Best Seaweed Fertilizer: Top 5 Picks

By Amod Khan

Updated on

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In recent years, more and more people are turning to seaweed fertilizers as a natural and super effective way to help plants grow better and keep the soil healthy

These fertilizers are packed with nutrients and have lots of benefits, which is why they’re becoming popular with gardeners, farmers, and folks who care about the environment.

As people become more aware of the impact traditional fertilizers can have on the environment, they’re looking for better, eco-friendly ways to help their plants grow. 

That’s where seaweed fertilizers come in! They’re getting a lot of attention because they offer so many great benefits.

In this guide, we’ll cover everything you need to understand about seaweed fertilizers. 

We’ll discuss the best seaweed fertilizer available, and provide a detailed guide on how to use them effectively.

We will also discuss step-by-step instructions, share DIY tips for creating your fertilizer, and ensure you understand how to use them safely.

List of Best Seaweed Fertilizers


1. Neptune’s Harvest Organic Hydrolized Fish & Seaweed Fertilizer

Neptune’s Harvest brings together the goodness of fish and seaweed to create a powerful organic fertilizer. 

Made from fish and seaweed found in the North Atlantic, this liquid fertilizer is packed with important nutrients, amino acids, and natural growth boosters.

It’s simple to use by spraying it on leaves or watering it into the soil, making it great for many plants. 

With lots of nutrients, this fertilizer helps plants grow strong and handle tough conditions better.

2.  Maxicrop Liquid Seaweed

Maxicrop is well-known for its seaweed products. Their liquid seaweed fertilizer comes from a type of seaweed called Ascophyllum nodosum, found in the North Atlantic. 

It’s a strong mix that can be used in soil or sprayed on leaves. 

Full of tiny minerals, vitamins, and growth helpers, it helps roots grow, takes in nutrients better, and makes plants grow strong and fast. 

It’s easy to use and works well with other fertilizers, which is why gardeners love it.

3. OrganicDews Liquid Seaweed Concentrate

This natural plant booster is made from powerful seaweed and is loved by organic gardeners. It helps plants grab nitrogen from the air and improves soil health.

It promotes better seed sprouting, stronger roots, and overall healthier plants.

4. Seagate Products Fish Fertilizer Concentrate With Seaweed:

Seagate Products brings you a one-of-a-kind blend of fish fertilizer and seaweed, harnessing the best from both marine and aquatic realms. 

Crafted from whole sardines and nutrient-rich seaweed, this fertilizer is packed with essential amino acids, proteins, and micronutrients.

What sets it apart is the gentle cold processing method employed, preserving the natural goodness of the ingredients. 

This means your plants get the full range of benefits they offer. With a well-balanced mix of nutrients, it promotes strong root development and vigorous plant growth.

5. Dr. Earth Premium Gold Organic Seaweed Concentrate:

You’ll appreciate Dr Earth’s seaweed concentrate if you care about the environment and love gardening. 

It’s made from Norwegian kelp that’s harvested sustainably, along with other natural ingredients.

This handy product can be used in different ways: you can pour it on the soil, spray it on leaves, or dip transplant roots in it. 

It’s packed with nutrients that help the soil’s tiny helpers thrive, boost plant growth, and keep your plants healthy. It’s the perfect pick for anyone who wants to garden organically.

Advantages of Using Seaweed Fertilizer

1. Rich in Nutrients: Seaweed fertilizer is packed with vital nutrients like nitrogen, potassium, phosphorus, and micronutrients, providing plants with a balanced diet for robust growth.

2. Improves Soil Health: The organic matter in seaweed enhances soil structure, boosts microbial activity, improves water retention, and enhances aeration, creating a healthy environment for plant roots to thrive.

3. Boosts Plant Growth: Seaweed contains natural growth hormones such as auxins, cytokinins, and gibberellins, which stimulate plant growth, foster root development, and promote stronger, healthier plants.

4. Increases Yield and Quality: Regular use of seaweed fertilizer can lead to higher crop yields, better fruit quality, increased flower production, and overall improved plant health.

5. Versatile: Seaweed fertilizer can be applied to various types of plants including vegetables, fruits, flowers, and ornamentals, making it a versatile choice for both gardeners and farmers.

6. Promotes Biological Activity: Seaweed fertilizer boosts beneficial microbial populations in the soil, crucial for nutrient cycling, organic matter decomposition, and disease suppression, resulting in healthier soil and plants.

7. Regulates Soil pH: Seaweed contains compounds that help regulate soil pH, ensuring optimal conditions for nutrient absorption and plant growth.

8. Safe and Natural: Seaweed fertilizer is natural, organic, and non-toxic, making it safe for children, pets, and beneficial insects, and causing minimal harm to the environment compared to synthetic alternatives.

How To Use Seaweed Fertilizers: A Simple Step-by-Step Guide

1. Select Your Preferred Type

Seaweed fertilizer is available in liquid, powder, or granular forms. Choose the one that suits you best and is easiest to work with.

2. Dilute Liquid Concentrates 

If you’ve opted for a liquid seaweed fertilizer, make sure to dilute it as per the instructions provided by the manufacturer. 

This usually involves mixing a specific quantity of the concentrate with water in a watering can or sprayer.

3. Prepare the Application 

No matter if you’re using liquid, powder, or dried seaweed, it’s important to get it ready for use. 

Simply follow the guidelines on the product packaging to ensure you get the right dilution ratio or method of application.

4. Apply to the soil

Before using the seaweed fertilizer, make sure to water the soil around your plants thoroughly. 

This helps the soil to absorb the nutrients better. Once the soil is moist, apply the seaweed fertilizer directly to the soil near the base of your plants. 

Be careful not to get the fertilizer on the leaves, as this could cause burns, particularly if using a concentrated solution.

