Invasiveness evaluation of fireweed (Crassocephalum crepidioides) based on its seed germination features

In China, fireweed (Crassocephalum crepioides) is listed as an invasive plant that is also cultivated as a vegetable. To gain a clearer understanding of its invasiveness and rapid spread, we evaluated its seed dispersal ability, and the influences of light, temperature, pH, NaCl stress, moisture content, and storage periods on its seed germination. Its seed dispersal ability is limited. The seed germination of fireweed is inhibited by darkness, temperatures < 10 degrees C or > 35 degrees C, and a NaCl solution with a concentration > 0.15 mol L-1. The optimal conditions under which nearly all the seeds could germinate are light, with temperatures from 20 to 30 degrees C, and a neutral soil with 40% moisture content. The seeds of fireweed have no apparent dormancy and retain a high viability after room storage for 10 months. Fireweed only has a moderate invasive capacity and its wide distribution in China possibly correlates with its cultivation.