Rita, you must be so disgusted after your failures but I
know there's a solution. Please don't give up on these beautiful flowers yet! ( Even though I gave up on roses because of chronic blackspot and deer nibbling
.)
From reading above, it sounds like you need to control slugs, for sure. They will mercilessly mow down a tender young dahlia shoot in a New York Minute.
If they're rotting, you might be planting too early in too wet and too cool soil. They need no water until the tubers sprout a few inches above ground and the tubers develop feeder roots to actually absorb the water either we, or Mother Nature, provides them. Otherwise, it's like plunking a potato in a cold, wet muck and expecting it to stay nice and healthy.
I really encourage you to look at your soil drainage, slug control, and planting time to assure that your tubers are going into well-drained soil of at least 50ยบ. I've rotted more tubers than Doan's has pills over the years by planting too early in our notorious cold, wet NW springs but have finally learned to either pot them up and easily transplant later when the gardens are warmed up, or to just flat out wait til mid-May or even late May to plant outdoors.
I don't have a huge amount of really large ones, but if you're willing to try again, I'll gladly send you a box of free medium- medium/large tubers to try as well. Just tell me what colors you like. One of these times, you've got to be successful and then all your dahlia woes will be in the distant past. Maybe not all of them, but there's nothing like a little success to spur one on to greater things. They really are one of the most fabulous, long-blooming gems in the garden.
One of my favorite dahlia websites is in your neck of the woods. Their 'Learning Center' has good photos and tips that may be of help too. Don't give up!
http://www.midislanddahlia.com...
