Because we can grow four seasons, but have the extreme of heat and freeze, we have annuals, both flowers and veggies, for winter and for summer, or for cool and warm seasons. It is hard to know quite how to handle that space wise. Cool season plants go in during September, and the timing is tricky. Get those snaps in too soon and that inevitable hot week mid September will fry them. On the other hand, get them in too late and they do not get up and going enough before fog so sit and sulk until mid February. Then in April when we get that first warm week of mid 80 weather and everyone starts walking around saying it's hot, all the cool season annuals turn brown and are done, all at once just like that, leaving big gaps to fill.
On the other hand, warm season annuals can go in as early as mid February and go until a hard freeze, sometimes as late as Christmas, but more typically later November. So there is a big overlap of time that both can be growing, or one has to come out mid stride to make room for the other.
My solution is first the self sowing winter annuals that start coming up anytime after it turns cold and grow green all season and bloom Feb-April, more or less. At our house those include California poppies, which of course are not poppies at all, poppies, especially the Flander's Fields poppies, larkspur, and nigella, or love-in-a-mist. There are also forget-me-nots, johnny-jump-ups and some others not as important. Alysum of course grows year round. Once the spring flowers go brown, the cosmos is already up and going and fills in nicely. Jerry especially likes having another orange to replace the California poppies. Zinnias are another summer annual that is happy to be planted early summer and easily pulled at any time. Zinnias are awfully stuffy flowers though. I got back and forth on those, red flowers to bring in the house, vs ugly. : )
As for bedding out plants, I am pretty much into either pots or just a few here and there. Jerry likes what we call Taco Bell flowers, the little white gold and orange single zinnias, so I tuck a few of those at the front of the borders. Those are summer flowers, and I think the only kind I get other than my impatiens, which I have discussed before. In the winter I vary between pansies, and Iceland poppies and snapdragons. Just a few for pots or a corner of a border.
Here is my all time favorite photo of my spring annuals