When it comes to direct-seeding, I recommend looking for the following:
• Seedling vigor (I've noticed some breeds tend to get bigger faster in my unheated greenhouse; I think this is perhaps the most important trait for direct-seeded tomatoes)
• Ability to withstand sudden, and dramatic, temperature changes (as well as sudden changes in rainfall)
• Early breeds (early to flower; quick to set fruit; quick for fruit to grow to size; quick to ripen)
• Those that are able to sprout in colder temperatures than average (and in both wet and dry conditions). This is very important, because tomato plants can grow at colder temperatures than they tend to sprout (normally).
• Prolific breeds (early isn't all that nice if you only get a few fruit overall)
• Wind-tolerant breeds
I've had success direct-seeding my Galapagos Island tomato (S. cheesmanieae), even though I direct-seeded it kind of late. It's the earliest tomato I've grown to date. I'm glad to hear about Sweet Cherriette, though. I definitely want to get it.
I didn't direct-seed these, but this year, the following tomatoes sprouted earlier in the season (when it was cooler):
Black Vernissage, Palestinian, Porter, Sausage. Black Beauty and Nodak Early were the first two to sprout in a much less desirable seed-starting mix (everything took longer to sprout and grow in it).
The following had great seedling vigor:
Chris Ukrainian, Black Dragon, Black Vernissage (much better vigor pre-transplant), Coyote, Matt's Wild Cherry, Marion, and probably others.
Marion had excellent germination (not only rates, but the seeds popped up pretty much perfectly and neatly).
The first plant to flower (of those I grew from seed) was Coyote. Others got buds pretty quickly, too: Bloody Butcher, Moravsky Div, Marion, Black Dragon, and Red Robin.
Last year, the first to sprout were these:
Super Marmande and Large-barred Boar. Neither were early to fruit, though. Frosty F. House, Burpee Gloriana and a number of others sprouted soon after—both of those would probably be good candidates for direct-seeding. Frosty F. House is quite early, with a polite plant, and I like the taste.
In 2017, the first to sprout were these:
Amethyst Jewel, Evergreen, Good Old Fashioned Red, Menehune, North Dakota Earliana, Green Pear, Girl GIrl's Weird Thing, Napa Giant, and Oroma. I don't recommend any of those for direct-seeding, personally. Green Pear seems to make a decent volunteer, though.
Sweet Orange Cherry is an early one with good post-transplant vigor (after it gets a certain size, anyway). It's prolific, too. Seeds have historically taken a while to sprout, though. It does seem to sprout faster every year, though.
One thing you can do instead of direct-seeding the traditional way is to squish a fruit where you want it to volunteer the season before. That seems to work a lot of the time. You just have to remember what it was and where you squished it.
Matina was a favorite for earliness and vigor in 2016. It didn't fruit as well in 2017, with less water, but the vines were still rampant.
If Brandy Boy F1 is anything like the accidental cross of a stabilized Brandy Boy with something else, then it could be a really nice one for direct-seeding). I'm growing out at least eight F2s from the accidental cross, this year. They were all in the less-optimal seed-starting mix (so, they got a late start, but they're looking good).
Sausage might be a good one, if it's not too late. Ask me at the end of the season. I didn't direct-seed it, but I did transplant some seedlings with only cotyledons. I imagine if they do well, direct-seeded ones might do even better.
Chocolate Pear might be a decent one. It's early and reasonably prolific. Sasha's Altai, Mountain Princess, Nodak Early, New Yorker V, Manitoba and others might be good, too.
