If you live in Idaho, Oregon, Eastern Washington, or Montana, you will recognize the wildflower "arrowleaf balsamroot", which is in full bloom in the foothills around Boise right now. My friend Marc and I tried to dig one out one time, with the tap root intact so we could transplant it . It had a taproot as big as your arm, and we found it to be more than 4 feet deep. We gave up on getting all of it, so it might have been 6 feet deep or more. The Indians pounded the root to obtain the starch, and made a paste out of it.