Can Paulownia Siebold & Zucc. Become an Invasive Species via Its Seeds?

Paulownia plantations are established in large numbers worldwide for their high production of quality wood. Paulownia tomentosa is considered an invasive plant in many countries; however, other species, and mainly their hybrids that grow in plantations, are classified neither as invasive nor non-invasive plants, although the risk of spontaneous spreading of its seeds can be very great. In April and September 2022, we conducted a germination experiment where we used three species and six hybrids of Paulownia. The germination rates of all selected species and hybrids were very high, especially if the seeds were left at a temperature of +4 °C—almost 90% (April) and around 60% (September). When the seeds were exposed to below-zero temperatures (i.e., −15 °C), the germination rates were still high and, moreover, those of Hybrids were higher than those of Species. Therefore, all species of Paulownia, and mainly the hybrids, have the potential to be invasive.