News Plants Plant ‘time bombs’ highlight how sneaky invasive species can be The sycamore maple seemed harmless for over 300 years. Then it started growing out of control When sycamore maples first landed in Great Britain, they hung out harmlessly for centuries before revealing their invasive side, a new study finds. An introduced species can take years to get moved within new regions to just the right conditions that unleash weedy powers and overwhelm native plants and landscapes.