The germination ecology of Helonias bullata L. (swamp pink) with respect to dry, saturated, and flooded conditions

• Germination significantly decreased with longer exposure to dry conditions.
• Helonias seeds germinated within 10–30 days in saturated and flooded conditions.
• Helonias seeds have high floating capability.
• Helonias forms floating “seedling banks”.
• Water likely serves as an important dispersal mechanism for Helonias seeds.

Poor sexual recruitment is a major conservation concern for the rare obligate wetland plant Helonias bullata L. (swamp pink). Helonias predominately occurs in forested wetlands amongst hummock-hollow topography where water levels fluctuate spatially and temporally, creating a wide variety of moisture microsite conditions for germination. To determine how moisture conditions affect the germination response of Helonias seeds, germination percentages and rates were compared after seeds were exposed to dry, saturated (stream margin), and flooded (floating and submerged) conditions in a growth chamber and field for 1–35 days. Helonias final germination percentages were greater than 50% after exposure of all conditions, except dry conditions in the growth chamber. Moisture availability at the time of seed arrival was the main factor that influenced the germination of Helonias. Helonias seeds exposed to saturated and flooded conditions germinated within a short time frame (10-30 days). Rapid germination may be important for Helonias plants in forested wetlands where variable moisture conditions can create a narrow window for regeneration. For both the growth chamber and field experiment, final germination percentages were significantly higher (p < 0.05) for floating seeds compared to those kept dry. Water likely serves as an important dispersal mechanism for Helonias seeds since they exhibit high floating capability and germinability relative to the length of time spent in the water.