I remember way back in the old days somehow me thinking that in Afganistan where they were growing poppies and I seem to remember them slicing the stalks right before harvest...
Thats because thats how you harvest the opium.
Harvesting Opium
After the last petal has dropped, keep an eye on the gray band at the top of the capsule where the petals were attached. When the gray band is very dark (almost black) the opium is ready to harvest. This will be about 14-20 days after the petals fall off.
Harvesting means making a shallow cut to release opium from the seed capsule. The cut should be less than one-sixteenth of an inch deep. Do it all around the pod. As you do so, you will see little blobs of white coming out.
Leave the wounds to release opium for 3-6 hours. Then collect your opium. By now, the white blobs will have turned into yellow/brown blobs that can be scraped off and collected on a blunt putty knife or something similar.
There are better methods of making cuts so the amount of opium you get is maximized. Pages 47-51 of
opium poppy garden, describe (using text and illustrations) how to harvest several yields of opium from the plant over the course of a month.
The book also shows how to make simple tools (for making cuts, harvesting, and collecting opium) out of inexpensive items found in a hardware store or kitchen. Photos from the back cover of the book, showing the opium harvest process, are located
here.