18.3 Producing Female Seeds
http://www.dutch-ganja.com/sexual-variants-in-cannabis.html
If it were possible to know which seeds are female and which are male, marijuana growing would be even simpler than it is. There is not practical way to discern the gender of a seed - but there is a simpler procedure for producing seeds that will all grow into female plants.
To produce feminized seeds, the plants are fertilised with pollen with male flowers that appear on a basically female plant. Such flowers appear on intersexes, reversed females, and hermaphrodites (see section 17). Female plants have an XX complement of sex chromosomes; therefore, the pollen from the male flowers that form on female plants can only carry an X chromosome. All seeds produced from flowers fertilised with this "female" pollen will thus have an XX pair of sex chromosomes, which is the female genotype.
Although the male Cannabis plant can produce female flowers, it cannot produce seed; so there is no chance of mistakenly producing seed on a male plant. It is possible to use pollen from an intersexual plant that is basically male (XY); the resulting crop of seeds will have the normal 1:1 ratio of males to females. For this reason, choose a plant that is distinctly female as a pollen source. A female plant with a few random male-flower clusters, or a female plant that has reversed sex are both good pollen sources. The seed bearer can be any female, female intersex, or reversed-female plant.
In most crops, careful inspection of all the females usually reveals a few male flowers. And often, when females are left flowering for an extended period of time, some male flowers will develop. If no male flowers form, you can help to induce male flowers on female plants by severe pruning. One such procedure is to take the bulk of the harvest, but to leave behind some green leaves to maintain growth (as described in the section on "Double Harvests" in section 20). Most of the plants will continue to form female flowers, but male flowers are also likely to form. At times, the plants may not grow particularly well, and may in fact form distorted and twisted leaves, but they will produce viable seeds as long as some stigmas were white when pollinated. (Remember, it only takes a few fertile buds to produce hundreds of seeds.) Pollinate the female flowers by hand as soon as pollen becomes available.
{Figure 82. A solitary male flower on a female plant provides "female" pollen. (Also see Figure 84 for a female reversing sex.)} {Figure 83. Growth may not be vigorous, but seeds will form if stigmas are white when pollinated.}
Under artificial lights, turn the light cycle down to eight hours after cutting the plants back. The short cycle helps to induce male flowers on female plants.
Male-free seed can also be produced by pollen from a natural hermaphrodites. The progeny, however, may inherit the hermaphroditic trait, resulting in a crop with some hermaphrodites as well as females. This could be a problem if you want to grow sinsemilla the next crop.
