I'm really not sure if it matters all that much or not as to where you
would get the seeds. I'd look more at what type of tomato I'm trying to
grow for the area I live. I find that some tomatoes do much better in
my garden than others and I start them all from seed indoors six to
eight weeks before I set them out in the garden. I also amend my soil
with a slow release granular fertilizer about two weeks before planting.
Then I push two tomato spikes into the soil for each plant at time of
planting. One tomato that works real well for me here in central
Pennsylvania year after year is Jet Star. I water my plants using city
water which I'm sure is full of chemicals but I never tested the ph of
the water. I give each plant two gallons a week if we don't get rain.
I also plant them very deep when I set them in the garden. Just about
2/3s of the plant or more in the soil. They will develop roots all
along the stem that makes for a good strong root system. I also stake
my plants for support and prune them to one or two main stems. Welcome
to the group, glad you could join us

Happy Gardening ............ Rich from PA