Japanese knotweed evolved in one of the harshest environments on Earth – now scientists are desperately trying to find a way to destroy it. Where it does produce seeds, Japanese knotweed is prolific. At one research site in Philadelphia, the plants were found to produce up to 150,000 seeds each year per stem – most of which were found to be viable. This two-part system, with above-ground and below-ground body parts, means it's extremely difficult to control Japanese knotweed with chemicals. The most effective is glyphosate, which works by inhibiting an enzyme plants need to produce amino acids, and the...