Assuming you want to extract fireweed for its oil:
Fireweed (Epilobium angustifolium) is a flowering plant in the willowherb family Onagraceae. It is native to North America, Europe, and Asia. The plant grows in open woods, meadows, and on streambanks. The leaves are lanceolate and the flowers are magenta.
The easiest way to extract fireweed oil is through steam distillation. This can be done by placing thefireweed flowers in a distillation apparatus with boiling water. The heat from the boiling water will release the essential oils from the flower into the vapor phase where they can be condensed back into liquid form.