The 1984 paper '
Alkaloids of Peganum harmala' reported relevant analyses.
They found dried leaves to contain 0,3 to 0,4% of an alkaloid mixture of undetermined composition. The dried stems contained 0,6 to 0,9% alkaloid, of which 10% was harmine and 5% was harmaline.
Roots were 2,3 to 2,5% alkaloids, 60% being harmine and 5% being harmaline.
Combined areal parts will be mostly stem. Assuming the areal parts were harvested green and not allowed to mature to straw a full kilogram of dried herbage might yield somewhere around one gram of mixed ß-carboline alkaloids if chemically refined.
Isolating the ß-carbolines will mostly be lots of trouble for little yield, trying to consume it as a tea sounds like a recipe for vomiting and failure.
Lots of vomiting
Peganum harmala plants are best grown in the ground. Water them abundantly in warm weather of the first year and water them freely in spring and summer of subsequent years. Yield will be zero in the first year, amusingly small in the second, and it will increase quite a bit after that.