Dahlias forum→Dahlia plant heights

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Name: aka Annie
WA-rural 8a to (Zone 7b)
Sandsock
Oct 4, 2020 11:14 PM CST
I am so confused by the dahlia plant heights that different websites list. Swan Island often has a range of 3-5 feet. My soil seems to grow some terribly tall plants (8 foot lilies that were only supposed to be 6.) Do your grow on the taller end or shorter end? What often governs the height?
Indiana (Zone 5b)
Rabbit Keeper
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French_Peasant
Oct 9, 2020 7:30 AM CST
I went out and did a quick check on sizes; SI lists "Dad's Favorite" as a 4' variety, and mine is gloriously happy and towering over 6'. Daydreamer is listed as 4' and is as tall as I am at 5'6". Appleblossom, planted in another area, is probably right on its 4 1/2' mark, while Center Court, in the same area, also very happy and robust with tons of blooms, is probably a foot or more shy of its 5' mark (but not well staked) (also, in the SI 2020 catalog, on one page it says it will get 4 1/2 foot high, while on another page, it says 5', lol, so even the catalog doesn't know). So, based on my n=1 evidence, dahlia height is pretty much the Wild West, and much more of an art than a science. Hope that helps!

EDIT TO ADD: These are grown on a sandy loam soil heavily amended with compost, and fertilized with bone meal in the planting hole. They were watered lackadaisically, ie, watered once a week through our drought, or when I noticed they were drooping. These particular varieties were from SI.
[Last edited by French_Peasant - Oct 9, 2020 7:36 AM (+)]
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Name: Arlene
Southold, Long Island, NY (Zone 7a)
I was one of the first 300 contributors to the plant database! Tomato Heads Dahlias Houseplants Garden Ideas: Level 1 Photo Contest Winner: 2014
Celebrating Gardening: 2015 Plant Identifier Million Pollinator Garden Challenge
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pirl
Oct 10, 2020 2:27 PM CST
I feel the amount of sun a dahlia gets critical to getting the expected height. Even when in full sun, some will grow taller than what we see as the given height. Perhaps it's the nutrition that causes it.
Name: aka Annie
WA-rural 8a to (Zone 7b)
Sandsock
Oct 12, 2020 5:31 PM CST
Oh French Peasant, that is exactly the kind of soil I have! I wish all my tall flowers would give my corn some height...not sure why that seems to be one of the few things that stays short, but it does. I saw a youtuber that had about 2 foot tall dinnerplate dahlias and had serious dahlia envy...then I remembered that I would worry if they were supposed to be 4 feet.

Now I have to figure out how on earth to get dahlias to look nice with roses...I'm thinking I am going to either have to go from seed (worked out well this year) or Holland border dahlias.

I did order a bunch of American Dahlias from Pleasant Valley and I will trial them, may have to count on the bushes as good compost material if I can't really see the flowers.
Name: Top
Missouri (Zone 6a)
Peonies Dahlias Region: Missouri Seed Starter Zinnias Daylilies
Irises Hummingbirder
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Topdecker
Oct 13, 2020 2:47 PM CST
Doesn't pinching help reduce the height?
The return of perennials in the spring can feel like once again seeing an old friend
Name: Arlene
Southold, Long Island, NY (Zone 7a)
I was one of the first 300 contributors to the plant database! Tomato Heads Dahlias Houseplants Garden Ideas: Level 1 Photo Contest Winner: 2014
Celebrating Gardening: 2015 Plant Identifier Million Pollinator Garden Challenge
Image
pirl
Oct 13, 2020 2:57 PM CST
Pinching temporarily reduces height but is more effective at creating a bushier plant. They'll still grow tall 3.5' to 5' unless they're short dahlias.

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