Back in the day when we were all hanging out on Homegrown Goodness, I lamented the difficulty we have been having getting carrots to germinate in any kind of timely manner, and speculated as to whether we might get better germination if the seeds were bigger.
So last fall I sifted our seeds into a larger seeded group and smaller seeded group. They were planted on the 18th - nine days ago now, and began to appear on about day six. This is astoundingly fast and good germination in general, and I attribute it to the extremely unseasonable warm weather we have been having. So at least part of our problem, I would deduce, is that we have been insisting on planting them too early. As to the differences from seed size: YES! The large seeded section was clearly up the earliest, by a couple of days, and with much more consistency than the others.
I am, however, a bit perplexed by some of the results. We planted one section each of the larger and smaller seeds saved from carrots grown by us last year, some of which would be offspring of other saved carrots etc. The other two sections planted were Amsterdam Maxi and Flakkee (Autumn King). Flakkee, being a large, robust carrot, drew the outside position where there is the most competition from weeds. It was well-cleared before we planted.
Logically, the Amsterdam Maxi and the Flakkee should have been a mix of larger and smaller seeds since I presume the seed sellers don't sort them by size the way we did. So I would expect them to have come up spottily but at the same time in comparison to the large seeded from their own large seeds within the mix. They did not. If anything, they are trailing the small seeded home-grown batch. The seed is a couple of years old at this point, but it's certainly germinating and carrot seed seems to last well for beyond the age they are in my experience so I don't think age would be the reason. I suppose that our seeds are just that much more adapted to our soil after even one generation. (Most of the carrots saved for seed last year were from named varieties with just a few grown from a previous batch of our own seed thrown in.)
Now we will see how these carrots actually do as carrots; hopefully they are not all wild carrot crosses or something dire like that. Don't think so. I can never eliminate those crosses completely but they seem to be down to a dull roar.