Signs of a Mature Plant

Can someone explain to me what the signs of a mature plant are? I'm trying to figure out if my plants should be put into flowering. Thanks

A mature plant will have alternating nodes - instead of nodes growing across from each other the nodes will be staggered one on one side, and one up higher on the other side.

usually after a couple of months she'll start to show pre-flowers and that should be you're sign to flip the lighting...but you could also flower as soon as she reaches you preferred height
yes also what has been stated above...staggered nodes

angelsbandit said:

A mature plant will have alternating nodes - instead of nodes growing across from each other the nodes will be staggered one on one side, and one up higher on the other side.

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I think my plants are mature then at only 3 weeks old, they have branches coming out from each side of the original branches, about 15-20 branches total per plant. Is that what you are talking about?

Alternating nodes:

One new branch on one side, the branch on the other side will be above the other - not straight across from each other.