When should the jungler gank a lane?

my opinion, if the person in the lane is losing trades and if the enemy is pushed right onto their tower and forced your teammate to have to farm under the tower.

just played against a garen as jax, winning 90% of the trades but his passive was dominated me in lane. the amount of health regen he had was crazy. maokai jungle and he didnt gank even though i was under my turret farming... bad jungler or what?

it ... depends...
as long as he ganked some lane, its fine i guess...not extraordinary but...fine...
you need to consider that if you feed your lane its harder for jungle to gank after that...

didnt give garen a single kill in the laning phase, he just raped me in farm, i had like 100 to his 160.

U have to consider the game as a whole.. is solo top an item reliant champ? Will he need to get fed to be effective.l, is my Adc getting kills, are they getting bullied, does mid need to go back for mana / items.. oops bot just got wiped gotta cover their turret.. ok now our blue is up, their blue is up in 30s can I give it to our apc. Which lanes are pushed, which are not. Some times other things take priority over a gank. Jax is a solid toon, garen is as well but garen takes longer to rev up.. on the other hand their vayne is 3-0 already she may need shut down.. did u ask for ganks? Were u ready? He might have been fail but he might have been trying to do his job and/or help the rest of the team.

garen isn't a problem until he gets kills.
his scaling [at the moment] is terrible.

Meanwhile jax almost only needs a trinity to be a monster.
Get a gunblade on top of that? Psh. good game.

My point was that with a solid top like jax unless the guy is a total derp or actively requesting ganks if I was his jungle about every other job I have would take priority. Garen isn't bad but he isn't great. He wont kill u unless ur greedy. As stated above jax needs all of 2 items or so to snow ball. If I was ur jungle unless u were throwing the game id pay little attention to u and make sure our mid/ Adc got fed and actively counter jungle of course.

I play lvl 2 gankers and try to coordinate early game champs up top. Nocturne gank with Red at 2 often lands a kill in top to start the top lane snowball. Bot lane on the other hand, a single kill will often not start a snowball, esp depending on lane comp (Consider ashe +1 kill with Janna VS Graves/Soraka)

As to "when" to gank... well you have to be able to read the game and guess fi you can make a kill. If your ADC is at full HP, you are skarner and their ADC is 50% life, then gank away. Conversely, you should not have Darius tower dive ezreal/Janna as you will have no chance what so ever of catching them.