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Seaweed? Can I make the extract?

Mérida, Yucatán, Mexico(Zone 11)

I just read rjuddharrison's blog on pest control and seaweed extract. I love all your columns by the way and this one was great. I'd love to use it but it isn't available (that I have found) where I am. What I do have is an endless supply of the real stuff, seaweed washed up on the beach.

I'm wondering if there is anyway that I can compactly (I don't have a lot of space) render it useful as a spray or additive for my plants and pots. Do I need to soak it or rinse it repeatedly to get rid of the salt? Boil it? I'm sure it would be good to compost it in mass but I don't have the space for large piles of rotting seaweed. I might be able to make a pile at a friend's house and go check on it occasionally to see if it gets usable. Any ideas?

Keaau, HI

Soak the seaweed it water to help rid excess salt, dry it and grind it to a powder and mix it in your soil.

To make a soluble extract you will need to digest the stuff in buckets that you can close. Stir the digesting mass regularly, when it is completely digested into a black liquid, you can strain the liquid and use it wet or dry it into a powder. The whole process is time consuming, and it stinks something awful!

Mérida, Yucatán, Mexico(Zone 11)

hmmmm, I can well imagine the smell having experienced the piles of rotting seaweed on the beach after hurricanes. I think soaking, drying and grinding are the way to go for me.

We are going north at the end of this month and I'm starting my list of stuff to bring back, I might add some of the seaweed extract to the list. Crossing borders with fertilizer is sometimes iffy but I think I can put it somewhere in the RV that isn't obvious.

Keaau, HI

Maxicrop Dry Soluble Seaweed Extract is worth the while. It comes in pint containers and would look good on the spice rack next to the hot sauce!

Mérida, Yucatán, Mexico(Zone 11)

Exactly! My theory is to put anything you're not sure of out in plain sight but surrounded by mundane stuff that no one looks at. Volunteer nothing is the other part, I never lie but I never ask either. Always better to beg forgiveness than ask permission when dealing with the bureaucracy. Then again, I never have anything that I'm not willing to hand over or that I know to be illegal. I've got Maxicrop Dry Soluble Seaweed Extract on the shopping list for the US.

Keaau, HI

Sounds like you are a well seasoned traveler!

mulege, Mexico

I have collected a lot of seaweed and used it in two gardens here.

I used to rinse it. Then we had an expert on soil visiting from San Diego and he said if you wash it you will rinse out the potassium. He also said that if you have worms you're soil is fine. That worked for me. I had lots of worms. From them on we composted the seaweed without rinsing. My biggest regret in moving from that house was that I couldn't take the soil with me. It went from a clay/sand mix that repelled water to a wonderful sponge that could absorb our occasional but torrential downpours.

The YouTube video "greening of the desert" says that the permaculture method they used rendered the salt in the soil inert.

Eric at emamerica tells me that EM also renders the salt inert.

At the present time, I have a friend who is bringing me seaweed by the truckload. It is only on our beaches here for a few weeks in the spring. We spead it out and let it get dry enough to put through the chipper/shredder (my new garden toy and I love it). I am filling a couple of 55-gallon drums with the shredder seaweed and adding EM to make seaweed bokashi.

I am hoping that I can mix some of the bokashi'd seaweed with shredded palm trunks to use as a mix in my homemade Earthboxes.

I have also made seaweed extract by adding EM to a small, airtight container and allowing it to steep for a week or so.

Seaweed can also be used to heat up a compost pile. Layer it in with he the other ingredients and wet it down.

I just read on another thread where someone said that seaweed is more of a "tonic" than a fertilizer. I'm not sure what that means. I have always understood that it was a good fertilizer.

A lot of my reason for going to the trouble of getting a lot of seaweed to add to our depleted desert soil is reading Eileen Caddy's (or is it Cady?) books about Findhorn. They transformed poor soil, mostly through the use of seaweed. The conditions were very rustic and they probably didn't have access to enough fresh water to rinse it.

I'm real interested in hearing how other people who have access to seaweed are using it.


