James and the Giant Hebe

The Giant Hebes started growing in the UK in 2023, the year after the worst heatwave ever experienced. Initially the excess growth was barely noticed, but within 10 years Hebes in gardens were causing subsidence to nearby houses, they were spreading into nearby fields and after another 7 years they were endangering farming. If they were cut back they just re-grew; poisons had no effect; and the roots were near impossible to dig out. The problem has now started spreading worldwide. James is a botanist who has been working on a theory regarding their make up which, if he's right, means a simple solution can probably be found which will cause them to die. Unfortunately it requires James to climb to the top of the hebe and take samples from the topmost leaf. Other scientists think James is 'barking up the wrong tree' and ridicule his work, but every day James climbs a hebe, takes more fresh samples and patiently continues his work.