Has the Japanese Knotweed growing season begun already? Post author:dan Post published:January 26, 2019 Post category:japanese knotweed/Japanese Knotweed control/Japanese Knotweed Warrington Japanese Knotweed doesn’t follow our British seasons. Like Knotweed Doctor’s Japanese Knotweed Removal Warrington office discovered on this site. As you can see from this picture fresh shoots have already started to sprout. When the temperature warms up the Knotweed plant sends up new shoots. It may be January, the heart of our winter season in the North West but the warmer temperatures in the city centre have triggered the tell-tale pinkish/purple buds of new knotweed growth.