Effect of overwinter hydration, seed storage time, temperature, photoperiod, water depth, and scarification on seed germination of some Schoenoplectus, Polygonum, Eleocharis and Alisma species

• Effect of factors affecting germination were tested on 6 species.
• Schoenoplectus germination was best at 32–38 °C in 4 cm water after bleach treatment and cold, wet storage.
• 94–100% of A. gramineum germinated if pre-treated with bleach after cold wet storage and incubated at 20–30 °C.
• Polygonum amphibium (≤13%) and Eleocharis palustris (≤2%) had poor germination.
• Polygonum pensylvanicum germination was highest (54%) after 12 months of wet storage, bleach treatment, and incubation at 15–20 °C.

In an effort to improve fish habitat in western irrigation reservoirs, germination of seeds of six wetland plant species was investigated in two separate experiments. In the first, seeds were stored overwinter at 3–4 °C either dry or wet. In spring, these groups were further divided into four constant temperature treatments (15, 20, 25, or 30 °C) and 3 fluctuating temperature treatments (low, moderate, high). Within each treatment, seeds from a subset of species (Alisma gramineum, Schoenoplectus acutus, S. americanus) were scarified using either bleach for 1 or 5 d or mechanical abrasion. Seeds were exposed to a 12 h photoperiod in Petri plates within germination chambers for 57 days. In the second experiment, photoperiod (12, 14, or 24 h light), water depth (0 or 4 cm; S. acutus only), temperature, and bleach pretreatment were further evaluated. Cold, wet storage (CWS) and bleach treatment significantly improved germination (84 to 100%) of A. gramineum and led to quicker germination. Bleach treatment for 5 days significantly increased germination (13%) for S. acutus at 15 °C. Temperature effects varied with species. Inundation of seeds significantly improved germination of S. acutus. For both Schoenoplectus species, germination was highest at daily fluctuating temperatures of 32–38 °C. Photoperiod effects were inconsistent. Polygonum pensylvanicum germination was only evaluated in the second experiment; maximum germination (54%) was under a diel cycle of 15–20 °C after 1 year of CWS. Based on the study, effects of temperature, temperature fluctuation, water depth, overwinter storage conditions, and scarification are sufficiently known to use the data for initiating seed pretreatment for habitat projects.