[reaperz]

can someone explain to me why the plants on vertical grows, grow vertical instead of horrizontal? or do you need to tie every plant to make it grow vertically? i assumed the plants grew towards the light, but i didnt see any strings tying the plants up?

gravity plays a major part in that

[Sammet]

Plants possess a hormone called Auxin - This hormone is responsible for growth and is broken down by light. This process causes growth on the dark side of the plant which makes the stem bend towards the light so that the leaves can obtain the most light.

As Rk said, gravity also plays a major part in the distribution of this hormone, making the plant always try to grow against gravity and upwards (to where the light normally is)

[reaperz]

so its just confused lol, silly plant :P