Japanese knotweed identification becomes much easier when you are aware what the plant looks like at various stages throughout the year. Japanese knotweed grows in the spring, with new shoots emerging in red and purple colours that closely resemble the spears of an asparagus. The leaves will be rolled up and dark green or red.
During the summer months the leaves begin to change into the shield shape and can be up to 15cm long. It is during late summer and early autumn when the white flowers begin to bloom, and the stems are mostly hollow and form in the zig-zag shape mentioned.
As we move into the autumn the leaves remain in place but will begin to change colour into yellow, and the stems will turn brown. The plants can still reach 2-3 metres in height during this period.
Winter is the time when knotweed canes begin to die, and the weed becomes dormant in nature. The leaves will go from yellow to brown, and eventually fall off, whilst the canes are so hollow that they can collapse.