Primarily a biennial plant – producing arosette the first year and a flowering boltthe second – but can also be a short-livedperennial, blooming for a few years beforedying. Spotted knapweed can self-pollinateand is also cross-pollinated by insects. A prolific seed producer – individual plantscan produce over 140,000 per year – controlis extremely difficult on established infestations.
Himalayan balsam is a summer annual of riparian areas which reproduces by seed only. Native to the western Himalayas, it was introduced to Kew Gardens in the early 1800s. By the 1900s it was already common in south-west Germany and spreading via the Rhine River3, and throughout candinavian
countries by the mid-1900s. Today it is widely known as an invasive alien in temperate areas of Europe, Asia, North America and New Zealand. In Alberta there are patches along water courses within the cites of Edmonton & Red Deer, and Parkland County.
Himalayan Balsam (