How to Make Liquid Seaweed Fertilizer For Plants: DIY Guide

Have you heard the hype about seaweed fertilizer? Cultures have been using seaweed to fertilize crops for centuries, and surprisingly, so can you!

Whether you gather kelp from a beach near you or buy sheets of nori, this organic, nutrient-rich liquid is simple to make and only costs mere pennies. As a bonus, seaweed fertilizer has a mild smell that dissipates quickly, unlike its pungent counterpart, fish extract fertilizer.

It's time to learn how to make homemade seaweed fertilizer and ride the wave to a bigger, better harvest!

O-Fish-Ally Great Plant Food

Choosing the fertilizer that is right for your plants is difficult because every garden is unique. Plus, there are thousands of options out there, each with an ad campaign or online guru claiming this one is superior. 

The following blog posts will help you choose the best fertilizer for vegetable gardens based on facts and science! Each fertilizer on our list has been scientifically proven to be very effective and reliable, and thoroughly tried and tested in our own garden and farm over the last two decades.

• Trifecta Fertilizer

• How to Make Compost 

• How to Make Bone Meal Fertilizer 

• How to Make Compost Tea

• Vermicomposting

• How to Add Nitrogen to Soil

• Making Weed Tea Fertilizer: Does It Work & Is It Worth It?

What Is Seaweed Fertilizer

Seaweed fertilizer is just what it sounds like, plant food that contains seaweed or seaweed extract as the main ingredient. Seaweed is, hands down, the most micronutrient-packed material on Earth! This magical plant is growing in oceans, which make up the largest percentage of over all surface area of the Earth. 

What’s incredible is that the ocean is the world’s largest nutrient trap! All of the nutrients found on land get washed away, eventually they end up in the waterways, and all waterways lead to the ocean. 

Nature has no way of getting the nutrients back out of the water and on land because when water evaporates, it leaves the nutrients behind. The only way to get all those great nutrients back on land is through a plant that uptakes the nutrients and grows with them- seaweed! 

What Makes Seaweed Fertilizer So Great

Civilizations have been using seaweed of all types to grow with for centuries. In one little sheet of nori (edible dried seaweed), there is not only lots of nitrogen, but also phosphorus, potassium, and over 70 different trace minerals! That’s what I’m really going for—the trace minerals found in seaweed that are depleted in our modern day soils.

Besides being very inexpensive (it cost me about $1 to make this batch), seaweed fertilizer significantly improves nutrient use efficiency, crop yields and quality, and enhances soil. You don't have to just take my word for it, that information comes directly from a study by the National Library of Medicine on the effectiveness of seaweed fertilizer.

Supplies Needed

It’s a short list, and you might already have these supplies lying around the house:

• Nori - Buy unroasted and unseasoned nori or any other form of rinsed seaweed. On the back of the packaging, you want to check the sodium levels! If the sodium is less than 4%, it has been rinsed and can be used to make seaweed fertilizer. Pro-Tip: You can absolutely gather seaweed from the ocean yourself, but make sure that you rinse it very well! Sodium and salt are not good for your soil, even in moderate quantities.

• Water - This recipe requires about a gallon of water per batch. 

• Pint Mason Jar - One glass pint mason jar is all you need. Glass jars are great to use for DIY projects like this because they are completely non-porous and chemically inert. This means bacteria, odors, and stains cannot seep into the material.

• Watering Can - You will also need a one-gallon watering can.

How to Make Liquid Seaweed Fertilizer For Plants

To unlock the amazing micronutrient fertilizing powers of seaweed, all you have to do is follow these simple steps:

1. Fill Jar - Fill a pint jar with about 1 1/2 cups of water.

2. Crumble Seaweed - Take 3 sheets of the nori (dried seaweed), fold or crumble them, and put them into the pint jar of water.

3. Wait - Let the jar sit for one to three days while the seaweed absorbs water. The water will smell fishy and change colors. Don’t be alarmed if it changes to green, yellow, orange, brown, or even a pinkish purple like mine did. 

4. Dilute the Mixture - At this point, your pint jar of seaweed fertilizer is very, very potent! Pour it into a one-gallon watering can and fill the watering can the rest of the way with fresh water to dilute the fertilizer. Pro-Tip: You don’t have to dilute the fertilizer with a full gallon of water if you don’t want to. Heck, you could even apply it straight. It is gentle and won’t burn your plants, but the recommended dilution stretches it out to maximize the fertilizing power.
5. Apply to Garden - The fertilizer is ready to be used.

How to Apply Seaweed Fertilizer

This seaweed fertilizer recipe is safe enough that you can use it on absolutely anything, like house plants, garden vegetables, fruit trees, and ornamentals. I have been using it for years (even though I also fertilize with Trifecta+ and use compost) because I want the benefits from the micronutrients it has.

The best thing is that you really can’t go wrong with applying this fertilizer. It can be applied as a root drench and as a foliar feed. Root drenches are awesome; what they essentially do is supercharge the root system. A foliar feed is applied to the leaves because plants will also uptake nutrients through their leaves.