![]() ![]() Fragments can be dispersed along waterways during flooding events or by the movement of soil containing root fragments. While some populations also reproduce via seed, colonies of knotweed are usually formed from an interconnected, underground system of horizontal roots called "rhizomes." These rhizomes are prone to splitting when disturbed and each fragment is capable of forming a fully functional clone of the parent plant. The key to Japanese knotweed's success is its ability to spread vegetatively through its root system. Another nonnative but not aggressively invasive species, broad-leaved dock ( Rumex obtusifolius), could also be confused with young knotweed shoots, but broad-leaved dock consists of a rosette of many basal leaves emerging from a central taproot, differentiating it from Japanese knotweed's many single, rapidly elongating stems. In cross-section, bamboo stems are also jointed, but much woodier, while living knotweed stems are herbaceous and will be visibly wet upon cutting. Unlike knotweed, bamboo has slender, papery leaves that persist year-round. Knotweed is often confused with bamboo (subfamily Bambusoideae), another invasive plant. Japanese knotweed leaf shape showing squared base and zigzag stem growth. ![]() Giant knotweed leaf shape with curved base. New shootsĮmerging in early spring, the young growth is especially bright red or purple and tipped with many furled leaves that are distinctly triangular.Ĭut stem showing hollow interior between nodes. The fingerlike clusters are 3 to 4 inches long and consist of several dozen five-petaled, aromatic flowers. In late summer, white or pale green flower clusters sprout from the nodes. Giant or hybrid knotweed leaves will grow much larger, up to 1 foot long, and have a rounded leaf base. Japanese knotweed leaves can be up to 6 inches long and have a squared leaf base. Many alternately arranged, spade- or heart-shaped leaves emerge from nodes along the stem, though lower leaves are often shed as the plant grows. Portions of the stem bearing leaves appear to zigzag from node to node and form dense thickets. The stems are otherwise smooth, bright green, and often covered with darker spots or streaks. Superficially resembling bamboo, its jointed, hollow stem has many red or purple nodes where the leaves are attached. Growing up to 11 feet tall, knotweed can spread horizontally via an extensive network of underground rhizomes, along which many shoots will sprout. ![]() Its close relative, giant knotweed ( Fallopia sachalinensis), is very similar in appearance and ecology, and the two species form the hybrid bohemian knotweed ( Fallopia × bohemica). Knotweed is a highly successful invader of wetlands, stream corridors, forest edges, and drainage ditches across the country. Polygonum cuspidatum), an herbaceous perennial member of the buckwheat family, was introduced from East Asia in the late 1800s as an ornamental and to stabilize streambanks. Japanese knotweed ( Fallopia japonica syn. ![]()
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