No, no and no.

I start mine inside in potting soil. They get transplanted outside around Memorial Day into beds of amended soil.

In the past I've put those dinnerplate dahlias in the ground before the end of April. They get planted deep -- 4 to 6 inches down, if I recall correctly. They were no worse for being planted that early, but it did not hasten their growth much at all, as the soil temps are not warm enough to get them going.

On the other hand, if you start them outside too early, long rainy periods can turn the bulbs to mush, because they're still sitting dormant and, instead of using the water, they just sit in it. Not good.

So now I wait until Mother's Day to plant them. Being buried so deep, they will not be affected by transient frosts.

If you're borderline zone 4, I agree that you may want to start them indoors and plant them after Memorial Day.

Mad_Gallica's idea is good, and I would try that myself if I didn't somehow manage to kill just about any plant that crosses my threshold. This is why I winter sow (not dahlias, of course) instead of starting plants indoors. I absolutely suck at nurturing any plant that is inside the house. :-)

Jean, Hi there. I start my Dahlias inside around Apr. 1 and plant them out after Memorial Day.
KW

Ok my dear gardening friends......

I must have 30 dahia's.....if I pot them up......what kind of conditions do they need in the house.

Right now they are in my basement....60 degrees.

The house is 70 degrees....but I don't have sunny areas to put them.

Work your magic and guide me!
Also...any tricks with the soil you use?

Thanks for your help and support!

Jean

I probably have 30 dahlias also. Too many to plant up in pots. I just plant them outside in mid-May and they do great and start blooming in August. Last year was so mild they bloomed into November. You can plant them 2 weeks before last frost, because it takes about that long for the new growth to break out of the soil.