I see you're fairly new to GardenWeb so Welcome! Regarding your questions, some seedlings will sprout and then not show any immediate signs of growth; what they're doing is developing roots.

You didn't say exactly how long the seedlings have been up or what kind of growing medium they're in. If you really feel they should be showing signs of growth at this stage, you could try giving them a very diluted liquid fertilizer (like one fourth the recommended amount). Most importantly, make sure you don't over water the seedlings! By far, more seedlings are killed by over watering than under watering.

Normally, the plants you've mentioned should begin blooming about 60 days after germination. Of course, it would depend on weather conditions etc. All the plants you've mentioned like at least 6 hours of full sun. Some sun lovers like even more sun, but might need regular watering in really hot weather.

Hope this is helpful, and I wish you the very best.

Art

Thanks for the suggestion.

I planted the seed indoor :
Morning Glory : since 1 Sept '13
Carnation and Zinnia : 12 Sept '13

So I'd better put them on direct sun?
But they're still so small and have fragile stems, I'm afraid their stems will be weaken/ wither, or easily blowed by wind..

Sorry if I misled you when I mentioned that your plants like full sun. What I meant was that after they have been hardened off and planted outside, they like full sun. Of course, you wouldn't want to move seedlings, grown inside, directly to full sun. By the way, if you have a small fan, directing a slight breeze on your seedlings will help their stems. Some folks use a timer to have the fan come on every few hours for a short time.

If you're unfamiliar with the hardening off process, there are many good articles on the web that explain that in detail.

Art

I planted some small petunia plants several years ago in the fall and expected them to bloom in the winter here in Northeast Florida. Nothing. They wanted a specific sustained outdoor temperature and light, then they burst into bloom in spring.
Each flower may need different temperature/light cycles based upon where they originated originally. Data sheets from seed developers tell the growers how to simulate the plants requirements to force some to bloom.
Another example, I am planting The new Sparkle Guara.
The data sheet says something very important:
"Flower timing:
--Sown in January for Spring production, will
flower naturally in early May to early June
dependent on temperature.
--Sown in July to early September for overwinter
production, will flower mid to late May of the
following year.
Point is regardless if I plant either time I will get blooms when the plants "knows" it is time genetically, about May :-)

That CAN be forced if you recreate the required conditions.

Some plants are not light/temperature sensitive; most are.

I personally like to look up each plant on the web to learn what to expect.

Some plants of the very same type, bloom at different times, life black eyed susans. I have some varieties that bloom in the spring, others summer and one oddly in the winter.
It is fun to learn about plants. DON'T get discouraged. The reason I love plants is because I am constantly learning. If one doesn't work for you, drop it and move on. There are many more to conquer.

yes, it's quite a dilemma for me.
If I plant them indoor for several days, it seems they become "leggy", their stems are stretched and very thin which causes them to be more fragile --> then when I move them outside most likely the wind will blow them easily...
I am thinking maybe seedlings are okay to be put outside, but covered with, you know, such as plastic bottle as "mini green house" so they'll be protected.

Btw I'll try your method of using fan,,thank you for the help ! :)

I also plant petunia seeds, from Mr. Fothergills. And yes it tells me the sowing time, etc, which takes 14-21 days.

How are your petunias then? Did you succeed in growing them? How long do they grow from seed? I sown the seeds since last month but until now they are still not sprouted! :( I have followed the instruction though

And now I can't find the seeds because they are so tiny, first their colors are white and sticky, but since every day I water them their white coats seem to melt, leaving the inner brown seeds and the soil is now look empty :(

Your petunias are amazing!! Wow... I hope one day my garden will be as colourful as yours.
So the key is patience and not to worry,,,even plant in nature are self seeded..
Btw yesterday I saw in pinterest about someone who has germinated her petunia seeds in just 4 days, by sowing the seeds in coffee filter and keep it in moist inside ziplock.
Maybe I will give it a try, hope my petunias will sprout too :)

Just had to comment on your beautiful home and yard. The plants all look so healthy and well kept. It's obvious that you love plants and have learned to grow and care for them in a way that keeps them happy and looking so beautiful! They may not be able to speak, but I know they love you too :-)

Art