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Dahlias & Gladiolas in pots

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  • Apr 14th, 2020 4:10 pm
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[OP]
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Feb 4, 2010
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Dahlias & Gladiolas in pots

I have dahlia and gladiola bulbs - I'm thinking of growing them in pots because I know I'm going to have trouble finding them in falls to dig up. Has anyone here done this? Were you successful?

I've also read using soil with polymer crystals helps with container plants but all the brand names are in the US - does anyone know what brand has them here?
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Mar 22, 2017
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West GTA
hierophant wrote: I have dahlia and gladiola bulbs - I'm thinking of growing them in pots because I know I'm going to have trouble finding them in falls to dig up. Has anyone here done this? Were you successful?

I've also read using soil with polymer crystals helps with container plants but all the brand names are in the US - does anyone know what brand has them here?
Miracle Gro Moisture Control Potting Mix has polyacrylamide in it. If you plan on using a fair bit, can also buy the crystals separately (use them sparingly!). Don't use the crystals on any soil you plan on growing stuff in, over a few years it degrades into acrylamide which is not great to eat, inhale, etc.

EDIT: actually, it doesn't have the crystals! It has 'aquacoir', which is different, natural, and probably doesn't work quite as well.
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Aug 30, 2011
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I haven't had a lot of luck growing the larger dahlias in planter boxes... they seem to do better for me in the ground. But the shorter and dwarf ones would be fine. Perhaps because I use a soil-less mix in pots and planters, which isn't as firm a base for the tubers to take hold? I did stake them, but they just seemed unhappier in pots, lol.
[OP]
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OttawaGardener wrote: I haven't had a lot of luck growing the larger dahlias in planter boxes... they seem to do better for me in the ground. But the shorter and dwarf ones would be fine. Perhaps because I use a soil-less mix in pots and planters, which isn't as firm a base for the tubers to take hold? I did stake them, but they just seemed unhappier in pots, lol.
Thanks. This is the kind of info I was looking. I did not think of the height issue...I don't think these are the dwarf kind...hmm. Perhaps I'll try with one or two deep pots. Or I could start off in the pots and if it's not going well then transplant to the ground with the rootball intact as much as possible?
Last edited by hierophant on Apr 9th, 2020 11:06 am, edited 1 time in total.
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May 28, 2012
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Saskatoon
I grow dahlias. Stored over the winter and planted into small pots around this time of year. Grow under lights in basement, harden them off a week before planting out. Dahlias do best in the ground but I always grow a few in pots. I have a couple of huge oak barrel planters on the deck and I plant one in each (along with other smaller plants). They get huge and you need to stake them well because the hollow stems means any significant wind will topple them. They like a loose, rich soil.

I've grown gladiolas in the past but they are a bit more finicky for me so not on my annual grow list.
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Apr 4, 2010
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I grew both last year in large pots (20-30 litre). We grow Dahlias mixed with other plants in planters. You have to deadhead and groom to keep them lower - which is what we wanted. I found the flower heads are heavy and both spill/flow over the edge of the pot and sit at a mid level. We add low level growth, like Coleus, and something taller. It looks good. Dahlias, when they are deadheaded, pump out the flowers.

Glads - I planted ~ 30 bulbs in one planter. We didn't get a ton flowers, maybe ~25-35% bloomed. They were planted a bit late, so might be the issue. The foliage was awesome though. I think I would do it again just to get the foliage, mixed with something that is shorter and flowers better.
[OP]
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Thanks everyone! When is a good time to pot them? Can I start now indoor or wait until last frost?

fotoapparat wrote: I grew both last year in large pots (20-30 litre). We grow Dahlias mixed with other plants in planters. You have to deadhead and groom to keep them lower - which is what we wanted. I found the flower heads are heavy and both spill/flow over the edge of the pot and sit at a mid level. We add low level growth, like Coleus, and something taller. It looks good. Dahlias, when they are deadheaded, pump out the flowers.

