Home-made Kelp Fertilizer

Make your own kelp fertilizer

Our compost pile consists of kitchen and garden wastes. Sometimes the wildlife and at other times the neighborhood dogs spread it around for us. 😉

Ray and I have been composting for several years now.  We throw all of our fruit and vegetable waste into the pile, along with tea bags, coffee grounds and washed egg shells, then turn it once a week or so.  Other than the egg shells, we had to stop putting any type of animal product (old cheese, unwashed egg shells, expired milk, etc.) into our compost pile because the local wildlife and some of the neighborhood dogs were attracted to it, and they would spread the compost from here to there, making a terrible mess.  Even so, we still got good compost!  But, let me explain why we don’t want to rely on our compost as our only soil amendment, and decided to make natural kelp fertilizer.

Before I go any further, here’s a little vocabulary to know:

Macronutrient:  an element required in large amounts for plant growth and development, consisting of nitrogen, potassium, phosphorous, calcium and magnesium.

Micronutrient:  an element or substance required in small amounts for normal growth and development of living organisms, including iron, copper, iodine and zinc. There are actually many more micronutrients than macronutrients.

Monoculture:  planting the same crop year after year, usually in large plots of land.

Make Your Own Kelp Fertilizer

Monoculture: where one crop is grown year after year on the same large acreage.


One of the biggest problems with monoculture  is that many of the micronutrients that we (humans) require are well used up from the soil after just a few years. Nitrogen, phosphorous and potassium, are added back to the soil by farmers, but what about selenium, copper, magnesium and cobalt? Generally, these micronutrients are not added back to the depleted soil, which means the resulting food produced on this land will not have these essential micronutrients.  Soils depleted of micronutrients is one reason why many of our foods available at the supermarket are not as nutritious as foods offered just one hundred, or even fifty years ago!

In the compost pile we can easily take care of a plant’s need for macronutrients.  Nitrogen, which promotes leaf growth, can be provided by chicken manure.  Potassium, which aids in flower and fruit development, can easily be added to the compost in the form of wood ash, which also adds calcium.  Phosphorous stimulates root growth and can be obtained from bone meal or bone char (burned bone meal).

But what about the micronutrients?  Where are they going to come from?  If a lot of the fruits and vegetables you purchase at the grocery store are lacking (monoculture) in micronutrients, therefore throwing your apple cores, squash peels and moldy carrot tops aren’t going to magically add these micronutrients.

Of course, you could always use a fertilizer that you purchase ($$$$$) containing a lot of the micronutrients that may be lacking in your soil.  Or, you can make kelp fertilizer!

Why kelp fertilizer?

Because, unlike soil that generally sits in one place and can be lacking this nutrient or that, our oceans are constantly circulating water (that carries micronutrients) all over our earth, and therefore the plants that grow in the ocean (kelp/seaweed) have more nutrients available for them to take in!

Kelp only has a small percentage of potassium, so it’s not a primary fertilizer of macronutrients, therefore it must be added in conjunction with other fertilizers, such as the aforementioned chicken poop, wood ash and bone meal!  Better yet, the nutrients in kelp are held in organic molecules, which is a form readily available to plants.

Another benefit of Kelp fertilizer is that it contains cytokinins, gibberellins and auxins, all valuable plant hormones. Studies show that cytokinins play a vital roll in cell division and enlargement and gibberellins aid in stem elongation, germination, and flowering.Make Your Own Kelp Fertilizer

So, last September Ray and I vacationed on the Pacific Coast and harvested an ice chest full of kelp.  We got lots of Bull Kelp, Kombu, Porphyra (nori) and Bladderwrack. According to Superfoods for Superhealth, in California we can harvest 17 pounds of seaweed/kelp per day from most public beaches!

DIY Kelp FertilizerOnce home, the seaweed was soaked in fresh water for about an hour, drained, then soaked in more fresh water.  This was to help remove the salt, sand and any little critters from the seaweed.  The seaweed was then placed in a large barrel with more fresh water and left to soak overnight.  Through the process of osmosis, a lot of the salt in the tissues of the seaweed are extracted into the fresh water.  That water was dumped and more fresh water was added – just enough to cover.  Now it was time to brew up some fertilizer!  A screen was placed over the barrel, and it was left in the hot sun to start fermenting.

how to make kelp fertilizer

Our ice chest full of kelp/seaweed.

