for storage.  Either way works equally well here.   Once, you've cut your plants down, or Jack Frost has visited, it's time to move on to digging and dividing the harvest underground.

 

Digging and Dividing Dahlias

One lone dahlia tuber will generally send out roots that fatten and store nutrients through the gardening season to become next year's tubers, . You can store clumps whole and divide them in spring when evidence of new growth is evident; or to save space, you can divide the clumps into single tubers or small groups of tubers for winter storage.  Do what works best for you and your storage space allowances.


Digging the clump

 

Use a transplant or sand shovel to cut deeply around 3 sides of the severed dahlia stalk, about 8" away from the stalk.  Tubers can send out long roots that will pull on delicate tuber necks and break them if you don't cut them prior to lifting out of the ground.  The final shovel or fork is used to dig deeply and lift the clump.  Note the plant's tag has been moved from the stake to the stalk base to preserve the plant'sidentification.  There is nothing worse than waiting weeks for a certain flower, only to grow a flower on the opposite eside of the color wheel, and not the form or size you ordered!

I store single tubers, or small groups of tubers for space-saving purposes.  The clump will need to be rinsed off quite thoroughly, again keeping the tag intact with the clump. Don't use such force that you break the tender skin of the tuber which can be a gateway for pathogens; just rinse as much dirt off as you can.  By November, our Northwest US soil is soggy as can be, and I can't overemphasize how clingy Miracle grow potting soil with soil polymers is on a pre-potted tuber and the clump it may produce.  It takes three times the amount of water and time to rinse clumps started in that soil as other potting soil.  I'll never use it again, at least for dahlias.

Tag the dahlia clump

 

Once washed, you can inspect the season's tubers and decide which candidates are suitable for preserving. Disregard anything with a broken or very thin neck; or tubers thinner than about one half inch at their widest diameter.   You can try to save thinner tubers, but chances are lessened for successful storage. LABEL, LABEL LABEL.  The first thing to do facing a freshly rinsed clump of tubers is to label a tuber or two in case the tag falls off.  A lot of dahlia tubers look alike, better safe than sorry if you have to pick up that stray tuber that flew off when cutting it from the clump with no name.  There are only two dahlia vendors I've bought from that didn't at one time send mislabeled tubers. It happens in a flash.

WHY DIVIDE DAHLIAS AT ALL?

1. Better health of the plant as tubers reproduce annually, crowd and rot and fight for nutrients in an ever more crowded root zone.

2. Divide and grow more of a favorite variety.

3. Trade, gift, or sell your extras.

4. Avoid the hassle of the Monster Clump left in the ground several years!  A photo is worth a thousand words.  Below see a typical clump after one season, two years, and 3 years in the ground.  It's much easier to deal with a well-behaved clump of roots than a 40 lb mass of stems, roots and crowded tubers all snaked together.

How fast dahlia clumps multiply annually

 

Once out of the ground and rinsed of most soil, it's time to tackle DIVIDING THE CLUMP, if one chooses to divide at all.

The cleaner dahlia clump

 


A TYPICAL DAHLIA CLUMP Above, you can see the darker, aged 'mother' tuber labeled from the year before (lower left) and her offspring produced in the current season. Pruning shears on right for cutting stalks or easily severed tubers, a fruit secateur shears with very thin blades for getting a precise cut between crowded tubers or spaces. The pencil I use to mark tubers is a Sanford 705 No Blot Ink in a Pencil, permanent blue pencil that works great on damp tuber skins. Sharpie markers work great on dry tubers. ***Sanford has apparently discontinued manufacture of the cherished No Blot 705 pencils!*** I hope it's not true, they were great! Find a possible replacement here. No experience using that particular pencil on dahlia tubers; try at your own risk. Other suitable writing utensils might be found at wordworking websites, log home- building websites where writing on damp wood is mentioned.

One can store the dahlia clump whole, halved, quartered, or divided up into individual tubers or small clumps of tubers.  If opting to store a whole clump, cut off as much green stem as possible to avoid that moist material contaminating the tubers.  Anything green is prone to rot over winter, and that rot can easily spread to the tubers.

If quartering or divding your clump into parts, allow the cut surfaces to dry to touch before storing.  Allow all tubers whether single or clumps to dry to touch.  It is advised to dust cuts with a fungicide or spritz of Lysol spray.  I use Hi Yield wettable sulphur dust on cut portions of tubers, either neck end or tail end, or gashes from errant shovels.  If you are allergic to sulfa drugs, stay away from sulphur products.

 

Anatomy of a dahlia clump

If you haven't met a clump of dahlia tubers before, here is a quick review.  The most important part for propagation purposes is the collar or thick tissue below the stem or stalk from where new tubers will spring and the all-important eyes yielding next year's growth will form.  Necks lie below the collar and above the fattened main part of the fleshy tuber where nutrients are stored.  Tubers are prone to breaking, dehydrating, or rotting if too thin.  A tuber with a broken neck should be discarded.  The main tuber body and roots forming off it have nourished that tuber as it stores nutrients to support next year's sprouts.   All the roots can be trimmed off for storage, but keep the collar with eyes, neck, and tuber body in tact for best storage results.  Extra large or long tubers can be safely trimmed on the root end to a reasonable size.  Trimmed tubers keep well, as long as the cut flesh is allowed to dry to touch before winter storage. 

What lies beneath: dahlia tuber basics

 

If you store whole clumps, trim off stems, roots, allow excess soil to dry and put the clump in the storage media of your choice.  People prefer various storage media for tubers: plastic wrap, peat moss, coarse vermiculite, wood shavings, sawdust.  I have had the best luck in vermiculite and cedar shavings.  Peat moss can dehydrate tubers, plastic wrap can trap excess moisture, but has worked well for many.  Again, the best practice is the one that works for your storage area and humidity levels. Whether storing whole or dividing clumps or tubers, they must be prevented from prolonged freezing: ideal storage temps being between 40-50 degrees F.

 


Related articles:
dahlia eyes, digging and dividing dahlias, digging tubers, overwintering dahlias, storing dahlia tubers, tuber storage, winter storage of tubers

About Annie P
After growing hundreds of dahlias for 16 years, I will publish much of what I learn and cherish about these beauties and their care here. My own emphasis is on cut dahlias for the floral industry. I sell the blooms to support this hobby-gone-wild, but also share the many eye-popping flowers for friends to enjoy. I do not show dahlias for judging, as I somehow find such scrutiny insulting to otherwise perfectly gorgeous blooms! Sorry. It's not my thing.

With very little know-how and a bit of spare time, you too can enjoy the best from your dahlias whether for personal enjoyment, sharing, selling, or showing. There's no time like now to get started with dahlias!

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Comments and discussion:
Subject Thread Starter Last Reply Replies
Fantastic Info! nap Dec 10, 2014 11:20 AM 4

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