Expert Tips for Digging and Dividing Dahlias

November 11, 2015 | By | Reply More

digging and dividing dahlias

One of Lynn Rapp’s stunning bouquets featuring cafe au lait dahlia!

I suspect that one of the reasons I love gardening is that there is always something new. If you’ve conquered growing petunias in a pot, now you can move on to growing herbs. Getting good at growing perennials? Maybe you want to try growing food. My brain works in such a way that when I try something new, I am all in, learning as much as I can as fast as I can. And then, I get bored and move on to the next thing. Gardening is full of those next things, and this year one of the new things I tried was growing dahlias.

digging and dividing dahlias

One of my Arthur Hambley dahlias in full bloom

 

 

 

 

 

 

I envisioned dahlias being part of the small cutting garden I started this year – yes, another new thing! I ordered my tubers in four different varieties from Baker Creek Heirloom Seeds. The plants took forever to come up, but then they grew quickly over the summer months.

I had mixed success, as only one variety – Arthur Hambley – bloomed profusely before the frost. My anxiously-awaited Thomas Edison and Cafe au Lait dahlias were full of buds and even the beginnings of blooms when the first frost hit. But, I will try again next year and hope for better results.

Dahlias are a thrifty gardener’s dream because, although they won’t survive a northern winter in the ground, the tubers can be dug up and stored for planting the following year. And, when you divide the tubers, your dahlia stash grows quickly. Except, when the time came this year, I didn’t know how to do that.

Make a crater around the plant

Make a crater around the plant

Then, I had the awesome treat of getting a true expert to not just tell me what to do, but she came to my house to demonstrate! Lynn Rapp is the owner of Cultivating Joy Flower Farm in Oreland, Pennsylvania. I first met Lynn at the Ambler Farmers Market where she sells her beautifully-designed bouquets of sustainably-grown, local flowers. One late summer morning, I was admiring one of her bouquets at the market and I remarked, “I just love goldenrod.” She came back with, “No dear, not goldenrod. It’s solidago or no one will want to buy it!”

Since then, I’ve learned a lot about flowers, gardening, and the immense amount of hard work and dedication it takes to run a successful flower farm from our chats. I’ve even learned to stop trying to get rid of the pokeweed in my yard and instead, appreciate its lovely form which makes it a pretty addition to cut flower arrangements foraged in my own yard.

Lynn’s Tips for Digging and Dividing Dahlias

digging and dividing dahlias

My cafe au lait dahlia, all dug up

In fall, wait to dig up your dahlias until at least two weeks after the first frost kills the plants’ foliage. Cut down the stems right away but leave a few inches of stem so that you know exactly where the plants are when you are ready to dig.

Keep water from getting into the stems because the tubers are prone to rotting in the ground. I cut small pieces of plastic wrap which I tied over the tops of the stems for this purpose. Even so, I ended up with some rotted tubers.

digging and dividing dahlias

Rinse away the soil

Begin by using your hands to make a shallow crater around the base of the plants that’s about 18 inches in diameter. This will loosen the soil on top of your tubers and help reduce “broken necks” on your tubers.

digging and dividing dahlias

Prying apart the two stems

Using a big shovel, start to dig around the edge of your crater, gently prying the ground as you move around the circle.

Soon, you should be able to just gently lift the entire plant and root from the ground with your shovel. Carrying your plant from the bottom, take it over to your garden hose area and gently rinse away as much soil as possible. When the tubers are nice and clean, it’s much easier to see what you’re doing when you begin dividing and cutting. Place the tubers in the sun to cure for about 24 hours.

The white spot on the bottom is an eye

The white spot on the bottom is an eye

Now, you’ll need to work quickly – if you let your tubers sit out too long, the eyes will begin to shrink and they become harder to see. You need an eye on every divided tuber in order to get a plant next year.

If your plant has multiple thick stems, gently pry them apart with your hands, dividing the tuber mass. You will probably loss a few tubers during this process, but that’s OK. Now inspect the tubers for any that look broken at the neck. Cut these away and discard them. Then, trim off any whiskery or thin roots from the ends and around the tubers.

You will be able to identify the “mother” tuber because it will be darker brown and kind of leathery looking. This is the tuber you planted in the spring. In the photo above, the mother is on the left of the big mass of  roots. You will end up cutting away and discarding this tuber.

Now it’s time to locate “eyes” and these can be hard to see but they are actually located on the stem. Tubers are planted quite deep initially, and so a good portion of stem is actually underground. Using your hand pruners, begin to make cuts so that you have a tuber and an eye for each.

If you notice any dark rotten spots, cut those away as you would with a potato. You don’t need to have the entire tuber intact.

Once you have divided up your tubers, lay them in a sunny spot for 48 hours to cure. The cuts you made will have formed calluses and the tubers will be nice and dry for storage.

After 48 hours of curing, tightly wrap each tuber individually in plastic wrap, label the outside so you know the variety, and place in a shallow box, milk crate, or Styrofoam cooler. With this method, there’s no need to leave space between the tubers because they can’t touch each other once they are wrapped in plastic.

Some of your divisions could have an eye and two smaller roots

Some of your divisions could have an eye and two smaller roots

Place the box in a cool, dark place for the winter. I will put mine in our unheated garage. If you have an interior wall in your garage, place the box against it so it will stay slightly warmer.

In the spring, Lynn has promised to teach me all about planting my tubers properly in the hopes that I will have better luck with blooms next year. That will be “Part Two” of our dahlia series. Those stunning Arthur Hambley’s were enough to get me totally sold on dahlias, but I surely can’t say I’ve mastered growing them yet!

 

 

digging and dividing dahlias

Lynn Rapp and me

 

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Category: Flowers, General, Home and Garden

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