extract is being marketed and supposedly has special benefits when
supplied with iron. The following comments are extracted from a
gardening article on use of seaweed (there are various species of
seaweed which may differ in composition that influences
biostimulation). "Seaweed is a rootless plant in the Fucus family that
floats freely or clings to rocks by holdfasts (root-like or disk shaped
plant parts that attach seaweed to rocks but don’t absorb nutrients).
Seaweed photosynthesizes the sunlight that reaches it through shallow
water and it absorbs nutrients from sea water through its leaves. Since
the ocean receives runoff from the entire earth, it contains all known
minerals, trace elements, and vitamins. This primal supermarket
supplies a more complete diet for sea plants than any plot of rich soil
or fertilizer provides for land plants. Seaweed contains 60 or more
minerals and several plant hormones. It is not however a complete
fertilizer. It has a fair amount of nitrogen and potash, but very
little phosphorus, a major plant nutrient.
Only a few seaweeds are harvested commercially. Norwegian kelp
(Ascophyllum nodosum), a brown algae is the seaweed most used in
gardening. Norwegian kelp is gathered off the coasts of England,
Ireland, Norway, and both the Atlantic and Pacific coasts of North
America where it is called rockweed. Gulfweed (Sargassum), a floating
sea plant, is harvested off the coast of North Carolina. Giant
kelp(Macrcystis) is collected in the Pacific Northwest.
Seaweed is constantly worn down by tides and eaten by fish, so it
must grow rapidly to survive. Studies at the University of California
showed that a frond of seaweed can grow a foot or more a day, given
optimal conditions. The same growth hormones that prompt such rapid
growth in seaweed , when applied to plants as a foliar spray, can
increase the rate of cell division and elongation in those plants. The
hormones also increase root growth when applied to the soil as meal or
when seaweed extract is used as a root dip.
In recent turf tests at Virginia Polytechnic Institute in
Blacksburg, plots sprayed with seaweed extract had 67% to 175% more
roots than untreated plots. Plots treated in fall showed a 38% increase
in spring growth over untreated plots and showed 52% more roots.
In tests at South Carolina’s Clemson University, seeds soaked in
liquid seaweed extract showed rapid germination, and the resulting
seedlings had increased root mass and stronger plant growth than
seedlings from untreated seeds. They also had a higher survival rate.
Soaking plant roots in seaweed extract reduces transplant shock and
speeds root growth. Seaweed foliar sprays promote faster, stronger stem
and leaf growth, and earlier blossoming and fruit set when sprayed on
leaves and flower buds."