I grow over 200 tall-growing dahlia plants each spring. The largest varieties, such as Citron De Cap, Lady Darlene which have grown as tall as 6-7 feet, are staked with only one stake. The stakes are approximately 6 feet tall and made of steel. You probably would not want to use a different stake for each stem. On a windy day, one stake could loosen in the ground and tilt, which would put strain on that particular stem, and that stem could very easily break off from the plant. Hope that this helps.
Paula

One stake per plant is fine- just tie them about every 12-18".

You can even support two with one stake if you give them enough room from other plants for air circulation. I do have a question though. If you have several stalks, will tying one stalk be adequate or do you corral all of the stalks and tie them to the stake?

Veryzer-

Plantlady, if you don't already know it, is an absolute doll. You might also consider an alternate method, which she explained to me in the thread below:

Here is a link that might be useful: alternate staking method

Second the motion that Plantlady is a doll; always helpful with her vast dahlia knowledge.

Monet you answered a question I had about two plants per one stake, something I am going to try this year in places. To answer yours: corral all the plants' branches with a gentle hug of a tie. Especially when laden with a heavy large, or many smaller blooms, those branches are very prone to break in a wind or wet weather. Best to give all limbs some support to prevent needless loss by breakage.

Some of the really robust growers get two stakes here, at distances apart where I can assure I'm not stabbing into tubers of a neighboring plant, but that can still anchor athe very large dahlia from blowing over in a rain/wind storm. Thankfully we don't get those very often. A 6 foot 1-2 inch bamboo pole has worked really well for some of the bigger plants here, or 5 ft steel fenceposts. Very secure if pounded in well and last a long time.

I'd welcome any helpful hints on growing two plants per one stake. I know I've seen it online in someone's garden: at the ADS or Colorado Dahlia Society site perhaps.

WOW-- you ladies are going to give me a swelled head! We grow the dahlias in the show gardens- aka- the Greenhouse Garden & the Sheep Pen Garden, 2 per stake. We use the 6' steel farm fence posts. Dig your hole- 4-6" deep, put in any ammendments you use- we use 10-20-20 fertilizer & peat soil from the bottom of the farm, pound the stake in the middle of the hole, plant the tubers with their neck end right up against the post-- one on either side, cover w/ about 1" of soil. When the plant starts to grow & push through the soil, just keep filling in the hole until you have a bit of a mound over the tuber. Tie the plants individually to the pole as they grow. Tie all the laterals of one plant together-- ie. go around each plant with one loop of twine, do a figure 8 tie around the post & tie at the back. Do this about every 12-18" We use Christmas Tree twine to tie up all the dahlias whether we do them at posts or in rows.