The vegetative stage: building the plant before flowering

This is the stage where you shape the plant. The bigger and better-shaped it is now, the more flower sites it’ll have later.

Light schedules

• 18 hours on, 6 off is the standard and saves electricity.
• Some growers use 20 hours on for autoflowers or to keep a cool room from dropping too low.
• 24 hours of light isn’t necessary for most grows.

Feeding

Start gently and let the plant tell you what it wants. In Saloner and Bernstein’s trial with one medical-cannabis cultivar in perlite under an 18-hour day, vegetative growth was best at 160 mg/L elemental nitrogen among the rates tested. That’s not a universal feed recipe or a total-PPM meter reading. Very low nitrogen cut biomass sharply, but more than the plant needs doesn’t help.

Moving to a bigger pot

• Transplant when roots are holding the soil together and leaves reach the pot rim.
• Pre-moisten the new pot and let the old one dry slightly so the root ball slides out whole.
• Make a hole the size of the root ball, set the plant in, and water around the edge.

When to flip to flowering

A common approach is to flip when the plant fills most of the horizontal space and has about half its height left. Height gain after the flip varies a lot with cultivar, size and environment. Doubling is a planning rule of thumb, not a biological rule.

A separate greenhouse study on large Topaz plants found some canopy treatments improved cannabinoid uniformity between sites. That doesn’t prove every training method or schedule increases yield. See the training guides.