Botanical description: From its origins in the Eurasian steppe, prostrate knotweed has claimed harsh, urban habitats as its own. Tolerant of nutrient poor soils, compaction and pollution, it takes hold where other plants have difficulty. Polygonum aviculare is found growing along the pathways and desire lines of public parks and athletic fields. Prostrate knotweed flourishes in tight spots by developing a taproot which allows it to support a lush mat of foliage that radiates from the crown to a considerable width. Often found in sidewalk seams, prostrate knotweed catches sediment and small debris, slowing the flow of rainwater into catchment basins. Small oval leaves run along the wiry stems that have swollen ‘knees’ at each leaf node. Its pale pink flowers are relatively inconspicuous, partially obscured by the foliage. Polygonum aviculare is an annual weed that produces flowers from June to October, with an equally long seeding period. The tiny, hard seeds can persist on a site for years before conditions allow germination. In times of famine, the seeds have been gathered to be ground into flour for human consumption, which is quite a feat considering the size. Seeds of the prostrate knotweed have also been used to flavor tea and soup in Asia.