Tavernier, FL(Zone 11)

I started gathering seaweed from a friend's yard on the oceaside in the Florida Keys last fall that had already been rinsed by the rain and decomposing. I am using it to build up my garden beds for flowers, veggies and trees as there really isn't any natural soil here other than sand and fill on top of caprock. I just toss it on and mix or layer. Does not smell and have found worms. So far, I have not seen any negative consequences and since I am a beginning gardener I don't have any previous experience in what to look for. I would appreciate communicating with anyone who has worked with seaweed as a composting material or other uses in the garden. Looking forward to hearing from you!

Mérida, Yucatán, Mexico(Zone 11)

I'll try putting some in my compost bucket and making a pile at the beach that will hopefully be rinsed soon by the rains.

I had to google EM, it sounds a little too good to be true. I'm always dubious about something that says it can do anything. Especially when they said something about putting it on your electronics to prevent EMF. Sounds a bit like a tin foil hat.

mulege, Mexico

I thought it sounded like snake oil myself, but first heard about from someone whose opinions are often right on and my plants are doing well with bokashi. There are a couple threads about EM and bokashi in the Soil and Composting Forum. I started small, liked the results and keep finding that it does actually do a lot of different things.

My dogs love it, especially with fish. And it's a great grease cutter.

It is funny telling new people about it, though, because it can be used so many different ways that it does sound suspicious.

There is a code posted on the EM thread that will get you a 10% discount at


el arish, FNQ, Australia

Katiebear, it's a tonic because it is filled with growth compounds. I kelp everything including myself lol. Here's a good seaweedlink:

mulege, Mexico

Thanks, Ann. There's a lot of good information there.

My first 55-gallon barrel of shredded seaweed that I treated with EM has lots of nice white mold. From what Geoff Lawton says in "Greening the Desert" (on YouTube) enough microorganisms will nuetralize the salts so if I run out of EM I will at least compost whatever is left.

It was funny about the man who got into studying seaweed to prove it was "snake oil." Liek our fears about EM. Seaweed plus EM - double snake oil?


Lee's Summit, MO(Zone 6a)

Don't forget to add mesquito dunks/preventatives to the water or they will lay eggs in the water, hatch out and eat you ALIVE! LOL Ask me how I know!!!

Keaau, HI

Alright! Tell us all about it Kay!

Lee's Summit, MO(Zone 6a)

I think I just told you my experience!

el arish, FNQ, Australia

More and more agronomists all over the world are moving away from NPK and towards healthy soil. Seaweed has been proven as an excellent soil builder for centuries. Here's a link to an example from my people:
I don't know why organics, building soil and treading lightly on the earth seem often to be confused with some sort of Hippyhappy Utopia. It's just common sense with a strong foundation in soil science.
Believe me there's nothing hippyhappy about banana farmers in rural North Queensland and yet more and more (including the BIG farms) are using soil inoculations and foiliar sprays. Mostly because fert, fungicide and pesticides have gotten so expensive. Ann

Keaau, HI

Hey Ann, I like seaweed! It make my plants healthy! And I ain't no hippie!

But then I do like Jimi Hendrix on the guitar.

How about a good day of farming, followed by an electric blues concert? Buddy Guy & John Mayer sound good!

el arish, FNQ, Australia

Dave, I love Jimi Hendrix so your CD collection is welcome here anytime :)

My big issue is the purposeful confusing of biodynamics and permaculture with off with the fairies agriculture. We use gravity feed water, solar hot water and sustainable agricultural practices. We have a big veggie garden, chickens and ducks and catch our own fish. We have one vehicle. To us it's just common sense. I'm amazed at how many growers come out to our place and come up with theories as why we grow things so well. We can tell them until we are blue in the face that it's because we use lots of organic matter but they simply refuse to believe. They confuse our simple lifestyle with idiocy. It used to aggravate me but now I just shrug and laugh.

I have nothing against hippies either. Problem is in my area too many
people talk the talk but don't walk the walk :)

Keaau, HI

Seaweed is good for plants and people!

