Harvesting Seaweed

Sean O'Brien, Than Wood, and Rich Pederson with a wheelbarrow full of harvested seaweed.

Yes, you read that right. Over the past couple of weeks, City Farm steward Rich Pederson (far right) has been out gathering seaweed on beaches in South County and Little Compton with City Farm apprentice Sean O’Brien (left) and Front Step Farm‘s Than Wood. The seaweed that washes up on New England’s shores, including kelp, rockweed, and knotted wrack, is a prodigious free supply of organic content for soil amendment, mulch, and composting, and it’s legal in Rhode Island to collect it at public access points. Sean, Than, and Rich used pitchforks and rakes to collect their seaweed, harvesting six large garbage cans’ worth in one day for use in compost piles and gardening bed prep.

Coastal communities have been collecting seaweed for years and have long known the benefits of using it in gardens. Seaweed is high in micronutrients and growth hormones and is therefore a potent natural fertilizer when applied directly to the soil, helping to stimulate microbial activity, correct nutritional deficiencies, and increase moisture retention. Seaweed also breaks down much more rapidly than grass, leaves, or vegetable clippings, making it an excellent compost accelerator: when folded in with other materials such as straw, it helps the pile to heat up, speeding the process of decomposition and generating richer compost in less time. That’s what led one composting website to remark, “If you live in an area where seaweed is available, consider yourself blessed.” Seaweed begins breaking down naturally on the sand in sunlight, so the idea is to have that decomposition take place in a compost pile where it can enrich your garden.

If you decide to go out and collect seaweed, it’s important to only gather loose seaweed that has already washed ashore and not to pull it from the water, rocks, or tidal pools in order to preserve the marine ecosystem. Another caveat: some people believe that desalinization is vitally important when using seaweed and recommend rinsing it so that lingering ocean salt does not alter the composition of the soil and harm plants. Others believe that seaweed only adds a negligible amount of sea salt, and that the salt may actually contribute beneficial minerals. Rich used some of the seaweed he collected immediately; another batch is currently “aging” in tubs for later use at City Farm. Collecting seaweed after a storm, when it is newly washed up, may reduce the amount of residual salt.

On a related note, the city of Newport is currently exploring the possibility of using the infamous red seaweed from Easton’s Beach to develop a new biofuel that would serve as a renewable form of energy for vehicles and heating systems. The city already collects algae for agricultural purposes using a special harvester. The technology is still unproven, but seaweed may turn out to have even more uses as a natural resource than was previously thought!

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3 Comments to “Harvesting Seaweed”

  1. Totally interesting, thanks for sharing!

  2. I wish I could have done this!

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