Many seedlings are small and not vigorous. This is often due to hybrids their genes mix poorly or they are not well adapted to the area. Many grapes are not vigorous in Florida heat. Others get disease. But my better ones are a huge plant after one year. Due to lack of winter some don't go dormat.
I tried all kinds of varieties and seeds. Most got disease or didn't do well until I got these zehnder seeds. Kyoho comes from Missouri native aestavalis (some Asian grapes have this) lubrisca, vinifers. Not really adapted to the south. I grow a huge amount of seeds (20-30 at a time) only a small number make it. With native grapes not hybrids of course all of them will be adapted though some seeds might not come up or plants get eaten by an animal etc.
There's virtually no winter here in south Florida. I have to refrigerate seeds to get enough cold on them to germinate. I think my cab zehn seeds didn't get enough cold most or all haven't come up I'm not sure. I guess I've been selectively breeding stuff that germinated with minimal winters as grape seeds need 3 months of cold before germinating.
The stuff that came up now if it freezes I'll have to protect it but it might not even freeze. And they are so tough they will keep growing through 33 degree temps generally. This is true of basically all native American grapes. European vinifers gets leaf damage in the 40s. Hybrids are in between but closer to the American side. My stuff seems to resist cold pretty well.
You have cold sensitive stuff like shuttleworthii it's mainly due to early blooming and can get damaged by a late freeze but the leaves themselves generally not damaged until it hits freezing.
Our lows are in the 50s or 60s now.
Some tropical ones or vinifera will go dormant with practically no winter. It figures out it's winter without a freeze. But the seedlings germinating now won't do that . They will only go dormant or die if it freezes.