Bittercress

 Bittercress in a forest

Bittercress is a rare plant in the redwood forest. Part of the trouble is that it is extremely small, so unless you are looking for it, it's very easy to miss. Second, it is also inconspicuous. Some plants are small but quite showy. The plant actually perfectly blends with the surrounding vegetation and is hard to spot.

Bittercress (or just cress or cardamine)

The plant definitely belongs to mustard family: it has characteristic 4 petals miniscule flower and the leaves resemble that of watercress. It is most certainly some kind of a cress but I can't pin it down to the genus. I would say it is cardamine hirsuta (hairy bittercress) except it has no hair.