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Homemade Kelp Fertilizer

On Thanksgiving morning Jon and I woke up in Oceanside, Oregon and wandered down to the wide, rock-strewn beach. Waves were gently breaking against the sand and a surfer and a sea lion bobbed up and down a few yards off shore.

The weather was calm, but the beach gave us a hint of the strong storm system that had blown through a few days before. Smashed shells and tumbled logs littered the sand. At the edge of the high tide mark we found a gigantic pile of kelp. The long, whip-like sea plants were twisted around each other like a nest of snakes.

Huge kelp forests grow under the waters off the Pacific shoreline. The forests provide oxygen, shelter, and food for seabirds, otters, fish, sea lions, seals, and other ocean creatures. Kelp, of course, is also an excellent fertilizer for plants, especially vegetables. I was tempted to gather some of the kelp and bring it home with me, but I had no way to get it off the beach and I wasn’t sure what the harvest rules were. So we swung a few pieces around like bull whips, gave Domino a chance to throughly investigate the pile, and then left it alone.

This morning I looked up the rules regarding harvesting kelp in Oregon, and I found the language bureaucratic and confusing. Individuals may harvest up to 2000 pounds of kelp for personal use from submerged lands and 10 pounds per day from intertidal areas. I interpreted this to mean that you can pick up 10 pounds a day from the beach and you can take out a boat and harvest up to two tons, all without a permit.

With what seems to be an ample source of nutrient-rich, organic material available just a short drive from my door, I’d like to investigate using fresh kelp in the garden and making my own fertilizer. But I hesitate, because I do not know what the impact of removing the kelp from the beaches and near offshore waters has on the complex ecosystem that lives within the kelp forests. Finding the kelp pile also made me think for the first time about the source of the kelp in the fertilizer products I buy and about the sustainability and regulations surrounding the commercial harvest. My curiosity is sufficiently piqued that I’m going to do a little poking around to see what I can find out.

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13 Responses to “Homemade Kelp Fertilizer”

  1. 1
    Rose Says:

    I’ve often thought about gathering kelp for homemade fertilizer, but like you, wasn’t sure whether it would be environmentally PC.

    Great photos!
    .-= Rose´s last blog ..Holiday Eats &amp Mushroom-Pecan Pâté =-.

  2. 2
    anncat Says:

    I took a class this summer through Dandelion Botanicals in Seattle taught by Ryan Drum. He’s a really great resource and can be found at He mentioned that a lot of the seaweeds we were investigating at Golden Gardens should not be consumed due to pollution. So unfortunate! Good luck with your research!

  3. 3
    Kate Says:

    Kelp is a great fertilizer because it is so rich in N. Be aware that ocean-harvested goodies are going to be laden with sodium… not something you want in your garden soil. A thorough rinse is a minimum order.
    You raise a good point about fertilizer and sustainability. Seems like most of the fertilizers on the market, including certified organic products, are resource intensive and not necessarily “green”.
    .-= Kate´s last blog ..Kale two ways – both spicy =-.

  4. 4
    Elaine Says:

    I just came across this new book by Jennifer Hahn – Pacific Feast: A Cook’s Guide to West Coast Foraging and Cuisine, which has a chapter on foraging sea vegetables. You can browse through a few chapters on Amazon, but unfortunately the sea vegetable chapter isn’t included online.

  5. 5
    Vegetable Garden Cook Says:

    Great post! Thanks.
    .-= Vegetable Garden Cook´s last blog ..Book review and giveaway- free copy Food Rules by Michael Pollan =-.

  6. 6
    My Edible Yard Says:

    Great post. I can’t wait to hear the results of your research. I, too, use a kelp-based fertilizer on my urban homestead and you’ve given me food for thought.

    .-= My Edible Yard´s last blog ..Saving Money on the Urban Homestead =-.

  7. 7
    Swamp Thing Says:

    Bull kelp is an annual species and it dies back in the fall. You won’t affect next year’s production by harvesting from the beach. But kelp decomposing on the beach does provide food and shelter for all sorts of tiny critters that are an important food source for small fish including juvenile salmon. If you picked through a pile you probably saw lots of amphipods or “sand fleas.”

  8. 8
    Willi Says:

    Anncat–Thanks for the link to Ryan’s site. Such an interesting fellow. I’m not surprised about the kelp at Golden Gardens, we once went on a tour of the Duwamish River watershed and that whole waterway is such toxic soup.

    Kate–Totally good point! I’m not sure I would have thought of rinsing the seaweed before placing it on my garden. Thanks!

    Elaine–I am definitely going to pop over to Powell’s and see if they have that book. It sounds wonderful!

    Swamp Things–I have noticed before that there are lots of insects and crabs in kelp piles on the beach, it totally makes sense that it provides habitat. I had no idea until I started looking into this that there are perennial and annual species of kelp! Who knew?

  9. 9
    R. Smith Says:

    Seaweed (five or six different kinds) end up at the top of our beach in twisted rows. Eel grass does the twisting. Sometimes in a big storm all the weed is pulled back into the sound. The weed does provide a home for creatures like sand fleas. But then my compost pile provides a home too. I harvest seaweed from these high tide piles a few times a year. It’s legal in Washington if it’s loose. I rinse it or let it sit in the rain although I’m told there really isn’t enough salt in it to adversely affect the garden. Originally, I used it as a layer in building up my beds. I used so much that my soil test was way too high in trace minerals and had to back off. Now, I add a few gallons to the compost pile. The soil test proved the richness of the seaweed and its positive affect if you use it properly. Can also use it for compost tea and mulch.

  10. 10
    Willi Says:

    R. Smith–Thanks for your great comment and information. I’m sure seaweed makes a most excellent compost booster because it is full of nitrogen and breaks down quickly. Happy gardening!!

  11. 11
    Matthew Says:

    Hmmm. I know that little sea critters use the piles for temporary homes, but as far as I’m aware someone comes and cleans them up. If that is true, then you would actually be helping the environment rather than hurting it. I’ll pose the question to my class today and see what they think.

  12. 12
    bill ready Says:

    How sad .Soon(about 15 years,the only thing left in the ocean to harvest will be seaweed/seaplants to feed the estimated billions of people whom now harvest 75% of thier needs from its waters.If sea plants are toxic “now”,we are literally doomed to mass starvation.Sorry about pointing out the facts.

  13. 13
    Sharon H. Says:

    I too am looking for regs about taking kelp from the beachs in Oregon. Need some to replentish my 9 acre cow field. Please add any additional info you get to your site.

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