Seaweed for Gardens, Humans and Animals - Portnoo 7 October 2009
Please note: All seaweed photos on this page are the copyright of
Michael Guiry, Algaebase and used with permission. See Micheal Guiry's
work on the Algaebase site.
Rosario
Piseri
gave
a
talk to Donegal Garden Society on seaweed and its many
uses. She is an Algologist from Milan in Italy and has studied at
Galway University since coming to Ireland in 1996. The company Alagaran
was formed in 2005 to sell a range of products: foodstuffs,
fertilisers, cosmetics and remedies for the skin disorders.
She explained that there are red and brown marine algae. Many of these algae are very ancient organisms. It appears that seaweeds are far more complex organisms than generally realised. Many have complex tissues and growth forms.
She went on to talk about the different types of seaweed and how it was processed. Starting with:
Fucus
A
mid-shore wrack easily recognised by its paired bladders occurring on
either side of a prominent midrib. (Fucus serratus). Have medical uses
and anticarcinogenetic
properties.
Kelps: Laminara
Description: Dark brown, to 2 m in length; with a claw-like holdfast, a laminate blade to 1.5 m long split into finger-like segments.
Distinguishing
features: Oval stalk, and does not snap easily when bent; in Laminara
hyperborea the plants are lighter in colour, the stalk is generally
longer, thicker and circular it snaps easily when bent. Also Saccharina
latissima Habitat: very common in the lower intertidal and shallow
subtidal growing on rock in Britain and Ireland and may form extensive
meadows at low water.
Rosario said that the alginates present in all Laminaria species help the stomach and colon functions.
The high iodine content makes it a great ingredient for helping a slimming diet. The taste of this seaweed is quite acceptable. When cooked with legumes (beans, peas, etc.) it will neutralise the formation of unwished air in the digestive system. When cooked in sauces or soups it will be very difficult to distinguish this seaweed from any other green vegetable.
Carrageen
The use of Carrageen was first described in Ireland around 1810, when it was recommended as a cure for respiratory ailments. The name "carrageen" was introduced around 1830 and probably came from Carrigan Head in Co. Donegal. "Carrigan or Carrageen" is a common name throughout Ireland, not surprisingly since it means "Little Rock". The use of Irish or Carrageen Moss spread from Ireland to New England, USA, probably via the Irish migrants fleeing the potato famines of the 18th and 19th centuries. A small processing industry developed there that expanded enormously during World War II, mainly to replace agar, as mentioned earlier. After the war, Carrageen gradually became a major force in the food additives business, and is now the leading seaweed extract on the world's markets.
Carrageen is an ideal food additive: it has a range of gelling and emulsifying properties. In fact, a major application is found in chocolate milk. Carrageens are also very good at keeping chocolate in suspension. Rosario sells the dried bags of Carrageen as a well known Irish cure for colds but also a thickening agent in cooking.
Ascophyllum nodosum (Known colloquially as bladder wrack)
Ascophyllum nodosum
is brown seaweed closely related to Fucus. It forms single bladders
centrally in long, flattened strap-like fronds.
Ascophyllum is used for the extraction of alginic acid, a polysaccharide used in foods and in biotechnology. Plants are harvested in Ireland. In Donegal it is cut sustainably by hand for alginate production, for high‐quality meal for animals and as a fertilizer.
The alginate present in all Laminaria species helps the stomach and colon functions. (see above)
Dulse
The red seaweed / macroalgae Dulse / Dillisk (Palmaria palmata) has been used for centuries in Ireland, particularly on the North and West coast of Ireland and in Northern Ireland.
This red Irish seaweed is hand harvested from all around Ireland's shores. It is gathered at low water / tide and was traditionally air dried along the shore. Rosario has developed the system so that each Irish seaweed species has a different drying regime to preserve texture and taste while reducing the moisture content. Well known in the Irish tradition as a "salty" snack. Very common in the old times. High in Vitamin B12 is highly recommended in vegan and vegetarian diets, where the lack of this Vitamin is one of major problems.
