I live in Ohio zone 5/6. I have a friend who has banana trees and he overwinters them by cutting them back to 6" then covering them with a foot of straw and plastic sheeting. He literally has 110 of these trees on his property and they look amazing. My question is can the same technique be employed to overwinter dahlia and ranunculus? Has anyone ever tried this? Thank you.

I've occasionally left unwanted dahlia clumps in the ground over winter and by spring they were nothing but mush. But I've never tried mulching so have no idea if that would work. I was surprised a few years ago while tilling the garden in the spring. I looked down and saw something green. It was a tuber I had apparently broken off from a clump and it had a green sprout. Must have been a mild winter because that's the only time I've ever seen that.

I talked to a couple county engineers several years ago and was told the ground freeze depth in this area is 30-36" deep. I personally don't believe it's anywhere near that. I've dug down in late winter while metal detecting and have a hard time believing the freeze is more than 4-6" deep. But maybe we're talking about two different things. But if so, it would take a lot of mulch to protect the tubers. I'd never chance it with any I really cared about.

psudan said: I've occasionally left unwanted dahlia clumps in the ground over winter and by spring they were nothing but mush. But I've never tried mulching so have no idea if that would work. I was surprised a few years ago while tilling the garden in the spring. I looked down and saw something green. It was a tuber I had apparently broken off from a clump and it had a green sprout. Must have been a mild winter because that's the only time I've ever seen that.

I talked to a couple county engineers several years ago and was told the ground freeze depth in this area is 30-36" deep. I personally don't believe it's anywhere near that. I've dug down in late winter while metal detecting and have a hard time believing the freeze is more than 4-6" deep. But maybe we're talking about two different things. But if so, it would take a lot of mulch to protect the tubers. I'd never chance it with any I really cared about.

This makes sense. Were it not for my friend with the banana trees I probably wouldn't have even considered it. But I'm thinking an experiment may be in order.

@MadHornet , I think bananas and palm trees have very deep, tough roots, so they can die back to the ground in a really bad winter and not die - as long as wet doesn't get in.

Dahlias are shallow and the tubers are filled with mostly water, and their feeder roots go out, not down. I'm in zone 8 supposedly - but when we have one of those dreaded Arctic polar windstorms, the ground freezes far enough down to kill our dahlias and other plants and it's more like a zone 6 or 7. Your zone is much colder than that.

What I think is worse than cold is WET soil or medium. I dig every year because my soil is heavy clay that turns into sticky awful mud in the winter and spring. I don't even put my tubers into the ground until June if we have a wet spring.

If your soil is sandy and sharp draining, and you cover your beds to keep them dry (ie leaves, mulch like sedgegrass or straw, and then cardboard and plastic on top to keep out the wet) you may be able to leave your dahlias in the ground. Once they develop big clumps, what often happens here in Western WA is that the top part of the clumps close to the soil surface freeze but something survives down below.

Every year i wish i could just leave my tubers in the ground and mulch and cover. The two years I left them in the ground, the rot got them and they almost all turned to mush. I ended up digging in Feb. after one of those horrid freezes to save some in the ground, at the advice of another dahlia forum i am on (cubits) - that worked. I managed to save some that I dug.

Maybe experiment on ones you don't care about that much or have duplicates? let us know how it works out.

I am experimenting this year with some of mine. I am z6 Pennslyvania...
I mulched with a thick layer of pine needles, leaves and the cut-down dahlias, covered that with a cement blanket and then a tarp. Keeping that it works.

I am not a dahlia grower, but I do have a storage question. I am overwintering a box of dahlia tubers for a friend. They are in the basement at about 60°. When he brought them, each had been air dried, then wrapped in saran wrap and taped shut. One already has begun to rot. Wondering if there is a better way to store them. They have only been here a week and I'm concerned that the entire box
is going to rot on my watch.

For rotting tubers - toss as you see them. Yes 60° is not ideal, but I do that yearly mine are in the basement of my 125 yo house which stays cooler but still is a heated basement. Sometimes you have sprouts happen w the warmth. I check monthly and toss the mushy tubers. Make sure not to store on the basement floor. I also store in plastic crates to help w airflow and not in cardboard. What are the tubers all in? Do you have a cooler corner to pop them into?