Farmgirl Confidential: Seaweed
When I was a child our 1800s home was not insulated. It was some chilly on windy winter nights. The windows rattled and the wind whipped up through the wide, open cracks between the floorboards. My glass of water was frozen on the windowsill in the morning. My grandmother suggested the logical cure for drafty old homes, what everyone always did when she was growing up: bank up seaweed against the brick foundation. So we did. In spring, the seaweed was raked back and pitched into the garden as compost.
Old town records from Simon Deyo’s History of Barnstable County, published in 1890, confirm the heavy use of seaweed on the Cape in numerous comments of how outsiders were perplexed with the locals’ many uses of the “refuge washed up by the sea”. In summer my mother would send me out onto the beach with a little bucket to gather certain seaweeds for her so she could make us seaweed pudding (look for John Carafoli’s article in the Spring 2011 issue of Edible Cape Cod for a great seaweed recipe).
So seaweed has just been a natural part of my life as a gardener and then farmer. I never really knew why its applications to the garden worked so well, I just saw the results of what happened if you didn’t use it. granted, the fish dug in every spring did a heck of a job of producing superior vegetables, especially corn, but still there is just something about that seaweed.
As it turns out, it actually has myriad scientifically-proven benefits. First and foremost it conditions our sandy soil, binding soil particles together and helping to hold nutrients and water. The alginic acid in the seaweed combines with metallic radicals in the soil to form a polymer with greatly increased molecular weight. One might describe the process more simply, if less accurately, by saying that the salts formed by alginic acid with soil metals swell when wet and retain moisture tenaciously, helping the soil to form a crumb structure. Seaweed is an organic storehouse of over sixty naturally occurring major and minor nutrients, plus amino acids.
Seaweed has also been found to increase plant hardiness and resistance to adverse environmental conditions, such as early frost, extreme heat and lack of moisture. Foliar feeding of plants with seaweed emulsion feeds the beneficial micro-organisms living there, helping to thoroughly colonize the surface of the plant leaf, excluding fungus and diseasecausing bacteria.
Every fall the race is on to gather seaweed. Most brown seaweeds can be used, but I prefer eelgrass. Eelgrass washes up generally between October and May, but not always. Sometimes there is nothing but Codium (an invasive species wreaking havoc in our native eelgrass beds). Codium is a green, spongy, finger-like alga introduced from Japan.
As an agricultural amendment it has little if any benefit. The invasion of Codium is endangering our shellfish beds, smothering oysters and other shellfish and blocking sunlight in eelgrass beds. Codium is a whole other story in itself.
During the coldest, windy days of winter we’re on the beaches pitch forking and dragging seaweed and loading it into trucks. Sometimes we’re able to use tractors and dump trucks, and that is a real help as, on average, I use five or six large dump trucks full and still run out. I’ve even resorted to bringing my rams to the beach with me to butt trash cans full of seaweed up to the truck (they really enjoy that!). But I tell you it’s worth the agony of getting it; money just can’t buy the benefits of fresh-harvested seaweed. Fresh seaweed is even more beneficial than processed. If it’s a bit too decomposed and stinky, I tend to mix it in the compost pile and let it degrade even more, but if it is light, clean and pure eelgrass I make long low windrow piles and save it for mulching the garden, the best way, in my opinion, to use it. You have to turn and spread the pile a few times before the growing season begins so that it won’t start to decompose; you want it light and fluffy for mulching.
I never wash out the salt. The rain may wash out some, but I have never found that it matters. After the growing season ends, most of the seaweed mulch has disappeared and has become part of the topsoil. I mulch at least five inches thick to start, adding more as the season progresses.
In the greenhouse, it’s a different story. I can’t use fresh seaweed in starter trays, but I discovered an alternative: hydrolyzed fish and seaweed emulsion. used as a seed inoculant, it increases and accelerates germination and enhances the rapid development of a healthy root system. Later on I apply it as a foliar spray out in the field to all the vegetables. grower observations indicate increased marketable yields and improved shelf life on fruits and vegetables. I see an improved condition to my plants within a day or two and, as an added pleasure, the yard smells like Chatham Fish Pier for a few hours after. I also mix fish meal and seaweed powder into my growing mix upon the second transplant. Fishmeal is a great soil conditioner and bacterial food to help feed the soil microbes.
For centuries, seaweed has been used as a fertilizer. george Owen, writing in the sixteenth century, refered to “drift weed” in South Wales, England: “This kind of ore they often gather and lay on great heapes, where it heteth and rotteth, and will have a strong and loathsome smell; when being so rotten they cast on the land, as they do their muck, and thereof springeth good corn, especially barley…After springtydes or great rigs of the sea, they fetch it in sacks on horse backes, and carie the same three, four, or five miles, and cast it on the lande, which doth very much better the ground for corn and grass.” In Jersey, England, the special flavor of their new potatoes is thought to derive from the seaweed they spread on the fields locally known as Vraic (Wrack). The seaweed is also thought to suppress eelworm in the potato crop and has been collected and spread by the Jersey farmers since the twelfth century.
Seaweed is also very attractive to my ducks, chickens and sheep. When I brought home my first sheep, a Scottish Blackface, and was researching the breed’s history, I discovered that seaweed was a big part of their diet in their homeland. I began taking him and his sidekick (a Shetland Island sheep) down to the shore to try it out and indeed, they climbed along the jetties to reach the seaweeds and algae attached to the rocks at low tide. This practice of grazing sheep on seaweed was widespread in the Scottish Islands, Iceland and in Scandinavian countries. Seaweed is a great source of vegetable protein. Today kelp meal is a common additive in livestock feed and seaweed emulsion is sprayed on grazing pastures and hay fields to produce a highly nutritious fodder. Hay consumption as well as mineral intakes are sharply reduced. Using a seaweed emulsion or kelp meal on your lawn works great, too. You can make your own seaweed liquid by soaking brown seaweeds in water, stirring quite often, for two weeks to a month and then applying diluted at a two-part-water-to-one-partseaweed tea.
Growing good produce isn’t about fertilizing plants, it’s about feeding the soil life and maintaining a healthy soil food web. Seaweed used as mulch, foliar spray or compost creates a healthy environment and protective cover for soil life to multiply and thrive in. As an added benefit, both fish and seaweed are known to build the natural sugar in plants (high Brix, an indication of nutritionally superior produce). Isn’t that why we want to grow our own organic food?