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Be careful with dahlias; they are highly addictive. Proof of that can be found in my portable greenhouse in the backyard which is nearly overflowing with potted up dahlias. I suspect I’ll have about 100 in my garden when it’s all said and done.
If you haven’t grown dahlias, rest assured, they are nice in small groups as they are by the dozens, and although I spend a lot of time fussing around with them, they are not difficult to grow.
I plant them in two ways: The “extra” way and the easy way.
THE ‘EXTRA’ WAY
By my way of thinking, the “extra” way of dahlia planting has three advantages:
- You get blooms earlier, often a few weeks before you would normally.
- They are easier to space properly as you are dealing with plants, not tubers.
- They give you something to fuss over while you’re waiting for gardening season to start.
But there are disadvantages, including the added cost of potting mix and possibly plastic pots (although I reuse pots from plants e purchased), and a bit of time spent caring for them.
In this method, you pot up tubers ahead of time and get them growing before planting them in the ground. I usually start potting up tubers about a month before my last average frost date (here in zone 5 Wisconsin that translates to potting in early to mid-April based on a mid-May last frost date).
Use regular potting mix (it’s best not to use mix with fertilizer mixed in) in a gallon-size nursery pot. Very small tubers can go in smaller pots. Put a few inches of potting mix in the bottom of the pot, then lay the tuber in on its side. (If it’s too big to fit that way, you can angle it slightly.) Cover the tuber with another 3 inches of soil. Just moisten the soil and then bring the pots to a warm spot.
At this point all they need is warm to sprout, not light, so I just stack them up in big tubs in the house.
Tubers sprout at different times, so after a few days, start checking for shoots emerging from the soil. This is when they need light. If you move them outside at this point you’ll never have to worry about hardening then off, so it’s best to get them outside into the sun.
Dahlias are pretty easy to grow but they are fussy about temperature. You really don’t want the out in less than 50 degrees at this point, but often a protected spot with bright sun will be warmer so you can move them there. Bring them in at night if need be. Or you can use a popup greenhouse like I do. Whatever you do, don’t skimp on the light.
At this point you also want to start regular watering. They don’t need to be drenched, just not dry.
It’s safe to plant them in the garden (or their final container) when the soil temperature is 60 degrees. You can use this method at any time, and you may want to, especially if you want to keep a close eye on a tuber, regardless of how close you are to the safe time to plant out. However, the closer you are to the safe planting-out date, the less advantage you’ll realize as far as early blooms by using this method.
THE EASY WAY
If that all sounded like a lot, the good news is that there’s a much easier way. You can plant your tubers directly in the ground when it’s time and skip all that fussing. You’ll have to mark them so you remember where you planted them and they’ll bloom slightly later than those you started earlier, but they’ll still grow beautifully.
You want to plant them in full or at least part sun about three inches deep by laying the tuber on its side.
Wasn’t that easy?
Regardless of how you plant, there are a few tips that will help you grow beautiful dahlias.
- Dahlias appreciate relatively rich, good-draining soil, but you don’t need to go to extremes to achieve either. I have pretty good soil that’s been amended with compost over the years, but I mix in a bit of a balanced organic fertilizer (something like Espoma Plant-Tone) before planting.
- The two rules for planting are warm soil that’s not soaking wet. A 60-degree soil temperature is good (honestly, feeling it with your hand is usually a pretty good way to judge) and you don’t want to plant if it’s been raining for days. Dahlia tubers don’t appreciated cold, wet soil.
- Stake right away. I speak from experience here. You might think you’re going to get lucky and your dahlias won’t fall over, and for awhile they will appear to defy physics, but fall they will. If you stake when you plant it will never be an issue. I use a variety of staking methods, but generally speaking, a study single stake that you can tie the growing dahlia to with soft twine, will work. For planting in a straight line, I use a Florida weave method.
- Pinch out the growing tip when there are about three or four sets of leaves (or when it just get too tall). Just pinch out the stem right above a set of leaves. This will encourage branching and you’ll get more flowers.
- Fertilize occasionally during the growing season. I use a mild organic liquid fertilizer with less nitrogen (the “N” in the NPK numbers on fertilizer) than potassium or phosphorus.
- Deadhead or cut flowers often. Cutting flowers will lead to more blooms, but if you choose to leave them on the plant to enjoy (and who wouldn’t want that beauty there), deadhead spent blooms by cutting the flower stem back to where it intersects another stem.
- When you receive tubers in the mail, they’ll probably be packed in peat moss in a bag. Open the bags and store them somewhere cool and dark, like a basement, until it’s time to plant them. They won’t look like much, but at the top of each tuber (the neck) there are little buds called eyes. Sometimes you’ll see them and sometimes they might even have sprouted a little, but even if you can’t see them, they are there and this is where the plant will sprout from.
If some of that sounds familiar to you, that’s for good reason. A lot of the care that dahlias appreciated is the same as that for tomatoes. In fact, if you treat your dahlias like you treat your tomatoes, odds are you’ll be in good shape.
So how do choose dahlia varieties? Since most varieties require the same care, it comes down to your personal preferences, although the one thing you should pay close attention to is the height. Obviously, the taller the dahlia, the more extensive and important the staking needs to be.
Here are some of the varieties I’ll be growing this year, almost all of which are new to me:
I’m very excited about this unusual variety with skinny, almost black petals. Dark dahlias are such an amazing contrast in the garden and in a vase. And since it only grows to 26 to 30 inches tall this is one variety you might be able to skip staking if you plant it in a not-too-windy area.
This is such a happy flower and you’ll also make the pollinators in your garden happy too. Bees and butterflies go nuts for these single-type dahlias. This is another short one, making it great for the front of the garden where you can sit nearby and watch the pollinator action.
This is probably what most people think of when they picture a dahlia. It’s huge, fluffy and a gorgeous shade of pink. One flower will make a bouquet.
This flower looks like a fire: reds, pinks, yellows and oranges with deeply cut petals that make it look like the best kind of crazy pom pons.
This pinky bicolor is full of flowers and, at 24 inches tall, perfect for use in containers. Just stunning color on this one.
This semi-cactus variety has such amazing texture and is so unusual looking. It would be amazing in a bouquet of hot-colored flowers.
Don’t let growing dahlias intimidate you: Those big, bold flowers are baked into that little potato-looking tuber you get in the mail. All you need to do is give them the right conditions, no matter which way you go about it.
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