Organic matter and worms work together to produce humus, which contains fulvic acid. Fulvic acid grows plants; it causes the absorption of nutrients.
For a soil to be healthy, it must contain a lot of organic matter. It causes cation exchange, produces humus, and harbors beneficial bacteria and mycorrhizae

Thumbnail by Metrosideros
el arish, FNQ, Australia

Check out this product. Our government is pretty cluey and will pay for farmers to do a Certificate in Sustainable Agriculture with these guys. I'd like to enroll just have to work out the logistics. This link is to a product that has it all Do you have companies like this one in the U.S. ? Ann

Keaau, HI

Yes Ann, there are several companies making similar products.

I use "Farmer Gone Nutz" brand fulvic acid; Maxicrop Liquid Seaweed; Foxfarm Earthworm Castings & Bat Guano; Atlas Fish Emulsion and Bloom Promoter.

I mulch all my trees and garden beds. I produce better food than folks who take care of their gardens with weed-eaters and granular fertilizer.
If you feed the soil, the plants in it feed you!

Aloha, Dave

Christiansted, VI(Zone 11)

I was gathering some seaweed off a beach, and there were earthworms in the sand underneath! Must have been fifty feet from the clay soil on land, nothing but sand, and there's earthworms! Mmm, mmm, mmm.

mulege, Mexico

We have burried seaweed in the garden without washing it or composting it and we had lots of worms.

I am using the first 55-gallon of seaweed which was treated with EM. We are using the barrel now for fish scraps and seaweed. With EM. Em is microbes and they change the compostition of the weaweed and fish so that flies and mosquitoes are not as attracted it it. It also innoculates the material that is treated with good microorganisms.

My experience says that washing the seaweed is not necessary and may remove some of the minerals. I also believe in doing the least work necessary to get the job done. I would be interested in knowing what people who manufacture seaweed extract remove or add.

For making extract in a small space I would dry it and powder it then innoculate it with EM. I'm lucky to have lots of room so we can get it about half dried them put it through the shredder and go from there.

While I have lots of space we are in a desert which means limited water. And I'm in a small twon in the middle of the Baja penninsula in Mexico so I simply do not have access to many manufactured products.

Ann, thank you for the links. Good information.

I have just made a second batch of biochar. I am innoculating it with a seaweed, fish, EM mix. I don't keep good records or do "scientific" experiments. I can report that fruit trees that I planted two months ago are trying to produce flowers and fruit. I have to tell them to wait, plase, first year is for roots.

So far the seaweed does not seem to have killed anything.

It's been several years since I've been able to get any qualtity of seaweed. This year I'm getting it by the truckload along with fish scraps. Tony and I are working to prepare planting areas. We are challenged by being on a small hilltop with Arroyos on three sides and five dogs who like to help dig. However, things are moving along and I have some vegetables growing along with lots of fruit. Amending the soil with the seaweed leads to immediate growth spurts.

I'm starting to move my dragon fruit plants to planters that are up off the ground (the dogs have eaten some of the dragon fruit cuttings) and have soil that has been amended with the seaweed mix and biochar.

We just split an apple and it was delidious. I'm really ahppy to be getting good apples here in the subtropics. I don't know the variety. I bought it from a roadside seller several years ago.


Christiansted, VI(Zone 11)


Gadzooks. Five dogs.

Glad everything else is well and good.

I'd love some apple seeds, by the way, what could I have that you'd want to trade for?

I'm prezooming your minimum temps in the winter are 65F or higher... Apples?

There aren't any blackberries or blueberries? (Teehee, I know, not possible!) How about Black Raspberries!!!!


mulege, Mexico

I have a blueberry plant in a home made earth box and it's making new growth. I have more coming when my Argrostarts plants get to me. The earthboxes are great for them because I can add peat and special blueberry food. I'll be glad to send you some apple seeds.