All red seaweed contains Beta Carotenes, very useful to prevent viral attacks. Not always accepted for its peculiar taste, is very useful to enhance flavour in fish recipes. When mixed with flour, baked in bread or mixed in hand made pasta, the taste will be totally neutralised.
Seaweed and Cancer
The anti carcinogenic properties of brown seaweeds (kelps, wracks and others) are well known in some cultures but not yet understood. Traditional Chinese medicine includes the brown algaLaminaria in the treatment of cancer.
The first use of seaweed to treat cancer in Western medicine was in the 1960s, when something called Algasol T331 was used in Italy. The good recovery seems to have been improved well‐being following chemotherapy, including increasing appetite and hair regrowth. Unfortunately, no further research was done. In other laboratories, brown seaweed extracts have shown inhibition of cancer cells grown in cell culture, inhibition of cancer growth in animals that have been given chemical carcinogens and in animals that have had tumours transplanted into them. Four studies have used powdered seaweed incorporated into rat food, and found that the seaweed-supplemented diet was associated with a delay in time to tumour development and fewer tumours per tumour bearing animal.
In a number of publications using seaweed or seaweed extract or seaweed-derived components, brown seaweeds appear to have anti-tumour activity. So far it appears that seaweeds alone will probably not cure cancer, although they may be partly responsible for preventing cancers or delaying the appearance and progression of cancers. Rosario did mention some of the downsides of taking seaweed supplements in that kelp contains high amounts of iodine, and although safely eaten in small amounts, larger doses may cause health problems.
Questions related to using seaweed on the garden
Can
I just add fresh seaweed to my garden beds? Will the saltiness hurt the
soil? Would rinsing it first help? Good results using seaweed in
gardens. Kelp, eel grass, sea lettuce and bladder wrack are all common
seaweeds that wash up on beaches. The main difference between edible
seaweeds and seaweed for your garden is usually only the amount of sand
on it! As far as salt goes, it's recommended to rinse it if you can, or
if you can't then it will still be fine because of high rainfall in
Donegal. Remember that seaweed is 90% water so that there is
surprisingly little left when it has rotted. Confirmed by members who
regular collect seaweed and put it on the garden as a mulch.
How
to apply seaweed: You can apply fresh kelp directly to the soil Arrange
it as a 2 to 4‐inch mulch layer or include it in the compost pile.
Seaweed decays quickly because it contains little cellulose. What's
nice too, is that you don't introduce weed seeds with seaweed mulch.
Is
seaweed a good fertiliser?
For hundreds of years, gardeners and farmers around Ireland who live
near the seacoast have been using seaweed to improve their soils and
their crops. They recognize that plants grow better with seaweed mulch
and in soil fortified with composted seaweed. For a long time no one
really understood why seaweed was so good for the garden, but it was
obvious that it was. Over the past 20 years, researchers have begun to
discover what this wonderful relationship between seaweed and plants is
all about.
While seaweed is a form of fertilizer, researchers have found that its most significant characteristic is that it acts as a catalyst, or enhancer of plant growth. By enabling a plant to absorb nutrients from the soil more effectively, seaweed works for plants much as a vitamin pill does for humans. It simply helps the plant grow better.
Seaweed or kelp extracts provide most of the micronutrients needed by plants and soil. All living‐things require a variety of these micro‐nutrients, many in small, or "trace" amounts. Examples include boron, zinc, and iron. These minerals, present in seaweed, improve plant health, yield, shelf life and flavour, as well as resistance to stress, disease, and pest attacks. Some of these minerals may be deficient in soil. Or sometimes favourite plant hybrids and sensitive varieties just cant assimilate existing minerals, no matter how abundant. Soils which are extremely high or low in organic matter and excessively cool or wet weather may also interfere with micro‐nutrient intake. Seaweed or kelp can solve these problems.
Seaweed has other valuable properties. It contains growth‐promoting hormones. It doesn't leach out of the soil readily and it has a slow release rate. It is a great source of vitamins and beneficial enzymes for virtually all plants. Spraying plants with seaweed extract stimulates leaf bacteria thought to increase the rate of photosynthesis. In short, it does many very good things for all the plants in gardens.