Decarboxylation, or "decarbing," activates the THC in cannabis. This process involves heating the cannabis, in this case, stems, at around 220-245°F (105-120°C) for about 30-45 minutes. Be cautious as these figures can vary based on your oven's accuracy, the moisture content of the plant, and the size of the stems. It's always best to start low and slow to prevent burning your cannabis.