Understanding recruitment processes of invasive species is central to conservation and management strategies. Iris pseudacorus,an emergent macrophyte, has established invasive populations across a broad global range where it reduces biodiversity in wetland ecosystems. Climate warming is altering cues that drive germination, yet studies on the invasion of wetland macrophytes often ignore germination ecology despite its importance to their establishment and spread.

The dataset includes data generated from a series of experiments conducted to improve understanding of the recruitment process of Iris pseudacorus (L.) in its invasive range. We explored germination of seeds from invasive I. pseudacorus populations in California in response to seed coat presence or absence, and environmental factors. Using experimental results in a thermal time model, we derived germination temperature thresholds.

I. pseudacorus seeds did not require cold or warm stratification to germinate. We found germination was not impacted by the presence or absence of the seed coat. Germination occurred in the dark, although germinability was two to three-fold times greater under light. At constant temperature, thermal time model estimates included: 18.3 ± 1.8 °C base germination temperature; 28.2 ± 0.5 °C optimal temperature; 41.0 ± 1.7 °C ceiling temperature. Seeds exposed to 36.0 °C achieved over 10% germination, and embryos of ungerminated seeds presented 76% viability. Overall, germinability remained relatively low at constant temperatures (≤ 25%) but was close to 90% under alternating daily temperatures.

We explored germination of seeds from invasive I. pseudacorus populations in California in response to seed coat presence or absence, and environmental factors (light and temperature regimes). Using experimental results in a thermal time model, we derived germination temperature thresholds.