Hi,
It depends on whether or not the plant has perfect flowers. Perfect flowers means it has flowers with both male and female parts so the plant can produce seed regardless of whether there are pollinators about. Tomatoes have perfect flowers so there is no need to hand pollinate. If tomato flowers are not developing fruit, it is because of high/low temps or some other stress factor(this applies to other plants too.) So trying to hand pollinate will not help.
Other plants are out breeding meaning flowers have only male or female parts and the flowers must be pollinated by insects or the wind. These types of plants like squash, can benefit from hand pollination if pollinating insects do not seem to be around.
Marigolds produce seed quite easily and I'm going to assume have perfect flowers so hand pollination is not necessary. If you wish to do it though, you can. You just break off a flower and rub that flower against others. For marigold type flowers, no q-tips are necessary.
Hope this helps,
Remy

Hi, Remy! Thank you again! It just so happens, we found a marigold flower today that was spent (Petite Yellow). And we've already pulled out the seeds. Is it possible to germinate them immediately to check for viability? Or should we allow the seeds to dry for some time? :-) Thanks!!!!

Hi,
I don't know if they need a rest period before they will sprout or not. You can tell if they are good seed easily. Good seed will not bend easy. Bad marigold seed is very flimsy.
I am wondering though if you let the seed develop long enough on the plant. The whole bloom including the base should be dry before picking. So blooms that died recently, are not ready for picking. Does that make sense?
Remy

Hi, Remy. Umm... Thank you about the seed not bending tip!!!

As for whether we have left the bloom long enough on the plant to dry, gosh I'm not quite sure I understand. Actually, I was able to pull several of the seeds out of the bloom, right on the plant, when I was checking on it. Does this mean it is dry enough though?... The seeds are still drying indoors though.

Please clarify. Thank you so much, Remy!! Really appreciate it!!!

Hi again,
Being I would have to see the flower, it is hard to say. But since they came out easy, maybe. It isn't that they are drying in the dead flower, they are ripening.
When the flower is finished, the seeds are starting to develop. How long depends on the type of flower. For some it is very quick, 4 O'Clocks come to mind. Other seem to take forever to ripen.
When flowers like marigolds are finished, the seeds as you know ripen in the base of where the flower was. You have to wait for the base to dry up before taking the seeds out to ensure they have properly ripened.
So the whole process is sort of like a pregnancy. The flower blooming part is when the sex happens. Then the seed ripening time is like a baby developing. If you remove the seeds too soon, they haven't developed properly. It is like a premature birth.
The drying once you remove the seeds, is because there is a residual amount of moisture in them. If you store them before it is gone, you risk the chance of moisture collecting and causing mold which kills the seed.
Hope that makes sense,
Remy

Hi, Remy! We wouldn't have thought the seeds needed to ripen first. Ahhh... Thank you so much for the clarification. I think we've got it now. We have several more blossoms that appear to be drying up so will leave them on the plant as long as possible. :-) We appreciate all of your help and wonderful advice!!! :-)

We're so eager to start our mini flower gardens!

Glad I could help,
Remy

Hi all. I usually deadhead my marigolds until the fall then let them die on the plant. At some point after that, when the flower heads are nice and brown, I'll break a few off and break them open for the seed. Unless you want thousands of marigolds a few flower heads usually give me all the seed I need. I've even gone out in January and grabbed marigold seed (I don't usually clear my baskets and planters till the spring) and it grew.

Caryl

I'm wondering if there is an advantage to keeping marigold seeds in thier natural 'containers' to retain viability between seasons, i.e., is it better to flake off the dried flower petals and open the seed base to free the individual seeds or to keep the dried flower head intact to keep seeds in darkened storage?

to add to this I have a question.

Can you deadhead a flower too early? of the few marigolds I had, animals or bugs ate the heads before I could get to them. Could I have cut the heads off before they dried up and let the seeds ripen indoors in the flower? Or do I need to wait until the head turns brown?

I would wait until they turn brown and also turn down to face the ground.