I judge the maturity of my plants looking at four things:
- Pistils turning brown. This is usual indicator of maturing but not a reliable one. They can turn brown because of various other reasons than reaching maturity. Stress from environmental factors will do that.
- Trichomes turning amber in color. You typically a collection of milky trichomes, still few clear trichomes and some amber trichomes. I never got them all to turn amber as I've waited and usually will take them down at 10% - 25% amber.
- Fan leaves and / or sugar leaves turning in color. This happens at the end of the cycle of an auto since the metabolic processes are halting and the plant has exhausted all the energy putting up the flowers. Looks like a bunch of different deficiencies.
- In DWC you can see the plant reaching its maturity from her feeding habits. When you first see the requirement of solution strength going down it is an indicator of plant entering the last stage of flowering. When you start to see her not consuming the solution at the same rate, it is usually an indicator that the plant is about to be done. These indicators are to be valued along with other signs such as brown pistils, amber tricomes and / or leaves turning in color.
Hope this helps