Yeah i decided to train farming, im 46 and got there all by exp lamps, i need 47 for ardy diary so i just gonna grow some herbs since i think you can make profit with them, now im wondering. How long does it take for Irits to grow so i can harvest them? And is it the same time for all the herbs? Im completly knew to farming, i havent grow a thing other then for quests and achivement diarys. I need to know please.

Approximate time would be around 75 minutes for all herbs. I personally use amulet of nature on the last farming patch on my run. I find it very helpful when it announces when it's ready (since it's last patch it means that all other patches are ready too, unless diseased).

Do i need to wear the ammy all the time or only when im planting?

you click the ammy and use it on the patch and then you just have it with you so you can check it. You dont have to wear it the whole time.

If that one level for the diary is all you want, you might simply take a sip of Greenman's Ale, which will take you up one level. This might work for you.