New Dahlia dame - I can use some help

I'm a complete newbie. Friends gave me tubers last week. I understandthey should be planted horizontally. My questions:
1) I'm in Portland, is it too late to plant? 2)Do they need special soil? 3)How soon and what kind of support?
Thanks!
Bea in Oregon

I've planted dahlias in mid-late June in the past. I just accept the fact that they will bloom late. I don't worry about them being a little late since I usually have blooms until mid-November. Plus the fact that the plant is producing more tubers for next year. They should be planted horizontally with any sprout/eye facing up, although they will always find their way up no matter how they are planted. I've seen dahlias growing in about every soil type. The main thing is that they need good drainage. If your soil has a lot of clay, you can add compost, peat moss, sand, etc. to break up the clay. Clay doesn't drain well and there's a good chance that the tubers will rot if you get a lot of rain. I start staking when the plants are about 18" tall. I use 5' pieces of 1/2" EMT conduit from Home Depot. There are many other things you can use but I like the EMT for it's strength. Some of the taller plants with big blooms tend to get a little top heavy.

Thank you psudan! I had wondered about support. It is wonderful that inexpensive conduit will do the job.
Is there a way to know if my tubers can withstand the winter? The Portland area doesn't get winter temps much below 28-30 degrees. Just a few dips into the 20's. They are in a bed that is at the top of a rockery wall and in augmented clay soil. You are listed as living in Ohio. Do you keep yours in the ground?
Thanks again.

With the cold temps we get, I have to dig my tubers every year. If I didn't they would be mush by springtime. Even in a warmer climate I would dig and divide every year. The way some dahlia clumps grow, I would have a monstrosity of tubers even after one year of failing to divide. They would probably get so big that they would sap their own energy. All the nutrients would be eaten up by the tubers instead of going into the plant itself. Besides, dividing gives you more free plants.

The last time I bought the conduit at HD I think it was around $1.50 for a 5" section. They are cheaper than rebar and much sturdier than those flimsy green fiberglass garden stakes. And they can always be spray painted if you don't like the shiny finish. The 10' sections are just a bit more but a little awkward to get home and cut in half.

I'm excited. The first few dahlias have started to break the soil.
Thanks for the info psudan