During the early summer, the stems themselves are hollow, jointed and speckled with purple or reddish flecks. By midsummer, they can reach impressive heights – often 2 to 3 meters (growing up to 10cm a DAY) forming thick stands that crowd out other vegetation.
In the winter the stems turn brown and become more bamboo like, but these are dead as this is a perennial.
In early spring, Japanese knotweed first emerges as small, fleshy red or purplish shoots that closely resemble asparagus spears. These new stems push quickly through the soil, with tightly furled leaves at the tips. As they lengthen, the shoots begin to unfold, revealing the plant’s vigorous growth habit.
By summer, the plant is in full leaf. The leaves are a bright, vibrant green and take on a broad, heart- or shield-like shape, each measuring up to 15 cm across. They grow in a distinctive zig-zag pattern, alternating on opposite sides of the hollow, bamboo-like stems. This growth habit gives the plant its characteristic dense, layered appearance.
In the late summer, between August and October, you can identify Japanese Knotweed as it has clusters of tiny white flowers that will begin to appear on the plant. This means they are high in pollen which is good for the bees and insects.
