Once the female flower heads are well developed, we can use a trick to encourage the plants to produce higher THC amounts. This is so-called splitting. It can also be used on plants grown from seed. The right moment is when the first seeds are fully ripe. This splitting technique comes from Southeast Asia and works as follows.
At a height of 20 to 25 cm. above the ground, wind a piece of string under the lowest branches fairly tightly round the stem. Then press a sharp knife in the fibre direction through the stem, just under the string. We draw this knife down to around 5 cm from the ground. Don't pull the knife quite out. The stem is now split down the middle over a length of about 15 to 20 cm.
Next push a stick about the thickness of a pencil through the split. This is best done by pulling the knife back again to slightly above the middle of the cut and then tilting the blade. Both halves are prised slightly apart, so that we can poke the stick fairly easily through the middle. Bring the knife back into a straight position and pull it out. The stick has to ensure that the two halves of stem cannot snap back together. The string above the cut is to make sure that the stem does not tear any further.
This procedure has the effect of disturbing the upward flow of sap in the plant. This does not kill the plant, but it does mean that fewer nutrients and water are carried to the buds. As a result of this the vegetative growth is halted, in place of which the glands now secrete extra THC to prevent stronger dehydration.
I have seen photos showing how the buds become fuller and harder when compared to plants that have not been split, but this was with plants grown from seeds so for geno- and phenotypes this is not a reliable result. A good test for this is to use clones and try to keep them as identical to each other as possible for comparison.
Earlier in the story we mentioned using a pencil but if the stem is not wide enough you can use sate (barbecue) sticks instead. The point is that it does not touch the stem, but with fatter (outdoor) plants/stems you can maybe try and use something thicker.