Wild Lettuce

lactuca canadensis is a tall weed growing 4-10 feet. other names are:
canadian wild lettuce, devil's weed, fireweed, horseweed.

from gardenbed.com: wild lettuce

the whole plant is rich in a milky sap that flows freely from any wounds. this hardens and dries when in contact with the air. the sap contains 'lactucarium', which is used in medicine for its anodyne, antispasmodic, digestive, diuretic, hypnotic, narcotic and sedative properties. lactucarium has the effects of a feeble opium, but without its tendency to cause digestive upsets, nor is it addictive. it is taken internally in the treatment of insomnia, anxiety, neuroses, hyperactivity in children, dry coughs, whooping cough, rheumatic pain etc. concentrations of lactucarium are low in young plants and most concentrated when the plant comes into flower.

the plant should be used with caution, and never without the supervision of a skilled practitioner. even normal doses can cause drowsiness whilst excess causes restlessness and overdoses can cause death through cardiac paralysis.

all the best.