I would suggest you wait until the Memorial Day weekend.
By that time there will be no threat of a frost. I don't aree with the temp for planting on the bag either. 50 degrees is still too cold to plant tubers. By waiting till the Mem Day weekend the soil temp will also be in the mid 60's, which is better.
DB

Uh-oh, so I'm doomed? I potted up a bunch this week, in gallon nursery pots, some saved from last year, some new. It's 80 today, may get down to 32 Friday night. Should I surround them w/ bubblewrap or bring them in the garage?

The garage wouldn't be a bad idea. Throw a sheet or something over them for extra insulation until your cool spell passes. I hate waiting for the soil to warm up, but DB gave you sound advice.

NewYorkRita,

Since you have no way of checking the soil temperature to make sure it's 60-65 degrees, the rule of thumb used by many colder northern growers is to plant the dahlia tubers when the lilac bushes are in full bloom.

That's a nice rule of thumb! If the lilacs are blooming the soil is warm enough? I've started most of mine in pots to get earlier bloom, but I will proably have later impulse purchases.

I moved all of the newly planted tubers into the garage, may wait another day or two to put them out. The 2 dahliettas that were the centerpieces of my recent container plantings are toast-I should have known better-oh well, they were beautiful, while they lasted! Linda, who is hoping for warmer weather...

I have pictures of my lilacs blooming in May... covered in snow. But I'm not a pessimist! My tubers are outside now in a portable greenhouse - they survived a recent freeze by hiding out in the garage - and my seeds starts are in the basement under lights. They have one set of true leaves. Does that mean I started them too late?

Peacelovebarbies- one set of true leaves is just about right for seedling babies right now. If they're in flats you can transplant them into 4" pots now to give them room to grow. They'll be a good 1-2' high by planting out time in May.

Plantlady2 - thank you so much! I will try to do that this afternoon. I'm getting the impression that 'room to grow' is more important than I thought. We're having some real nice weather right now so they are outside in a portable greenhouse. Thanks again for your advice!

Hi Rita-

I am 5o miles north of the city (NY that is) and I have always planted my dinnerplate dahlias on or about the second week of May without problem.

What I was told was you didn't want to plant them and have the sprouts clear ground and get exposed to frost.

Your gonna love "em.

Anyone know when is good for zone 4? I usually plant everything out by the 15th of May which is the last frost date. is this too early? I just received a box of bulbs.

Midnightgirl - are you sure May 15 is your last frost date? I'm zone 5 but usually we don't count on frost being out of the picture till the end of May, when we plant non-hardy annuals.
http://www.avant-gardening.com/zone.htm

PS on the lilacs, mine are in full bloom the first week of May now and we are getting night time temps in the low 40's. I think they are early - they also aren't as heavy as previous years. Lots of things look a little odd this year - all those warm weeks during the winter and then the hard freezes and snow in April.

I finially planted them and the last of my summer bulbs and tubers this past Wednesday. I figgure it was finially late enough. I think they are going to look really great with some glads placed between and some cannas planted behind them.