Dahlias

Question from Randy:

Thanks as always for answering my many questions. Seems like I never run out of them. I looked up in your book about storing dahlias and I waited until they browned out and carefully dug them up. I shook the soil from them and put them on a counter in the garage for two weeks. I was a little confused by your book about how exactly to store them and recalled that once when I used perlite it seemed to desiccate them. Sometimes simply putting them in a loosely tied Von’s bag worked other times not. It seems as if in the past I’ve had mixed results with all methods. Anyway, after two weeks on a counter in a cardboard box with no medium, some of the thinner ones dried up and seemed rotten. What exactly should I have packed them in? thanks.

Answer from Pat:

Dear Mr. Greenjeans:

I sympathize with the problem you’ve had over-wintering dahlias. I think it comes down to temperature combined with the necessity to store the bulbs for such a long time. We’ve had an unusually warm autumn. Years ago I found out I don’t have a cool enough place for overwintering dahlias or ranunculas. It takes a root cellar or a house cellar where there is no furnace or else inside the refrigerator. I took a look at my book on page 398 and if you had done what it said regarding “a cool place” I think you could have succeeded. I’m glad you pointed that out, however, since I will strengthen the language next time around by saying that the temperature for keeping bulbs needs to be in the high forties or low fifties, above freezing, similar to the temperature inside a lettuce crisper that does not freeze lettuce. If you cannot provide that then it would be better to buy new bulbs each year.

But for keeping them, here is the drill: Dig the bulbs in December or in cooler zones than yours, after they have been bitten by frost. (You dug them up a bit too soon.) Then let them dry out as described on page 398. (This was pretty specific.) Then knock off the earth and prepare them for storage. Some gardeners keep them whole, as I described how on page 398 in my book, and divide them in spring prior to planting in May. Here are some more ideas for storage: Try cutting them up prior to storage, cut off and discard any that are not perfect. Be ruthless! Also, each bulb must have at least one good eye. Dip the cut ends in fungicide and preserve them in vermiculite (not peat moss which is more drying) mixed with about a tablespoon of fungicide. Some gardeners find vermiculite works better than perlite. Others prefer dry sawdust. I think brown paper bags make good containers. Put each bulb into a separate one. Some gardeners store them in plastic bags left open but here it might cause rot. Then check every couple of months and throw away any rotted ones. If you refrigerate them, do so in a refrigerator dedicated to horticulture. (It’s not wise to put fungicide in a refrigerator in which food is stored.) I also think plastic can make the bulbs rot when under refrigeration, but not if there are a lot of holes in the bag.