Laminaria saccharina (L) Lamour. Sporophytes were monitored monthly from October 1982 to September 1983 to investigate reproduction phenology and relationshiops to growth paatterns aaat its southern limit of distribution in the northwest Atlantic Ocean (Long Island Soundd). Plants exhibited an annual growth pattern. Growth raate, bladelehgth, maximum width, area, stiipe lehgth an wet weight swhoed the same seasonal pattern and reached maximum values between May and June. Only blade thickness continued to increase tthrooughout the ovservation period. Blade dissintegration occurred dduring August and September. Reproductive sporophytes occurred throughout the observation period; the greatest frequency of appearance occurred in October (43.8%) and June (37.8%). The blade area covered by sori ranged from 2.4% (Janaury) to 6.1% (August). Meiospore release under laboratory conditions was maximum in May and minimum in July. No meio‐spores were released in August Sporulation was not correlated with meristematic growth of nitrogen content How ever, reproductive plants were generally larger and thicker throughout the sporulation period, and had a greater carbort content is spring than nonreproductive plants. Fecundity and reproductive success of female gametophytes were maximum in spring and minimum in winter. The growth of early sporophyte stages in the laboratory was greatest in early spring; however, juvenile macroscopic stages were hardly observed in the field during summer months due to warm water temperatures. “Over‐summering” of gamelophytes and / or microscopic sporophytes may account for the annual cycle of Laminaria at its southern limit of distribution.