What is the greenest flooring choice of all?

Bamboo probably is high, maybe cork.

Soft woods grow quickly, 20 years vs. up to 75 for hard woods, wear out too quickly. Oak and maple and some ash are grown specifically for flooring purposes and do good as they grow, but life cycles are much too long.

Cork is from the bark of a tree and when cut from them, does not kill them (It is almost a molting process.) or harvested as “bark” then it is harvested three years later again, but cork absorbs.

Bamboo is totally sustainable, enriches the soil as it grows and renews itself every 5 years with up to 9 times the amount of fiber as was cut down originally. During its growth, it absorbs 8 times the CO2 of any other plant of its size and therefore is also a nitrogen sink. Since the day after harvest there are up to 9 baby plants of 18 inches in height, soil erosion is unknown. As a deep rooter, the bamboo requires no watering. Since it creates great shade evaporation from the floor is low, there is only leaf growth at the very top and most insects are not very interested in bamboo. 100% of the harvested plant is used. (Pandas eat other varieties.)