Just about any media will do: slightly moist is important. If it's too wet, seeds go mouldy or drown and smother. If it's too dry, they wizen up and die of lack of water. Slightly moist will feel slightly cool in your open hand, but will not drip when squeezed hard. After that, any container will do, a small jar with a lid and about half full so there is air, a plastic baggie, again half full for air, a plastic tub with a lid...anything at all. Once every few weeks, check that it's still slightly damp and open the top for fresh air for a minute or two. I've used damp sand, damp peat moss, damp soil, damp compost and used tea bags. All are good, just be sure they are only slightly damp and check on the seeds from time to time. Assuming it is a species where the package of seed calls for stratification in cold conditions, then that is what they need. If you name the species I can look it up for you and post the recommendations for stratification. I have only grown the species around here myself, but would be happy to look up the requirements for something else for you. I have a copy of the seeds of woody plants manual.

Dahlias grow the very best when the soil temp. is constantly 60*-- no 2 ways about it! If they are already growing & you put them out they might just sit there stunted until the temp. gets up to where they need it to be to grow- or the tuber will rot & not have enough feeder roots growing yet to sustain the plant- then you've got a dead plant. Also- dahlias & tomatoes are related-- so there you go- what's good for one is good for the other! Your dahlias grow all summer long & as the temp gradually gets cooler, they keep going until frost- yes, it's colder than 60* but they've had all summer to put on semi-hardy stems & the fall to get used to the colder temps. The stems in spring are tender new growth & way more susceptible to frost than the woody thick stems that have grown all summer long. Why do Home Depot & all those nurseries have tender plants out now?? When they frost & die you have to go back to the store & buy MORE, of course! Stands to reason- if they can sell you the same plants a few times over they're going to! Most savvy gardeners don't fall for their tactics & don't purchase tender plants until they can stand up to the local weather.

My first seed starting attempts were with Jiffy Mix and later, with peat pots. I never had good results AT ALL. (the peat pots dry out in no time and before you know it your seedlings are dead) For a long time I used just a high quality potting mix, and it worked pretty well. But a couple of years ago I decided to experiment with Gardeners Supply Seed Starting mix. I like it very much and I do believe I have a higher rate of germination with it. I also keep a bag of vermiculite on hand for dusting over fine seeds. It holds in the moisture and the seedlings can come up through it very easily. I really think that for most beginners, it's more about technique than it is about the medium. It certainly was for me. Read the seed packet carefully. If it says the seeds need light, be sure they have it This may mean you just press the seeds into the soil and don't cover. If it says dark, put the pots in the dark, keeping close watch so you move them into light as soon as they begin to come up. Also, pay attention to the germination temperatures that are stated. They are very important. It's always a good idea to google the plant you are growing and learn all you can before you begin. And finally, moisture control is crucial. Moisten your medium well before you put it in pots. Sow seeds and give just enough water to settle them. Let them drain a few minutes and then put them in an airtight location. I use Rubbermaid clear storage crates for a whole flat. If you are only starting a pot or two, you can put them in a ziplock bag. This will keep the atmosphere moist and help the plants come up more quickly and more uniformly.

Sounds like you have pot tubers from Holland, sold by general catalog plant companies and big box stores ... A confusing mess with what looks like a stalk with lots of tubers (often broken) hanging off it? Sound familiar? The great thing about these things is that there are normally many potential eyes ready to sprout up if the main sprouts are broken off. The not-so-great thing about holland' pot tubers is that they are very difficult for the new grower to divide or take cuttings from, as the clump is often a mess. It might be advisable to rein back on your learning curve, and save cuttings for next year's project. But if your spirit moves you to be adventuresome, go for it! Just be prepared for failures while learning... All part of the learning curve. "Get a slice of the tuber." Not sure why you'd want to do that. If you cut a sprout out of the tuber, you have effectively ended the sprouting capability in that area. If you cut under a leaf set and above the tuber by an eighth of an inch, three or four new sprouts will develop around the sprout stub within the week. You can pot up the 2-5 inch cutting, water well and cover tightly with a Baggie... The sprout should root well in a couple weeks and begin top growth.