Adatt,

As a rule of thumb, I would say that zinnias bloom in six to eight weeks. Day length can affect that, with long days allowing later blooming, and shorter days (or longer nights -- it is a photoperiodism thing) tending to accelerate blooming. From the standpoint of growing impressively big blooms, it is actually to your advantage if the zinnia isn't too quick to bloom, and takes time to develop a big strong plant first.

If you pinch out the center bloom when it is a tiny bud, you will encourage side branching, delay blooming, and get more but somewhat smaller flowers. It may be better to pinch the plant before the bud forms, but I haven't experimented with that because, as an amateur zinnia breeder, I am always impatient to see what the first flower will look like. If it doesn't qualify as a breeder, I may discard the plant altogether at that point to make room for another zinnia plant.

ZM

From your pictures, it appears your zinnia isn't growing in very good soil and even is standing in water and looks stressed....notice how the leaves are curling down in the last picture.
Frankly I don't give it much hope....

Linda is correct. You cannot dig soil from your garden and use it in a container...and be happy with the results. Most of the time, even the best garden 'dirt' turns into something pretty ugly within the confines of a pot. The pictures in your blog illustrate that perfectly. :-(

A good container medium needs to provide plenty of oxygen at the roots. Thus, such a mix should be porous, well aerated, and very fast draining.

Your zinnia is wilting because it cannot develop a root system in that mucky environment. It's a vicious circle: it wilts because the soil is chronically soggy but then you water it some more because it's wilting! I fear that this zinnia will not be able to develop properly because of a lack of roots.

In this situation, I doubt that even cutting back on the watering will help. Without the rapidly developing root system that most seedlings exhibit, your poor little zinnia is bound to wilt at any time.

I don't know what you may have available to you in the way of container mixes, so perhaps your best bet is to sow your seeds directly outside in the garden.