What is the minimum amount of direct sun a cherry tomato plant needs on average?
Yes. Eight hours or more of direct sunlight .
Come December and January, I won't be able to give them 8 hours of direct sunlight, more like 5. They should have set fruit by then so hopefully that will be enough.
Usually "full sunlight" is defined as 6 or more hours of direct sunlight.
For many years, I had a garden right up against the east side of my parents' house. (The house faced directly west; I've checked it on Google Maps.) The tomatoes and cukes were planted just inches from the east wall. They had full sun all morning -- then no sun after noon. They did fine.
There's also what's called "bright shade." That means not direct sun, but still bright. For instance, the north side of my house, which never gets direct sun. Or in front of the house, where the daylilies bloom well despite receiving only 2 hours of direct sun at noon.
I was going to say I'd never grown tomatoes in "bright shade" -- but the first year I was here, somehow I had a volunteer cherry tomato show up on the north side of the house. It didn't do much, but it had several ripe fruit!
I grow cherry tomatoes that only get 4 hours of direct sun, from 10am-2pm everyday. They do just fine, I'm getting tomatoes like crazy. The plants are way overgrown too, so most of the actual tomatoes are hidden under leaves and probably don't get any sun. You don't need even close to 8 hours...
In a perfect world we could give every plant we grow the ideal conditions it needs. But the reality is that most of us have limited space and we cannot provide 8+ hours of sun for every plant we grow. We need to pick and choose and play favorites.
In my experience, cherry tomatoes do just fine in shadier conditions. 3-4 hours of direct sun should be enough to ripen a sizable crop. Cherry tomatoes can be so prolific that a somewhat reduced crop can be a blessing.
Smaller fruited tomatoes like 'Stupice' will also do just fine in 3-4 hours of direct sunlight. I find that it is only the tomatoes with fruits consistently larger than 3-4 oz. that will have difficulties in the shade. They never seem to produce much or to ripen.
HOWEVER, one thing you will encounter in shadier conditions is that it will take the tomatoes longer to ripen. You should add at least 2-3 weeks to the estimated DTM if you are growing in the shade.
Hope this helps,
I grow "wild" cherry tomatoes (currant-type really) in pots.
In the spring, full sun.
In the summer, I move them against the North side of the house in bright shade so they'll keep producing.
In the fall , they go back into full sun.
They overwinter there and I protect them from freezes.
Basically, if it's too hot during your summers to normally grow tomatoes, planting cherry tomatoes in bright shade will help you extend your growing season into the summer.