All seeds lose viability over time, but I save my crackerjack marigold seeds for a couple of years and they do fine. Some flowers like marigolds and wildflowers don’t need very rich soil. I would not fertilize unless nothing grows there at all. I would still prep the soil with compost and make sure that drainage is good. If I fertilize, which I really don’t need to do since I do soil testing, it will be side dressings after the true leaves have come out. I don’t like to start flowers in pots. They do grow, but since I do compost, they are not easy to transplant.
Marigolds don’t grow in cold and wet conditions. They germinate poorly, dampen off, and get mildew and fungal diseases, so I would wait to plant until the weather is warm at least 68 degrees and you are not expecting prolonged periods of rain. However, I do like to plant seeds right before a storm comes, because, seeds germinate better when you get a good storm with light to moderate (not flooding) rain continuously, for a day or two. If it is not going to rain and you want to plant. Make sure you wet the soil well first, I use a sprinkler and run it for about 20 minutes which is enough time for my soil to be wet at least 4 inches deep.
I lightly scratch the prepared wet soil with a bow rake so the crust is broken. Also, I am not a row planter, except for corn. I mix the seed with some dry potting mix. You can use sand, but I don’t have any so I use potting mix. About 1 cup of potting mix will cover about 50 sq ft. It is mainly so I don’t get clumps of seed all in one place. I will have anywhere from 200-500 seeds.
I sprinkle the seeds over the area. and I do not cover the seeds. Birds here are not the songbird type. They are mostly fruit and seed eaters. I either put down a lot of seed or I have to rig a fence with bird netting over the seedbed. Birds are smart, they can get tomatoes by going under the netting and shade cloth, so I usually find it easier to put down more seed and run the sprinkler on a timer at intervals for brief periods. Don’t let the birds see you planting seeds! Do it at dusk after the birds have gone back to roost. BTW grass seed = bird food here. Most of us plant grass by plugs.
Another thing you can do is cover the ground after planting with 1 layer of newspaper and wet the newspaper to keep it from flying away. Water over the paper and water to keep the paper or soil slightly moist, but not soggy. You don’t want the seeds to dry out. You will have to check in about a week to see if the seeds are germinating and peel off the paper once the seedlings start to come up. Seeds start better with light.
If you need fertilizer, apply it after the true leaves have emerged. The seeds have enough fertilizer to get the plants through the first couple of weeks. Too much fertilizer (especially nitrogen) and inhibit germination and make dampening off more of a problem.
For me, I do water every day for about 10 minutes with a sprinkler or by hand. (Unless it has been raining all day and night for weeks). If anyone wants to plant marigold seeds then can follow this instruction for planting marigold seeds.