Very important! They'll fall over in a wind & the stalk will either break or it will pull the plant out of the ground.
Pound the stake in when you plant so you can see where it's going & you won't hit the tuber. Tie about every
1 1/2 feet.
If they're dwarf or border plants you don't have to stake.

Thank you for the info. also how far should the stake go into the ground?

Thump it in so it doesn't wobble when you try to push it back & forth. Walt does ours a good 6-8". We use the green metal fence posts.

Don´t stake, crate the dahlia. With 4 stakes and wire create a crate, that keeps the branches between the the crate allowing only the foliage and the blooms to come out while maintaining the plant confined and bushy. Besides, with the wire if branches come out you have somewhere to attatch them to.

If one has a lot of dahlias, that's a lot of stakes Raul. And how would one crate/cage a seven or eight footer?

Inverted tomato cages work well too (on the usual 4 footers.)

Here is a link that might be useful: Inverted Tomato cage

It´s easy Poochela, because we don´t have them handy No-stakes and Tomato cages easily available to create the stakes I purchase a beam and have it cut into 1/2" x 1/2" squares.

Mexican ingenuity at it´s best.

Ah, ingenuity. Glad it works for you, Raul. Aren't the beams more expensive, or not, when all the sawing is done? You have to use what's available to you, that's for sure.

Just for fun, what was your high temperature today, give or take a degree?

Thanks everyone for the advice and I think I going to try single stake and the tomato page and see what works best for me.