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How to Care for Dahlias

By Jessica Smith ; Updated September 21, 2017

When caring for dahlia flower bulbs, remember that they are heavy feeders that require a slow-release fertilizer. Take care of dahlias by keeping them out of the cold with tips from an experienced gardener in this free video on flower bulb gardening.


Hi, I'm Jessica Smith, with Bland's Nursery in West Jordan, Utah, and today, we're talking about how to take care of dahlias. Now, dahlias really do not need any specialized care than any other types of flowers. However, they're not cold hardy in the colder climates like where we're at, so you will have to lift the bulbs up before the ground freezes in the fall. Now, when to plant them in the Spring you need to either; if you're planting with the bare root tuber, and that's the little fat bulb part on the, the root itself is what it is, you're going to plant that about three weeks before your last frost. If you're going with a transplant, one that's already started for you at your local nursery, you need to wait until after your last frost. They don't like the cold. They can't take a frost, so they will actually freeze back for you. They'll probably usually restart from it, but you've already lost your top growth at that point. They do like to have an organic mixture mixed with your soil when planting; irregardless of which way you're planting. What you want to do is if you didn't recondition your soil in the fall, add it about two weeks before you're going to plant so that it can actually break down a little bit and settle. What you're going to do is if you're planting with the tuber itself you're going to plant it, you're going to plant it actually horizontally, and you're going to plant about three, four inches down below, or you take the tuber itself; your dwarf types are going to be smaller, as with the dinner plate dahlia it's going to be a larger bulb, and plant it about two times the depth of the length of that bulb. Put your tuber down in, or if you're planting with a pot just to soil level, and make sure you water it in. Now, dahlias don't like to dry out that much in between waterings, but you do need to let em' dry out some. Too much excessive moisture'll actually rot the bulb. Dahlias are also heavy feeders. What you want to do with a dahlia is you can put a slow-release fertilizer down in the hole when planting, and then also when they come and they begin to set their buds for the blooms in that. You want to go with something with a high phosphate level. This is your middle number on your fertilizers. Phosphate is what helps build the root system, and gives nice big flowers for ya' and will increase many of em'. Now actually, when you go to lift your bulb; well, this one's already been lifted out, you actually want to leave it down in the ground if possible to promote some new eyes on the bulb. And what you're going to do is cut about to where it's five to six inches, and you're going to leave this basically down in the ground. A light frost'll do this also for you, but you want to make sure your bulb is up before the ground freezes, and you want to leave em' down in the ground for about a week. And what that'll do is that'll pro produce new eyes off of the tuber itself. It'll just make it easier to help divide after you lift em'. After you lift the bulb, in about a week later you're going to kinda' want to get rid of your excess soil. You can see the nice little tuber right here. This is off a little dwarf dahlia right here, and we haven't again pushed the eyes because I just lifted this one. It was already, already growing. And what, what you'll do is you'll you'll want to get all this soil off. You can actually take a soft, put it under your garden hose and kind of wash it off. You do not want to rub on the bulb though. You're going to take off those eyes you just produced. You're going to put this bulb into a dry, cool location; not out in the sun, that'll shrivel it up, for about a week. At that point you can actually go ahead; divide your bulbs up, and what you'll want to do is store the bulbs or the tubers in vermiculi or peat my moss itself. You can dust em' with a fungicide at this time; the fungicide will just help prevent mildews and that, and store them in those peat moss or vermiculi, either in a perforated bag that has holes in it, or in a box, and put it in a dry, cool location; around forty five to fifty five degrees. You don't want em' to freeze again. And then just check em' periodically throughout the winter. Make sure they're not shriveled or damaged, or any mold. If they are, get rid of those because they're not going to be a viable bulb, and you don't want that that mildew to spread to other bulbs. Each year, you can just replant your tubers that you've saved from the last year, and just enjoy your your same dahlias year after year after year, and produce more.


About the Author


Jessica Smith owns and operates "Blands Nursery" in West Jordan, Utah. Smith has work with plants and flowers for 22 years, since 1986.