The brew had to be stirred at least once a day.  Twice is best.

Boy, did it ferment!  The first few days everything seemed to be going well.  When I took the lid off the brew smelled like the beach the seaweed was taken from.  A little sour and musty, but nothing extreme.  There were a few flies trying to get into the brew, but I was able to fend them off.  That was until about the fourth or fifth day…

Peeeeeee yooooouuuuuu!

Let me tell you, this stuff gets stinky!  By two weeks we were wondering if the smell could get any worse!  Every time I went to stir the concoction, my eyes would water because it smelled so bad.  If I could describe it to you, it smelled like, well, hmmmm….

… actually, there really isn’t a description for the smell.  Just take my word for it, it’s stinky smelly!  If you decide to make your own kelp fertilizer, don’t say I didn’t warn you!  I could smell the fermenting sea juice at least 25 feet away.  50 feet if I was down-wind!Diy Kelp fertilizer

After a month, I could see that the kelp was breaking down into a stinky, almost gelatinous brew.  While I was stirring, I would always think of my high school days reading Macbeth…

“Double, double, toil and trouble;
Fire burn and cauldron bubble.”
After a couple of months the brew wasn’t quite as stinky.  Either that or my nose was just starting to get used to it! 😉  Apparently, the fertilizer is ready when it is no longer stinky, but instead smelled like a fresh summer day on the ocean.  So, I wasn’t quite there yet.
Now that we were into November and with the cooler days, the fermentation process was slowing down.  No matter, at least I wasn’t afraid of what the neighbors were thinking anymore!

But then Thanksgiving was just around the corner and Christmas shopping had to be done. Between birthdays and holiday festivities, I forgot to stir the goop every day.

How to make your own seaweed fertilizer

Looking into the barrel, you can see the fermenting, gelatinous and stinky, very stinky kelp!

A few weeks later, when I remembered, I noticed the smell wasn’t noxious anymore!  I’m not sure I could describe it as a fresh summer day on the ocean, more like soured jasmine flowers, but I believe the fertilizer was finally ready for bottling!  Hooray!!  At that point I fished out most of the remaining solid pieces of kelp, and added it to the compost pile, but I thought I should let it sit for another day or so to let any other solids float to the bottom before I used the spigot to bottle my liquid gold.
Then we went away for a week and came back to this:DIY Kelp fertilizer
And this:How to make kelp fertilizer
And this:Make Your Own Kelp Fertilizer
A bear had visited our homestead and tipped over my precious barrel of fertilizer!
Yes.  I did say some “not-very-nice” words such as #$%& and &@$#%!   After all that work! Waaaaaaaa….
Instructions on making your own seaweed fertilizerI was able to save a little more than 1/2 gallon of my precious fertilizer.  The good news is that the kelp fertilizer is to be diluted 15:1, so I actually have quite a bit of fertilizer left to add around my plants.  And as a foliar spray it should be used 20:1.  That was the good news.  The better news?  My dear husband suggested we go for another vacation to the coast to get some more kelp!
Yes, please!




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21 thoughts on “Home-made Kelp Fertilizer

  1. Hello Vickie.
    the with the compost is a great thing.
    We do this with us, but only to fruit which no citrus are.
    Otherwise, vegetables, tea and coffee grounds, etc.
    Best regards

  2. Ugh! It’s sure a good thing bears are cute (like raccoons) because they are such a nuisance. It’s not like they come in and eat an apple and leave, oh no. They treat every place like the community bachelor pad. Darn them:) Glad you were able to save some.

