Fat, red-speckled shoots of Japanese knotweed, like a forest of blood-spattered asparagus spears, emerge each April from a mound of dead canes to form a jungle of 10-foot-tall plants. Their rhizomes spread underground 25 feet in all directions, sending up shoots tough enough to pop through pavement. If rhizomes reach a brook, bits break off and take root miles downstream. When rhizome-infested soil is hauled away by ditch-digging highway crews and later used to fill a washout, a new jungle will sprout there.