Ed Bonci, a master gardener who lives in Eastchester, sent me a note about a class he’s teaching on how to overwinter dahlias.

Ed is nuts for dahlias and a very enthusiastic, knowledgeable teacher about how to care for them. I heard him speak last year on the same topic, same place—very worthwhile.
Here’s Ed at last year’s class. (photos by Liz Orozco and Ricky Flores)

His note about the class this year:
“I’ll be giving a dahlia tuber digging, dividing and storing demonstration at The Hartsbrook Preserve on Monday Oct 29th @ 10:00 AM.
If you or anyone you know would be interested in attending, please feel free to pass the word along and come join me.
It should last between 1-1.5 hrs and will be similar to what you attended last year.”
Here’s a Web site with directions to the Hartsdale park.
And here are excerpts from the article I wrote for the paper after attending the workshop last year.
“If you want your big-blooming dahlias to return for another show next year, you have to dig them up now and get them into storage for the winter.
Many gardeners say, “Hey, I’m way too busy for that,� and just assume they will start fresh next spring with new plants that catch their eye. But it’s really not that hard to save them from year to year and certainly worth it if you were happy with the ones you had this year and don’t want to take the time to find them again.
Dahlias, like other summer bulbs and tender perennials such as cannas, begonias and gladiolas, are simply not hardy enough to survive winters in the Hudson Valley. Leave them in the ground or in pots on the deck and the first hard freeze will kill them.
To save your dahlias, you need to dig up the tuberous roots after a frost blackens the leaves. Then clean the tubers and store them in a cool place for winter.

Ed Bonci, a dahlia expert who grows about 100 different varieties in raised beds in his Eastchester yard, suggests waiting a week after the first frost before digging them up. This allows the “eyes� in the tubers to swell a bit so that you can more easily identify them when you’re dividing the uprooted clumps.
Before you dig, cut back the stem to a length of 4 to 6 inches; this gives you a good handle to work with as you pull up the clumps.
With a shovel or pitchfork, dig a circle that extends 8 to 10 inches away from the stem. Gently lift up the clump of tubers and roots and shake away as much soil as you can. Rinse away the rest with the soft spray from a garden hose.
Let the clumps dry out overnight, in a place where they won’t freeze, to allow the protective skin on the tubers to harden. Bonci, who led a demonstration on dahlia care on a warm morning last week at the master gardeners’ demonstration gardens at the Hart’s Brook Park and Preserve in Hartsdale, just lets his dug-up clumps sit on the grass for a day.
Noeline and Rocco Vicini, who grow dozens of dahlias each year in their Mahopac garden, let their dahlias dry out for a week to 10 days on a huge piece of plywood on the floor of the garage. Then they pack them into 17 wooden crates and store them in a cool room in the basement.
While the tubers are drying, the Vicinis also divide the tubers and cut away any spent or dead parts.
Bonci likes to get it all done as quickly as possible, and he’s pretty ruthless about throwing away any thin or weak-looking tubers and all hair roots within a large clump.
“As long as I get two or three viable tubers, I’m good,� he says.
He uses a sharp knife and clippers to cut apart the clumps and find the plump tubers worth saving. He then dabs the cut parts with a fungicidal powder to prevent rot.

“Each tuber has a body, neck and crown,� Bonci explains. The crown, the part that’s closest to the stem, contains the eyes that will be the source of next year’s new sprouts.
Each of your saved tubers needs to have at least one eye. In the fall, they are just small bumps that are difficult to see.
“If you cut off enough of the crown, you’ll probably get an eye, even if you can’t see it,� says Bonci, who works nights as a pilot for DHL (“I’m a pilot by night, a gardener by day.�)
Many gardeners like to wait until spring to divide their dahlias because it’s easier to see the eyes. In that case, you can just overwinter the whole clump. Bonci, who is a member of two dahlia societies on Long Island and one in Connecticut, recommends storing it upside-down.
He says it’s also important to keep track of any plant tags while you’re digging and dividing so that you can identify what you’ve got come spring. He writes right on his tubers with a Sharpie marker.
To store them for winter, Bonci sorts the tubers by variety into 1-gallon plastic bags and adds a couple of cups of vermiculite and a couple of teaspoons of fungicide.
“Never use peat moss,� he says. “It wicks away most of the moisture and the tubers will shrivel.�
He leaves the plastic bags unsealed and stacks them in newspaper-lined cardboard boxes that go up to his unheated attic for the winter. He checks them periodically to remove any rotten tubers before the fungus can spread. As a memory aid, Bonci recommends winter holidays: Christmas, Valentine’s Day and St. Patrick’s Day.
The ideal temperature for storage ranges from 38 to 50 degrees.
“If you don’t grow a lot, the best place to store your tubers is your refrigerator,� Bonci says. “Put them in the crisper inside a plastic bag. That way you can check on them whenever you want.�
Once all threat of frost has passed in May, your stored dahlia tubers can go right back into the ground.
After a few years of mixed results, Bonci says he’s had 100 percent success with his storage method the past two winters.

John Dusza, a great dahlia grower in Nanuet, is more cavalier about his approach.
“I’m very good at buying them from catalogs, not so good at storing them,� he says with a laugh. “I only get a 10 to 15 percent survival rate.�
He wraps the tubers from his 90 plants (down from 250 just a few years ago) in newspapers and then sets them into cardboard boxes that go into his unheated garage.
“I just hope for the best,� he says. “Most of the time, it stays just slightly above freezing in there. Some varieties come back just fine every year no matter what you do to them.�
Here’s a 2002 photo of John that I found in our photo library.

Rather than taking the time to divide them in fall, Dusza prefers to wait until spring to see what survives.
“I’m just so damned tired after digging them up,� he says. “I have two seasons, one in the garden and another in my wood shop. When frost takes my dahlias, I say, ‘Good riddance!’ Then it’s time to get to my wood shop for the winter.�
