Most of those who guessed, guessed correctly – yesterday’s Mystery Photo was of the fruits of Japanese Knotweed (Polygonum cuspidatum), which reproduces both by spreading rhizomes (underground stems) as well as by seeds. Seed production, however, is not common, as the plants are unisexual, with male and female flowers on separate plants, and both are rarely found in the same colony. The rhizomes don’t need much help, though, as they can survive temperatures of -31 degrees F. and can extend 23 feet horizontally and up to 10 feet deep. Small wonder that Japanese Knotweed, introduced as an ornamental, has thrived and out-competed native plants. Its delicate 3-winged, brown fruits belie the hardiness of this practically indestructible and invasive plant.