In autumn 2016 we initiated an overwintering experiment at Kongsfjorden/ Spitzbergen (laboratory and in situ experiment) in order to investigate the capacity of kelp spores, gametophytes and microscopic sporophytes to survive the extended Polar winter darkness in combination with current and enhanced winter temperatures (0, 4 and 8°C) as well as the impact of different daylengths. Uni- and multicelluar gametophytes of all 3 tested kelp species (Saccharina latissima, S. nigripes, Laminaria digitata) had a high ability to survive 6 month of darkness irrespective of temperature, but survival capacity in darkness of microscopic sporophytes was considerably reduced at 8 °C compared to 4 and 0°C. Post-cultivation (short daylength, low light) after the winter treatment resulted in highest sporophyte recruitment from multicellular gametophytes. Cold-temperate to Arctic S. latissima recruited best at 8°C, but Arctic S. nigripes at 0°C. In situ sporophyte recruitment of all tested kelp species was extremely slow and macroscopically visible juvenile sporophytes became only apparent in August 2017 – 10 months after seeding. The results suggest a very good adaptation to the seasonal daylength regime and Polar darkness, but future elevated winter temperatures may change the recruitment potential of kelps.