Sorry man, meant the apical meristem, i.e, actively growing tissue. Also, typically what is done is that very VERY immature tissue is used, like...7 or 8 day old sprouts, they are the best. Old tissue usually isnt because it exhibits very poor totipotency. Even if technically it can be, that might just mean that one out of a thousand will regenerate.
Veg DEFINITELY better than flower. The earlier the better, but thats sort of besides the point, we're looking to isolate the genes of a really good mother...so, someone might need to try with a plant well into flower. I've not put herb on agar before, so I really cant say. I've worked with Tomato, corn, soy and cotton...and what i've said holds true for all of them.
The experience you really need is aseptic technique. you need to be able to keep things STERILE!
and think about this guys. You want to take a piece of tissue from a plant growing in your closet, with all the normal bacteria and fungus that are on everything everywhere, and put that on sterile medium? you'll very quickly get fungal and bacterial colonies growing over everything, and it will be ruined. You can TRY and surface sterilize the tissue piece with .5 clorox .5 sterile water (and some TWEEN if you can find it), but that is a harsh treatment for tissue...and will likely damage the tissue too much. SO, when this is done the plant is grown sterily from seed, then the section we want to take is cut off, transformed, and regenerated into a whole new plant (containing the genes we want it to have...but this is of course for plant transformation, not just normal cloning) I dont really know how you'd get around the sterile needs of all this, so...some brainstorming will be required.
anyways, i'm rambling...maybe i'll start a real thread about this with pictures n crap instead. Time for a beer.