Why Wheatgrass and any plants are unreliable sources of B12?

Info Source: http://en.wikipedia.org/wiki/Wheatgrass

Wheatgrass is also thought to be superior to other vegetables in its content of Vitamin B12, a vital nutrient.

Contrary to popular belief, B12 is not contained within wheat grass or any vegetable, rather it is a byproduct of the microorganisms living on plants.

 If plants are washed prior to consumption the water soluble B12 will be removed  making most plants unreliable sources of B12.