eelgrass seeds

Eelgrass Life History

eelgrass seeds close-up

seed release

seed close up

eelgrass flower shoot

anther with pollen

eelgrass flowering shoot

eelgrass seeds for use in restoration

Eelgrass reproduces both sexually and asexually, with the primary means of proliferation being asexual, through rhizome expansion and vegetative growth (see more in the Growth Habit section). Eelgrass reproduces sexually via reproductive (i.e. flowering) shoots. One year old vegetative shoots differentiate into flowering shoots at some point during the winter, or possibly, the previous fall, but become distinguishable in spring to early summer. In mid to late summer, flowering shoots stand out from the leaf canopy as wiry and lighter colored stems (yellow/white) that grow above the leaf canopy.

Video clip: Moving flowers- wmf - 1.15mb

The rate of seed development is related to water temperature, in that the higher the temperature the faster development takes place. Seed release in the Peconic Estuary normally begins in late June in the westernmost meadows and can extend into early August in the cooler deeper meadows in the east. In Long Island Sound, seed release begins in late July and extends through the end of August. Eelgrass meadows in the South Shore Estuary release seeds between early July and mid August depending on the meadow’s proximity to the mouth of the inlet. To learn more about how temperature affects eelgrass, check out the temperature page.

Once a seed is released, it falls quickly to the bottom where it is incorporated into the sediment, washed away by wave energy or consumed by predators. In fact, some seeds can be consumed while still in the reproductive shoots. Seeds that successfully incorporate in the bottom normally begin germinating as the water temperature drops during the fall. Although germination may begin in November or December, seedlings are not usually visible until the following spring. In April, the first seedlings are evident as very short (1/4 to 1/2") leaves extending from the bottom. In May, these seedlings are more visible as 1 to 2" shoots as growth begins to accelerate with increasing water temperature. By late June, seedlings are typically indistinguishable from adult shoots from the previous year unless the rhizome is examined. In cooler, deeper meadows such as those off of Fishers Island, seedlings are small and distinguishable from adult shoots well into the late summer.

Stages of Eelgrass Seed Development

seed development

seedling development diagram


Next: Eelgrass as Habitat


© 2012 / Cornell Cooperative Extension Marine Program

SeagrassLI Home CCE Suffolk Home