Japanese knotweed (Fallopia japonica) is a tall, aggressive, perennial, invasive plant often found in dense, rhizomatous thickets. It is one of the most difficult plants to eradicate and can be found in the wild or in gardens across our region.
The most common method of identification of the plant japanese knotweed characteristics is its hollow bamboo-like stems that can reach 3 metres in height and a flowering canopy of reddish-purple leaves. It can also be identified by its crinkled leaves, and zig-zag pattern of stem growth. It is a very hardy plant that can be spread by its rhizomes as well as from seed and stem/root fragments. Once established, the weed is able to spread rapidly in its native environment, disrupting natural habitats and creating monoculture stands that displace indigenous species.
It is a rhizomatous plant, which means that it forms a network of roots and shoots that store energy and nutrients for future growth. This survival strategy is designed to allow the plant to survive under unfavourable conditions such as drought, where normal shoot growth may be reduced or stopped.
Japanese knotweed rhizomes can grow a few feet deep and spread over a wide area of ground. In the winter, it will be dormant, however it will still continue to store energy in its rhizomes until the weather is warm enough for new shoots to develop.
This is why it can be so difficult to remove an established plant, even if all the visible aboveground parts of the plant have been removed. The rhizome system will re-grow if there is any soil contact, and this makes it very important to ensure that all of the rhizomes are completely removed during treatment.
The erect, bamboo-like stems of the plant are hollow and resemble bamboo shoots. The leaves are alternate and egg-shaped, up to 8 inches long. In the summer, it produces small white flowers that form in elongated clusters in the leaf axils. Once the plant has completed its reproductive cycle, it will produce seeds that can lie dormant in the soil for many years until conditions are suitable for their germination. If you suspect you have a knotweed problem, it is best to seek professional help to make a diagnosis and provide recommendations for control. A licensed invasive plant specialist can assess the site and recommend the best course of action for your situation. This can include herbicide treatments or digging out the entire rhizome root system. This is a very intensive process and requires multiple years of monitoring and follow-up treatments to ensure that the weed is fully eliminated from an area. This process is particularly recommended if there has been previous ineffective treatment of the plant. This will ensure that the invasive plant is not reintroduced through the same methods of spread. The KISMA staff have extensive experience treating knotweed and can offer recommendations that will work in your unique situation. For further information on the services we can provide, please call us at (519) 783-6555.