12 to 18 inches if you dont have 10feet of height.
1]age dosent matter if you true leaf is at set 5 or more,
or
2] from clone can go to 18 to 20 inches,
or
3] age of mother has started alternate node structure.
or
4] if your plant count is small you can stem split and spread out the shoots[leaders] and go for north,west,east,south, budding sites. no one here talks about n.s.e.w. growing.
keeping all your tops at even height is critcal as they will all think they are main stem and grow big, you just have to have the best lighting and the best sub base[root area] for max yeild. nutes dont really matter all of them out there are good, IT IS HOW YOU USE IT FOR THE STRAIN AND ENVIRONMENT YOU GROW IN. the best easy forgiving one is by general hydroponics, flora series, it works great for hydro,soil,soiless, or any type of system. or if money an issue then use miracle grow, thats stuff is cheep and highley concentrated, just never NEVER,never, use nute formulas that say 1] time release, 2] self adjusting ph. THATS ALL CRAP ,IT IS A SALES PITCH. if hydro stores and online companys wanted you to grow the best shit ever, THEN WHY DIDNT THEY SELL YOU EVERYTHING YOU NEEDED AT FIRST. they want you to come back and buy more shit.microbes are very very very important, so dont belief if they tell you it has everything in it. they are lieng, it cant be done, why, some of those critters eat each other up , the best shit is a combo of microbes, fox farm micro brew,then add, gh sub culture m, and gh sub culture b, gh=general hydroponics, PLANTS AS THEY GROW NEED DIEFERENT PH AND DIFERENT NUTRIENTS DURING THERE LIFE CYCLE, UNTILL YOU BEEN GROWING THE SAME STRAIN FOR ABOUT 10 YEARS WITH NO PROBLEMS ,YOU AINT A MASTER GROWER, AND DONT QUALIFY TO TEACH GROWING TO ANYONE, I BEEN GROWING OVER 42 YEARS, evry type of system in, out, everything i manage right now 88 grows in california and have started 1000's of grows in my life, i dont know anyone in this industry that has done that, it takes me 3min to read a daily log 1 week journal teach and train my growers, by crop 3 they got it wired and i rarely have to do anything. this site has a book you can down load for free called cannabis bible, i susgest everyone down load it, it is 99% correct, read and study it like your life depended on it. it will help you learn from your plants what your plants are trying to tell you. anyone can grow supper bad ass shit if they have passion for it. they only need to love the plant as much as i do. and then it is very easy to teach them, [THIS IS THE BEST SITE TO LEARN AT.] THERE ARE A LOT OF GOOD GROWERS HERE. there are alot of fakes too, lol, with that bible and some soil and a pot and water and light you can grow a bad ass plant just useing that bible alone with out any ones help. you just need the passion and forget all the crap on the internet. if you have a specif question just email me and ill show you how to do a daily log and weekly journal that is so easy i can teach you in 3 grows how to beat anyone here on this site. just pay attention and have the passion. everything is easy. sya grow help in the subject line, and ask your questions in this forum and it goes to my email. when i get a chance ill answer. i dont ignore anyone, i am just very busy helping people all week, i read journals on sunday and monday, and if we becomes friends you can text or call if you have major issues. i will teach you how to give me the info i need to see to be able to find where you went wrong at. most likely it is a ph issue 90% of the time. thats how lock outs occur . all the other problems are preventative and fixable.have fun keep growing. heres the numbers. 70% of smokers will never grow, out of the 30% that remain only 1% have the passion. only because they are teachable. people pay me a lot of money just to sit and talk with me before i give them any info,and sign a contract. i do how ever help alot of people for free. like people here on 420mag. :]