We also had some cold spells that may have affected them. You shouldn't plant annuals (tender annuals or perennials) in the Atlanta area before danger of frost is past (usually mid April is safe). If you do then you should cover them when there is a frost or freeze warning over night.
I agree, it's cold damage, AND over watering while it's cold in the soil, as mentioned above, annuals are the most tender of plants and have a short season, so they need warmer climes to grow, flower and set seeds, a lot to contend with all in a matter of months, best leave off planting more annuals till end of April unless you have a constant spell of warmer weather, cover these plants already in the soil by placing a layer of horticultural fleece over them at night, it just gives a bit of extra protection for when the colder nights are around, they will still be cooler evenings even with warmer day time temps.
When you do water, try not get the actual foliage wet just allow the water to reach the soil where it gets to the roots, the flowers and greenery are still not hardy enough for soaking with water.
I just realised you said you planted THESE MARIGOLDS LATE MARCH, THEREFORE, the plants must have been forced into flowering stage before you bought them, that's way too early to be planted outside, what you should have done was keep these plants indoors, in pots on trays, each DAYTIME, you place them outside and bring them back indoors, this is called hardening off, / acclimatising the plants to get used to there new environment and ajust to there new outdoor temp but it must be gradually done, not just instant from store to garden in March.
Hope all this helps you understand the plants needs and you can save the ones you already have, if not, a lesson well learned EH !!!!
They may have been bought in flower so usually are hardened off when delivered to the nursery or big stores, but a few chilly nights can put a zing in even the most hardened plants.
We had a small frost Tuesday morning (at least on my windshield) but even colder days a week or two earlier. Woodstock is in the next county up from where I live - it is perhaps 30 miles north so the temps should be close.
hcmcdole, I have 10 acres and believe me in different areas there can be a huge difference in temp when were coming out of winter frosts, Tree's can cause deep shade so even low winter sun is not able to warn up the soil for up to a month, but you just learn to work with it and after a few seasons, you learn and get to know your own plot. like you said earlier, the seasons are all mixed up, but we can only work with what we have at the time eh!!!!!.
Happy gardening season and enjoy the fruits of your labour.
Best Regards. WeeNel.
I hear you WeeNel. We get microclimates from the driveway to the backyard so we can get a hard frost in the front yard yet most plants under trees show hardly any damage. Really depends on how cold it actually gets. Right at freezing plants under trees or the deck might get by for a night or two but if it is in the teens (Deg F), then they will be mush as well.
Nurseries have to display their plants in full bloom or at least partial bloom here, else they won't sell. As a consumer I like to see a plant in bloom (if the bloom is what I am buying it for) because if the tag says orange and it blooms yellow, then I am stuck after planting it... Sure I could dig it up and take it back but if you had 200 bedding plants, that is a lot of effort.
Also I didn't say a word about the seasons being all mixed up. This is typical spring weather in Atlanta and the southeast USA. The supposedly safe date to plant tender plants here is April 15th but we got very close to freezing last night and while it will be a little warmer tonight without lots of wind gusts as it was yesterday, it will still be close to freezing. A lot of my larger plants are under my deck and that helps keep frost off this time of year but it doesn't keep the rays of the sun from burning tender foliage. That will toughen them up and in a few weeks you won't know the difference.
Understand what your saying about the dates for planting, Here in West of Scotland, the seed packets tell you planting dates are Feb - April for some Veg, but the soil is still un-workable, tooooo wet and cold and were into Mid April.
The seasonal temps have not been normal here and wider afield, and far from it.
My sister- in-law in her area (North Ontario) has seen late starts for spring this year and last 2 years, My friends in Australia are fighting drought and fires last few years, yes!!!!! they expect hot weather BUT nothing like the way the temps are going now, and we also hear a lot of the different States in USA are suffering wide fluctuations from NORMAL spring /summer temps, especially night temps, so I guess there are definitely different areas where they could usually go by planting dates BUT, now it's treated even more as just like guidelines, or by info / guidelines on the packet of seeds, NOW here, we gardeners have to learn to go by soil temp and pay more attention than ever to weather forecasts.
I can tell you that as a kid, (Long time ago) there were NO seeds planted until a kid was able to sit his bare behind on the soil and NOT flinch with the cold, so we were NOT in need of instruments or a man with a map telling us when to plant, OH and by the way, you still bought your seeds by the ounce / pinch / or bushel, no nice pictured fancy packets that give info that covers a country rather than an area, Who said Gardening was a nice laid back, genteel way to pass your days EH !!!!!.
Hope you have a great gardening season once everything settles down weather wise and you can enjoy the fruits of all your hard work.