ok, big pothead here. first things first, teas and roots and such. i hear they work but they take a while. a product called ready clean worked really well for my brother about 15X now. but now he uses Urine Lucks Synthetic Urine and it works like a charm. comes in a box with in a bottle with a temp strip on it, take a rubber band and put it around the bottle and take the hot hands that comes in the box and stick it opposite side of the bottle of the temp strip to get an accurate reading of what the temp is.
now, if they watch you, which most testing is not done in this scenario. you will need the ready clean, OR, lay off the herb now, and start taking 5000mg vitamin C and 3 doses of potent multivitamin ed until day of the test. day of the test take 5 multi's and 10,000 mg of vitamin C, drink tons of water until that day and drink some orange juice day of with water and take all vitamins.
my other brother has used the vitamin trick 4 or 5 X now. and yes, i have read a book written by a doctor on drug testing. vitamins, especially Vitamin C and the other antioxidants fool the test by turning all results to "false negatives"
the facility however doesn't know they are false results. it just turns every thing negative. now, even if you are clean, depending on what you have eaten and drank, and im not talking about poppy seeds only or medication, certain combinations of foods and substances can actually produce "false positives"
nobody wants this. so, whether your clean or not. i would always falsify my test with synthetic urine, (not the crystals in your own piss, they don't work) or masking with vitamins or the ready clean drink. these drinks are loaded with vitamins which is why i think they work. but i wouldn't take the chance of testing without vitamins, synthetic, or the drink. too much to lose.
good luck
the vitamin trick by the way, my brother was smoking within 36 hours of the test, 2 blunts of dank