Earlier this spring I was up to nine dogs. I have two good friends who help in the vet clinics done here during the winter by an American vet (Mother Lorraine) and they found homes for three of them. Then one got hit by a car. One who went to a new home in the country near here came back the next day. His new owners were frantic as they had already fallen in love with him. He had a homecooked meal and slept over and one of the clinic helpers returned him to his new home. He hasn't come back. I guess he wanted to say goodbye properly.

I saw a place in FL. that has Mysore raspberries which would maybe grow here but it was the cost of the plants plus a $55 certificate. Not this year.

Our minimum temperatures are above freezing. Occasionally someone more inland gets a frost but I'm right on the Sea so I get a definate winter season but no freezes.

One of my two cashew nut trees is blooming. Both trees are putting out new leafy growth.

I have two more truckloads of seaweed.

I keep reading the stuff on the Net about new fruits. The University of Florida is turning out lots of new fruit with low chill requirements.

Christiansted, VI(Zone 11)

None of the cashews in the neighborhood are setting fruit. They're all blooming, but no fruit. Pffft

mulege, Mexico

I'm not expecting fruit but since the tree is only one year old I'm pleased.

Responding to the mosquito problem, I'd only made extract in a five-gallon bucket with a tight lid. I don't know what kind of chemicals the dunks have in them. Using EM cuts down a lot of bug problems; I especially use it in the tanks that have fish waste.


Christiansted, VI(Zone 11)

EM, microbes, actually are the providers of food to plants. Plants don't eat nitrogen, potash, potassium, these are eaten by microbes, and microbe's poop is plant food.


mulege, Mexico

That's the way I understand it.


San Diego, CA(Zone 10b)

Nice thread!

I just came from the beach with a bag full of seaweed. I don't have a compost pile. Can I just chop it off and add to the soil as ammendement, or do I need to dry it up first?


Keaau, HI

If you dry it and grind it, it is easy to turn into the soil. Although I have had good results by chopping it up, turning it into the soil, liming (calcium carbonate, dolomite, or both) the bed, then waiting a couple weeks and planting.

San Diego is nice and warm, so the seaweed should rot into the soil quickly!

Christiansted, VI(Zone 11)

OK, BIG PROBLEM!!! Oh, my. Are we talking true seaweed, or what I have, sea grass?

Akkk! I duck and hide into a tiny hole.

I have Turtle Grass, and Manatee grass.

Not Kelp or other real sea-weed.


Keaau, HI

Anything that grows in the ocean probably makes a good supplement for soil.

San Diego, CA(Zone 10b)

Thanks Metrosideros! i have left it to dry on the lawn, and I will chop it off tomorrow (I don't have a grinder). One question though, what is liming for?

noonamah, Australia

Years back I lived in a place where I used to get mangrove leaves. They're good as well. Again, just the salt content (NaCl) you have to watch.

Keaau, HI

Liming is to add calcium carbonate and / or magnesium carbonate to the soil. This helps with metabolism and speeds up decomposition rates.
Dolomite, Limestone, Chalk, Ground Reef, and Oyster Shell are some of the materials available for liming.

Dolomite is half calcium carbonate and half magnesium carbonate. Applying a mixture of dolomite and another liming material is beneficial as plants generally take up calcium and magnesium ions in a 3Ca to 1Mg ratio (most liming materials are basically calcium carbonate).

All living organisms need calcium. It is the backbone of every cell. Use liming materials to apply secondary macronutrients (Ca & Mg) rather than just to correct pH.

When your plants get more calcium, and you eat your plants, then you get more calcium!

San Diego, CA(Zone 10b)

Thank you for enlightening me!
I suspect (with the little I know) liming would not be a good idea in my case as it seems this would make my soil even more alkaline than it is (desert soil). Does that make sense?

noonamah, Australia

It's usually a good idea to test soil before doing anything to it that will alter pH. But you're right, desert soils often have high pH.

Christiansted, VI(Zone 11)

The soil here on St Croix is amazingly alkaline, also. Off the chart dark blue.

Keaau, HI

If a soil is too alkaline, calcium can be added in the form of gypsum.

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