Immature high

[Duff]

Guys I dunno if this is the right forum but it seemed it would fit in a few different forums so here goes,
I'm totally new to growing but recently I thought i'd give it a go so I bought some Mexican Sativa seeds as I like the cerebral high off Sativa and planted them and out of ten seeds I got 4 plants, now they seem to be going well but they are now about 4 feet tall and rising I'm growing them in my greenhouse and am wodering how long it will be before they flower as they don't seem to be anywhere near it yet and if they keep growing like this they will be through the roof in a couple of weeks?
Now the strange thing is I cut off a few of the lower leaves as they where a bit yellow and dried them and smoked them just to see and I actually got a buzz, how can this be from immature plants?
All comment welcome.

 

[Bulldog3500]

Pictures and strain names would help, if you can't get photos then more info will be needed. As for why you got a buzz off of the leaves, you got high because there are trichomes on the leafs but no ware near as many as on bud but it is there non the less which is why you should save the leafs for making butter or hash because the leafs are not very healthy to smoke.