Humboldt Nutrients Roots Humboldt Roots is a highly concentrated organic root stimulant that expands the root zone during the critical growth stage. The soul of every plant resides in the roots. Many growers neglect this fact and concentrate on the visual aspect of their plants. A large yield is directly related to a plants metabolism rates. The plant metabolism rates are directly related to the root zones capabilities to uptake nutrients and fertilizers. Humboldt Roots was specifically designed to expand the root zone which results in larger yields.