Country Matters: Here's to the salt of the earth!
How does your garden grow? With the help of seaweed.
Saturday 14 August 1999
If you are a gardener, no doubt you have wondered how an extract from such horrible stuff can be every gardener's friend, the darling of the organic garden movement, and sold in most garden centres.
Long before the first garden centre was a twinkle in a nurseryman's eyes, seaweed was laboriously raked off beaches by gardeners and dug into the soil, both to help condition it and to aid plant growth. But for land lubbers, seaweed has, for 50 years, come conveniently packaged as a concentrated liquid, although also in meal and "calcified" forms.
Although we usually call liquid seaweed extract a "foliar feed" or fertiliser, in fact it is a "bio-stimulant" as Maxicrop International discovered when, 12 years ago, it began funding a variety of research projects; the objective was to achieve scientific credibility for a product which it had been selling to farmers and gardeners since 1952. In the process, it has been established that the nutrient and trace element content of its seaweed extract is very small (although artificial fertilisers can be added to it); its active ingredients are mostly betaines, which are amino acids, as well as carbohydrates and sugars. These ingredients, the evidence suggests, promote the manufacture of the green photosynthesising pigment, chlorophyll; they also increase, slightly, tolerance in hardy plants to frost and other environmental stresses such as drought; they enhance a plant's defence system, thus mitigating the effects of pest and disease assault; they encourage beneficial microbes in the soil and suppress some harmful soil fungi; they promote root growth and therefore nutrient uptake; they have even been found to improve seed germination. Is there no end to its virtues?
Apparently not. Seaweed is also a sustainable, renewable, natural resource, there is masses of it (and how!), and it not only demonstrably helps grow good plants, but also appears to lessen the need for pesticides, without itself being a pesticide. It also reinforces the advisability of feeding the soil, rather than the plant.
A number of seaweed species are used by manufacturers around the world but Maxicrop puts its faith in a brown seaweed called Ascophyllum nodosum or "knotted wrack", which grows round our shores but is, in fact, harvested in the clean, cold waters off Norway. It is collected by fishermen who cut it on a four-year rotation, so that colonies can regenerate. This wrack is dried locally, made into meal, then sent to this country, to a factory in Corby, Northamptonshire, where it is hydrolysed, a process which breaks down the cells, releasing their contents and making the strong- smelling, viscous, brown liquid concentrate. Once diluted, it can be used as a soil drench when transplanting young plants, or sprayed onto the leaves of more mature ones. The company recommend "little and often" applications. Because it is a bio-stimulant, rather than a fertiliser, it is applied in highly diluted form.
Seaweed extract is available either pure, or with a variety of inorganic fertiliser additives, such as sequestered iron for acid-loving plants, and potash for tomatoes; you can even get it with a moss killer added, for spraying on the lawn. These formulations have their uses but are not, of course, an option for the purist organic gardener. (However, "greens" need have no fears about dried seaweed meal, which can be used to boost a flagging compost heap and is credited with soil-conditioning properties, or "calcified" seaweed, made from a coral-like red seaweed, which is high in calcium and magnesium and is recommended both for making acid soils more alkaline, and improving the structure of heavy clay ones.)
For me, the great charm of the pure seaweed extract is that you can put it on at any time in the growing season. It can be watered even onto very dry soil, because there is no danger of it scorching roots. So if, on your return from holiday, you discover your garden full of lacklustre plants, then you could do worse than bring something of the seaside back to the garden.
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