Glads - I planted ~ 30 bulbs in one planter. We didn't get a ton flowers, maybe ~25-35% bloomed. They were planted a bit late, so might be the issue. The foliage was awesome though. I think I would do it again just to get the foliage, mixed with something that is shorter and flowers better.
Just to clarify, you can "control" the height by deadheading?
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Apr 4, 2010
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Glads I wouldn't bother to start indoors. Dahlias, yes. Dahlias will do well if you have a sunny spot to start them, or grow lights. You get a bushier plant when you deadhead. Don't just cut the flower off, but cut back to a node. The plant will then grow side shoots, which will in turn flower. Cut the side shoot back to a lower node, and it will split again. You'll get a very bushy plant, that is shorter than if you just left it to grow on its own. Remember, depending on the variety, Dahlias can be tall (4-6) feet. But if you keep cutting back after flowering, you'll be on the short end of that.

Upside of cutting back, is you'll get more flowers.

Good luck. Best part about gardening is just giving it a go. If you have tubers, plant one now inside and plant another direct in the garden in May. See what happens. Then, next year, repeat what worked best.
[OP]
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Feb 4, 2010
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fotoapparat wrote: Glads I wouldn't bother to start indoors. Dahlias, yes. Dahlias will do well if you have a sunny spot to start them, or grow lights. You get a bushier plant when you deadhead. Don't just cut the flower off, but cut back to a node. The plant will then grow side shoots, which will in turn flower. Cut the side shoot back to a lower node, and it will split again. You'll get a very bushy plant, that is shorter than if you just left it to grow on its own. Remember, depending on the variety, Dahlias can be tall (4-6) feet. But if you keep cutting back after flowering, you'll be on the short end of that.

Upside of cutting back, is you'll get more flowers.

Good luck. Best part about gardening is just giving it a go. If you have tubers, plant one now inside and plant another direct in the garden in May. See what happens. Then, next year, repeat what worked best.
Thank you! This is awesome advice! What are your thoughts on planting one of the tubers in a pot but leaving it outside on a covered patio deck? Would it be protected enough from the frost?

Also if anyone has advice on how to repel chipmunks and squirrels from digging up my hanging and potted flowers I would greatly appreciate it.
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Feb 7, 2017
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hierophant wrote: Thank you! This is awesome advice! What are your thoughts on planting one of the tubers in a pot but leaving it outside on a covered patio deck? Would it be protected enough from the frost?

Also if anyone has advice on how to repel chipmunks and squirrels from digging up my hanging and potted flowers I would greatly appreciate it.
Know lots of folks who use chicken wire.

Especially so if planting seeds, bulbs or tubers ... otherwise you got cut your self a hole in the middle to get the seedling in

There are also lighter weight finer gauge solutions ... like netting. See your Big Box DIY Store, or Nursery for details.

Other possible deterrents ... water & cayenne pepper sprayed on regularly in a squirt bottle

Or you can use Wooden Skewers with the pointy side up ... can esp work on hanging plants if you got squirrels who like to jump onto / into the baskets.

As for planting tubers & Summer Bulbs ... we usually wait until things warm up a bit (including the soil) after the threat of frost is gone. Sometime in May
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Apr 4, 2010
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hierophant wrote: Thank you! This is awesome advice! What are your thoughts on planting one of the tubers in a pot but leaving it outside on a covered patio deck? Would it be protected enough from the frost?

Also if anyone has advice on how to repel chipmunks and squirrels from digging up my hanging and potted flowers I would greatly appreciate it.
I wouldn't leave it outside until it warmer. It is unlikely to grow much until it warms up and you're just risking squirrels/frost damage/rotting.

We have tons of squirrels in the area. I have some metal wire type baskets that I put over the freshly planted bulb. Once they start to have enough foliage, I just take the covers off and find the squirrels aren't a problem after that. You'll always loose a couple, but that's not worth making your pots ugly with covers.

I just got my tubers today. I'll plant them in about a week. I have a greenhouse, that I will move them out to on May 1st and I'll plant them out in the garden May 21/28.

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