The first beautiful female pot plant I ever grew turned out to be a male. I'll never forget the day I opened the closet to see how the ladies were doing and saw that yellow pollen all over the surface of the leaves. I was sure those clusters of balls were the beginnings of a great cola bud. I'd just never seen what a developing female looked like. I knew from magazines how the mature female flower looked, but I'd never seen it grow.
When to start lookingThere's no way to accurately determine the sex of a marijuana plant until after flowering has begun. It's not until the plants begin to develop reproductive organs that there's anything to look at.
After the induction of the critical photoperiod, which is usually around 12 hours of uninterrupted darkness each day, plants begin to grow differentiated primoria. The new growth may take several days to appear. Some strains continue to grow vegetatively for several days before they slow down and start to flower. Other strains shoot up in a quick growth spurt right after the induction of this light cycle. The sure sign of the beginning of flowering is a change in the phyllotaxy of the plant. New growth has offset (or alternate) internode pairs, rather than the opposite pairs which grow during vegetative development.
Where to lookThese small growths appear at the internodes of the plant, usually right above a large fan leaf. This picture shows an opposite pair of nodes. The small white hairs are the first differentiated primordia.
As flowering continues, the female plants begin to develop the small white wispy hairs at every internode, even on the side shoots. After a few more days, the branches really start to show flower development as second and third hairs begin to appear at the node sites. These hairs are the beginnings of the mature beautiful buds we all seek. If they were to catch wind of some pollen, the small hairs would retreat back into their sheath and begin to develop seeds.
What to doKill the males before they release their pollen and ruin your sinsemilla.