Species of Striga (witchweed) are known to leave some of the highest seed densities in the soil compared to other plant genera; this is a major factor that aids their invasive potential.[8] Each plant has the capability to produce between 90,000 and 450,000 seeds, although a majority of these seeds are not viable.[9] It has been estimated that only two witchweeds would produce enough seeds required to refill a seed bank after seasonal losses.[10]