    • I know, right! When we first saw this bear a few years ago, it was this little cinnamon colored cub running through our new orchard. Now that stinker did something that was not funny! However, if you look at the picture of the BBQ that was tipped over, you can see an aerosol can (grill cleaner) on the ground next to the BBQ. It had one big tooth puncture in it and was empty. When Ray and I saw that, we could only imagine what a surprise that bear got when he chomped into the can! 😉 Probably our best assurance he won’t be back anytime soon!

    • Since I don’t have any “girls” yet, I would LOVE to have some chicken poop! Just not sure the USPS would be very happy with that 😉 Yes – I guess that’s just one of the hazards of living in the mountains, but I wouldn’t trade it for anything! Well, maybe a large estate in the Caribbean.

  3. I really want to make my own fertilizer. But, right now I live in an apartment, and I don’t really have anything to fertilize. Haha! When I was younger, my mom made fertilizer in our backyard in a giant fenced in area. She kept all the scraps like you said and she even went to pick up horse manure from a friend’s house every so often. I love the idea of kelp fertilizer! I’m pinning this to refer back to when I have a yard/garden that I can fertilize. Thanks so much for explaining all of the details and all of the photos! They’re so helpful! 😀

    • Hello, Gina! I’m glad you pinned this one for future reference, because kelp fertilizer really is easy to make and SO much cheaper than buying! Just remember – it gets really (seriously, really) stinky for the first few weeks! Thanks for stopping by!

  4. Darn that bear!! I have not made my own fertilizer, but I know that it is fabulous. Thanks for sharing with SYC.

    • Thanks, Jann! I haven’t actually seen the bear this year as he has been quite elusive, probably because of the neighbor’s dog. But, I know he’s around! Thanks for hosting!

  5. oh man do i see some bear proofing happening in the future? So glad you were able to save some of your trouble brew and will get to start a new batch (after the vacation!). You guys always have such excitement to share over there!

    • Never a dull moment! Sometimes I wish I could have boring day 😉 But, it keeps me thinking and moving and that’s what life is all about… right? We actually went back to the Pacific Ocean (Northern California Coast) last week and, believe it or not, the beaches were bare of kelp! We thought there would be lots of the stuff all over the place because we have had some fairly hefty storms this past few weeks. Nope. Oh well, I guess we will just have to go back!

  6. Oh boy, I would have been so irritated at that darned bear!!! After all that stinky, stinky work – and then one visit from a nuisance bear and it’s all gone!! Thankfully all my bears seem to be hibernating at the moment but they love to come around and cause trouble in the warmer months as well. I have stopped using fish emulsion because it draws them in which is a shame as I did like the results!

    • Yes, it truly was stinky, stinky! Luckily I was able to save 1/2 gallon of that precious fertilizer. Unfortunately, the bears in our area don’t hibernate all winter long. Here in Northern California, though we are in the mountains at 3,000 feet, it’s not unusual to have 50-60 degree days in the dead of winter! Thanks for commenting, Debbie!

  7. Wow, this was very interesting (and yet very depressing about the bear!!!!)… but I guess we will let bygones be bygones and just HAVE to make another trip to the beach. Sigh. But really, thank you for sharing this. I learned something new today. Never knew about the kelp fermentation process and its wonderful use! Thank you for sharing this on the Art of Home-Making Mondays! And if that line “double double” isn’t still stuck in my head from many moons ago too!!!

    • Belated greetings, JES! Sorry – I’ve been away from blogging for a few weeks. It’s true, we have let bygones be simply because you can’t cry over spilt fermented kelp, right?! Ah well – the reservations have already been made for our next coastal visit!

  8. I came here from Liz at Eight Acres, after reading her interview with you about the bees and have SO enjoyed reading a LOT of your older posts – learning a whole lot and being very inspired! So many new things to try on my list, making pectin (lots of crab apples up here that aren’t good for much, but probably good for that), lard, etc. Have added you to bloglovin’ and excited to keep following your journey. You may want to update your About page though!!

    • Good evening, Annet! So sorry this reply took so long. If you read my most recent post, you will understand why I have been absent for so long. I have read that crab apples make excellent pectin. But I also have read they make good, tart, hard cider! 🙂 Thanks for adding me and for the nice compliment. I am glad to get back to blogging again.