When do I have to start feeding?

I'm a first timer I see info on what to use but my ? is when what's the age to start feeding I have a 12 inch plant now I'm worried about have I waited too long to feed?

depends on your medium but if you plant is happy and green you have not waited too long.

does your soil have time release nutes in it? sounds like it.

Whenever really. Some like to push as early as possible, i like ot leave it till they need it. If you're feeding them with plain water and they're still green then great, it's not to say you can't add nutes (at 12" i would) but it's only once they start to yellow from the alck of food that you actually have to start. I often let my plants go over a month before i feed them soil or hydro. If they start to pale though, give em a lil boost

Man you guys are great help!!!! Yes I got this soil from my grandfather... not sure what kind it was but I know his front yard is awesome. But yeah they are green ass hell! Thanks my friend scared me saying "Oh it needs food!" but they weren't sure either. I hate to say it but I put one mir. grow in it. So food wise whats the best food you suggest?

It was a small grow stick the ones you just put inside soil.