Updated: Feb 28, 2022
To Everything There Is a Season
There's nothing quite like a field of flowers in full summer glory. "Farmer Andy" spends his mornings in late June through October walking between the rows, making bouquets for our flower stands. Its a very peaceful way to start the day.
But eventually (usually a couple weeks after he gets real tired of picking flowers), in comes the first killing frost of fall. This year my dad (farmer Andy) watched it happen early one morning in mid November. Over the course of an hour, every single plant and bloom frosted over in one last dazzling display before giving up the ghost.
Removing stalks and ground cover
Once a killing frost hits, dahlias need to remain in the ground for 1-2 weeks. This lets the tubers develop a skin that helps them survive winter storage.
Once they've hardened up, the next step is to cut off the stalks and cart them to the compost pile. Andy's antique Farmall Cub (which he restored himself!) helped with that.
It's important to remember not to lose your markers when you cut off the stalks. That's how you wind up with mystery dahlias!
Next year we will be planting all in blocks of at least 25 of the same variety, which will eliminate most of the need for marking individual plants.
But this year, we cut the stalks as low as we could without losing our marking tape, then carefully pried up the ground cover, which we rolled up neatly and put away to use again next spring.
Digging up (lifting) dahlia tubers
The most strenuous part. We use potato forks (and a pitchfork or two). Dahlia tubers don't grow too deep, but they can grow wide. Make sure to place the digging fork about 12" away from the stalk; push the fork in all the way; then lift. Shake off what dirt you can gently but don't get too frisky. Many dahlia varieties grow tubers with very delicate necks, and if you break any necks, the tubers attached will be useless.
We got a little overzealous during our first 10-hour harvesting day and dug up a few too many clumps all at once. We had to hoof them all into the barn wherever they would fit in order to save them from freezing temperatures aboveground the next night.
We lifted about 2/3 of our field the first day. In retrospect, it would have been more efficient to lift only as many tubers as we could wash in the same day so that we wouldn't have to worry about hoofing them all into the barn ahead the frost.
Washing the dahlia tubers
It's a chore, but washing tubers is important. It's impossible to see the germinating eyes if they're covered in dirt, which means you can't divide a dirty tuber clump. Washing also helps reduce the spread of any diseases from one isolated clump to another (we've never had a problem with disease, and we'd like to keep it that way!)
Some growers store the clumps in their dirt all winter and divide in spring, when the eyes are easy to see. But we like to be done early. Plus, we don't have enough space to store tons of undivided, unwashed tuber clumps - so we had to do the job in the winter. As you can see in the photo above, clumps take up a lot of space!
We washed our tubers outside on a sifting frame (just a wooden frame with wire mesh attached) using a garden hose. High volume is preferable to high pressure - too high pressure can rip the protective skin right off the tubers.
This can be a very cold and wet job in November, but it's much improved with cheap rain gear (we like Frog Toggs), rubber boots, and waterproof insulated gloves. Plus, it ain't a bad office!
Dividing dahlia tubers
The longest part of the job. Linda (mom) is a patient woman - who else would let us process thousands of pounds of field produce in the living room!? She even helped. Maybe just to get us out of there faster... Dividing tubers makes a lot of compost. Anywhere from 40-85% of the total mass of the tuber clump can't be used because they don't have eyes. Even still, dahlias are a generous plant. Some varieties gave us as much as 8 useful tubers for each tuber we'd planted in the spring. Paired with a few stingy breeds that barely gave us two tubers back, we came out with an average of about 3 tubers harvested for every 1 tuber planted.
Dividing tubers is a long, repetitive process. We watched a lot of YouTube! And made sure to clean up very, very well. We don't want to lose living room privileges next year.
Once the tubers are divided, we wash them again and leave them out to dry. Home gardeners can wash divided tubers in the sink (be sure to use cold water), but we washed with a hose outside in plastic produce crates, then stacked those crates in the garage in front of a fan.
Be careful when drying tubers, especially if you use a fan to speed the drying -you want them to be dry on the outside, but not to lose any moisture from the tuber itself. Check them every couple hours. You want to put them away before you see any sign of shriveling.
If you do mess up and your tubers shrivel a little, it's not the end of the world. But remember, they have a long winter to get through, so you want them to have as much chance of survival as possible.
As for storage: everybody's got their favorite storage method. Andy has tried several, and hit on a winner for us.
We store our tubers in clean, dry 5 gallon buckets (preferably all the same size so they can be stacked), leaving 2-4 inches of headroom in each bucket, which we fill with a generous amount of newsprint. The buckets are carefully labeled, stacked, then stored in our garage, where the temperature stays around 38 degrees all winter (our tubers would be very unhappy in the unheated barn). They stay nice and snug in their buckets until the spring, when its time for their next adventure...
All in all, it took two people 8 full days of labor (128 manhours) plus some much appreciated drop-in volunteer hours to process the harvest from 2000 dahlias planted in the spring.
We expect to triple our field size next year. We may be tubering all winter long!