The seasonal growth pattern results in annual growth rings or lines in the stipe, which can be used to age the plant. The species may occur as an annual opportunist.

Mobility
The majority of Laminaria saccharina plants are permanently attached to the substratum. This may include bedrock and large boulders down to pebbles. Even sand grains can provide an attachment sufficient enough to allow the young sporophytes to segment and develop into new plants (Burrows, 1958). However, Burrows (1958) also described large populations of 'loose lying' Laminaria saccharina in Port Erin Bay, Isle of Man, which showed no signs of ever having been attached. She concluded that, apart from at the earliest stages of sporophyte development, an attachment to the substratum is not essential for the growth of the plant.

• Each sporangium contains 32 zoospores that develop into microscopic dioecious haploid gametophytes.
• The gametophyte goes through a 'dumbbell' stage before enlargement (female) or division (male). This stage is characterized by swelling at the distal end of the germination tube, which is separated by a cell wall from the original spore case from which the tube initially arose (Kain, 1979).
• Lüning (1990) recognized three stages in the development of gametophyte:
  (1) germination of the embryospore to form the gametophyte;
  (2) vegetative growth of the gametophyte to form either a larger single celled female gametophyte or, in the case of male gametophytes, a few small cells, and
  (3) the reproductive phase. If environmental factors do not induce fertility in the gametophyte (see factors affecting reproduction below), filamentous growth occurs.
• The filaments of female gametophytes are, on average, approximately 10 µm in diameter and those of males are usually half of that (Kain, 1979). Male gametophytes are more branched than the females and have more numerous, smaller and paler cells.
• If the gametophytes become fertile, male gametophytes develop antheridia that produce sperm. The females develop oogonia in which the egg develops (Birkett et al., 1998). This egg is subsequently discharged. After the egg has emerged, the cell wall closes behind it and forms a cushion on which the egg is seated (Bisalputra et al., 1971).
• The external egg is fertilized by the motile sperm and the resultant zygote eventually develops into the new sporophyte.
• After fertilization, a thick cell wall is formed around the zygote and when the zygote reaches 10-16 µm in diameter, it starts to elongate rapidly (Bisalputra et al., 1971).
• Sporophytes first become attached by filamentous rhizoids but later by large branched haptera (Burrows, 1971).
• After rhizoid attachment, an attachment disc is formed from the swollen base of the stipe (Kain, 1979).
• Cell division in the young sporophyte gives rise to a broad flat thallus but eventually a meristem gives rise to a flat blade above it and a cylindrical stipe below (Burrows, 1971). By this stage the plant has taken on the recognizable 'kelp shape'.

• germination of zoospores was inhibited at 20 °C;
• gametophyte growth improved with increasing temperature between 4-17 °C;
• fecundity was totally inhibited at 20 °C;
• sporophyte growth was inhibited at 17 and 20 °C, and
• temperature for optimal growth depended on the time of year.