Understanding the phenology of the invasive macroalga Nitellopsis obtusa (starry stonewort) is critical for evaluating and predicting its impacts on native macrophytes and timing control efforts. We tracked N. obtusa phenology in two Minnesota (USA) lakes from 2017 to 2018. We measured N. obtusa biomass and counted bulbils (asexual reproductive structures) throughout the growing season and in winter, under ice. Additionally, we compared phenology of N. obtusa to other invasive and native macrophytes using a long-term, Minnesota statewide dataset. We found consistent late-season peaks in N. obtusa biomass in both lakes, and this extended growth distinguished it from common native and invasive macrophytes in the region. Phenological asynchrony of N. obtusa relative to native macrophytes indicates use of a distinct temporal niche that may contribute to its invasion success. Bulbil counts were lowest early to mid-summer and increased through fall; however, high variability in this relationship warrants more intensive sampling to clarify seasonal trends. Late-season growth of N. obtusa poses challenges for timing control efforts, as early-season treatments may be limited to avoid harming native species. Treatment during peak biomass, before peak bulbil abundance, may improve control.

了解侵入性大型藻类Nitellopsis obtusa（繁星石苔）的物候对于评估和预测其对本地大型植物和时间控制工作的影响至关重要。从 2017 年到 2018 年，我们在明尼苏达州（美国）的两个湖泊中跟踪了钝头猪笼草的物候。我们测量了钝头猪笼草的生物量，并计算了整个生长季节和冬季冰下的球茎（无性繁殖结构）。此外，我们使用明尼苏达州范围内的长期数据集将钝头猪笼草的物候学与其他侵入性和本地大型植物进行了比较。我们在N. obtusa 中发现了一致的晚季高峰两个湖泊中的生物量，这种扩展的增长将其与该地区常见的原生和入侵的大型植物区分开来。N. obtusa相对于原生大型植物的物候异步表明使用了可能有助于其入侵成功的独特时间生态位。Bulbil 数量在初夏到仲夏最低，并在秋季增加；然而，这种关系的高度可变性需要更密集的抽样来阐明季节性趋势。N. obtusa 的晚季生长对时间控制工作提出了挑战，因为早季处理可能会受到限制以避免伤害本地物种。在峰值生物量期间，在峰值球茎丰度之前进行处理，可能会改善控制。