Knotted wrack can be as old as
20 years, and even the oldest parts near the root (holdfast)
are usually fresh-looking and free from external growth.
Occasionally the ice can tear the plants loose, but the
holdfast is usually intact so new shoots can sprout.
Knotted wrack is quite common along northern Atantic coastlines.
Large quantities are harvested for example, in Norway and Ireland. It
is milled into flour and used as animal feed, fertilizer and within
the chemical industry for the production of food additives.