Seed packets of dahlia seeds are sold on some seed stands in stores and mail order. They are seeds of very small, bedding type dahlias that are nothing like the large plants sold as tubers. I would equate them to petunias or zinnias. Dahlias do not breed true from seeds and even these low bedding types have lots of variability. Dahlia breeders grow seeds from named varieties with the expectation that 90% of the resulting seedlings will not be kept to grow again. Dahlias grow true to type from tubers, and that is one of their great advantages. A really nice dahlia can be grown year after year from the tubers. The same applies to potatoes. They can be grown from seeds but the resulting potatoes are very inferior. Good potatoes come from good seed potatoes.

I tried stargazer dahlia's last year and was very pleased with the results. I did nothing special at all with regards to care or planting. I had one very beautiful cactus like flower with mauve petals with pink towards the center. I had another which was a single layer of flower that was yellow with pink around the edges. The only problem I had was with two which I put in the same pot with a few glads. The dahlia's didn't flower but produced big healthy tubers which I carefully excavated and saved. Some of my tubers went mouldy in storage but a few are good and one is sprouting already. For me the advantage of seed is that I don't have to spend a lot of money for tubers before I learn to store them over the winter.

I've repeatedly grown Bishops children from purchased seed and been extremely pleased with the results. It was pretty easy. I start them early indoors with some bottom heat (my previous house had a gas stove with pilot lights that was great for starting warm season plants - had to get a grow mat once I left there). I've also started them with the "damp paper towel in a baggie method" to sprout (again warm place) then planted. As in starting all seeds indoors, be sure to get sterile seed mix (or sterilize what you're using) so you don't get damping off. I like to start them early as they'll bloom sooner.