What is the maximum planting depth for dahlias?

steve22802(7a VA)June 26, 2006

Hi all,

I read recently on GardenWeb that some people in colder zones have been able to get dahlias to overwinter in the ground with extra protection like heavy mulch or strategic microclimate placement. What I'm wondering is whether or not I can gain some extra protection by planting them deeper. So does anyone know what the maximum planting depth is for Dahlias? Could I plant them as deep as 12 inches? I learned last summer that callas can be planted as much as 12 inches deep for extra protection. Also would it help to cover them for the winter with sheet plastic to help keep them dry?



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I see no one has answered this yes, but yes, you can plant dahlias 12" deep in good, friable soil. I'm talking about regular dahlias, not speaialty show-quality dahlias which I know nothing about.

You lose a month the first year -- in other words, they bloom a month later than if you planted them the regular depth.

I'm not fond of plastic coverings, and I don't think you need to keep them *that* dry over winter...just go on your normal business and they'll come up in spring. It tales awhile, BTW, so don't think they're not there because they are -- waaay down there.

FWIW, I have noticed that when I water in the dry summer, I have to water really, really deeply. Makes sense when you think about it.


    Bookmark   August 6, 2006 at 11:20PM
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All my dahlias came back without any special protection. I live in Maryland, not far from you. I did not even mulch them. May be some varieties are more tender than others. It seems that nobody here tried deep planting for winter protection. So if you will experiment with this method, please share your experience next year! Good luck!

    Bookmark   August 7, 2006 at 10:37AM
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I disagree with planting them so deep. Plants have been nurtured to act in a particular way and that includes how deep in the soil they are placed.

Hence, tulips, while doing fine down 6", do not suffer if 8" is put over their heads. But, put a tulip down 2"...see what happens...
or put a glad down 2"....nothing but trouble.

Plants do their best when given their due attention.

While sometimes we get away with inattention to our perennials and bulbs and tubers, we nonetheless recognize what we should have done to best protect them.

Its all well and good to say "I left mine in the ground and they came back as good as ever in the spring"....but...what was the winter like....if it had been more a severe one, might the tubers have suffered differently.

And it always amazes me when people tell other people about how they treated their perennials.....and expect everybody else to have the same results.

Where there is doubt, then do right by the plants and lift and store. Imagine if the winter is a cold one...and mulching before the time you should---AFTER a hard frost---causes the ground to stay warmer than it should...the ground is being prevented from going dormant...the plants within may even be pushed to grow new leaves...and then reality sets in...and the plant suffers.

I figure zone 7 is border country. You takes your chances either way.
If the plant can be stored properly in a cool environment, then why even question it. Its no big deal to dig AFTER the hard frost, let the tubers dry for a day or so, then put them into a cool place in a bed of peat moss, sand or vermiculite.

Or...read the article in the Dahlia Society site....about how to remove each tuber from the clump, and cocoon them in plastic wrap---then store them in a cool place.

    Bookmark   August 13, 2006 at 6:00PM
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I have a gardening friend who had HUGE gladolias in early June this year at church. I asked him how on earth he got blooms so early, much less so huge. He says he does not lift them. HUH? I thought that was an absolute in our climate. Not so - you have to bury them 24" deep in leaves (he puts up fencing around his bed in the fall), but they do fine. So I'm going to experiment likewise with a few of my dahlias. If I lose them, no big deal. But just goes to show you that what we thought was the gospel of gardening isn't ALWAYS the case.

    Bookmark   August 23, 2006 at 8:17PM
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Chemocurl zn5b/6a Indiana(zone 5/6)

I have been pleasantly surprised when 2 different patio dahlias came back 2 springs, with no extra protection. We had some very cold temps, but there was snow cover at the time. Also, they are planted near a south facing brown brick wall.


    Bookmark   August 28, 2006 at 5:48PM
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