5. Give your plants another drink

Once you’ve applied the seaweed fertilizer, give your plants a light watering. This helps the nutrients to seep into the soil and nourish the roots. 

Additionally, it helps prevent any potential buildup of salt on the soil surface.

6. Keep it up as required

Depending on the type of seaweed fertilizer you’re using and the requirements of your plants, you might need to apply it again every few weeks or months during the growing season. 

Just follow the guidelines provided by the manufacturer for how often you should use it.

7. Watch Your Plants’ Health

Keep a close watch on your plants to see how they’re reacting to the seaweed fertilizer. Look for signs like better growth, increased vitality, and healthier leaves. 

If needed, tweak your fertilization routine or amount based on what you observe.

8. Consider Foliar Application 

Apart from adding seaweed fertilizer to the soil, you can also spray it directly onto the leaves as a foliar application. 

Just dilute the fertilizer as directed and spray it onto your plants’ leaves. This can give them a rapid nutrient boost and might help them cope better with challenges like heat or disease.

9. Handle Storage Carefully

Follow the manufacturer’s guidelines to store any leftover seaweed fertilizer properly. Keeping it stored correctly ensures that the product maintains its quality and effectiveness for future use.

Following these easy steps will help you use seaweed fertilizers to encourage healthy growth and plentiful harvests in your garden.

Make Your Seaweed Fertilizer: DIY Tips


1. Gathering Seaweed

If you live near a beach or coastal area where seaweed is plentiful, you can collect it yourself. 

Make sure to choose seaweed that’s clean and not contaminated with pollutants. Also, check and follow any local rules about collecting seaweed.

2. Cleaning the Seaweed

After gathering the seaweed, give it a thorough rinse with fresh water. This step removes excess salt, sand, and other debris.

3. Cutting or Shredding

Next, chop or shred the rinsed seaweed into smaller pieces. This helps in breaking it down further and extracting nutrients effectively.

4. Soaking the Seaweed

Place the chopped seaweed into a container like a bucket or large jar, and cover it with water. 

Let it soak for several days to allow the nutrients from the seaweed to leach into the water. Stir the mixture occasionally to aid in the nutrient extraction process.

5. Separating the Liquid

Once the seaweed has soaked for several days, separate the liquid from the solid seaweed by pouring it through a fine mesh strainer or cheesecloth. 

The liquid you collect is your seaweed fertilizer.

6. Adjusting the Strength

Depending on how concentrated the seaweed fertilizer is, you might need to dilute it with water before applying it to your plants. 

A common ratio is mixing one part seaweed fertilizer with four parts water, but you can adjust this to suit your plants’ needs.

7. Using the Fertilizer

Apply the diluted seaweed fertilizer to your plants by watering the soil around their base or spraying it directly onto their leaves. 

This gentle fertilizer can be used regularly throughout the growing season to promote healthy growth.

8. Saving the Excess

Any leftover seaweed fertilizer can be stored in a sealed container in a cool, dark place for future use. 

Remember to label the container with the contents and the date you prepared it to keep track of its freshness.

By following these DIY steps, you can make your seaweed fertilizer to feed your plants and support their healthy growth in an eco-friendly and budget-friendly manner.

Precautions & Warnings

1. Don’t Go Overboard: While seaweed fertilizer is great for plants, using too much can hurt them. 

Stick to the recommended amounts to avoid messing up the balance of nutrients and causing harm.

2. Check for Allergies: Some people might be allergic to seaweed or the stuff in seaweed fertilizer. 

If you know you have allergies, it’s a good idea to wear gloves and other protective gear when handling it, just to be safe.

3. Stick to the Plan: Seaweed is full of good stuff for plants, but too much can be too much. Make sure you dilute it properly and don’t use it too often. It’s better to follow the instructions on the package.

4. Think About the Salt: Seaweed naturally has salt in it, which can be bad news for some plants if there’s too much. 

Be careful if your soil already has a lot of salt, or if you’re using other salty stuff in your garden.

5. Keep an Eye on Your Plants: Watch how your plants react to the seaweed fertilizer. If they start looking sad, like their leaves are burning or they’re drooping, you might need to ease up on the fertilizer.

6. Store it Right: Keep your seaweed fertilizer in a cool, dry spot away from the sun. Make sure the lid is on tight so it stays fresh and doesn’t get yucky.

7. Mixing with Other Stuff: Some fertilizers or bug killers might not play nicely with seaweed fertilizer. Unless the instructions say it’s okay, it’s probably best to keep them separate.

8. Think About the Environment: Even though seaweed fertilizer is pretty friendly to the planet, too much of it washing away into rivers and stuff can cause problems. 

Try to be careful with how much you use, and follow any rules about throwing away fertilizer.

9. Keep Away from Kids and Pets: Store your seaweed fertilizer where little hands and paws can’t reach it. We don’t want anyone accidentally eating or playing with it.

By following these simple tips, you can give your plants a boost with seaweed fertilizer without any worries.


In summary, using seaweed fertilizers is a great way to naturally help your plants grow better, make your soil healthier, and take care of the environment. 

When you use seaweed fertilizers in your gardening or farming, you’ll see your plants become stronger, get more crops, and help make the world a bit greener and healthier for everyone.


What is seaweed fertilizer best for?

Seaweed fertilizer is great for giving plants a boost of essential nutrients they need to grow strong and healthy.
It’s especially good for improving soil quality, helping plants resist stress, and promoting overall plant growth.

What is the NPK of seaweed?

Seaweed doesn’t have a fixed NPK ratio like synthetic fertilizers do. Instead, it contains a wide range of nutrients, including nitrogen (N), phosphorus (P), and potassium (K), as well as trace minerals and growth hormones.
The exact nutrient composition can vary depending on factors like the type of seaweed and how it’s processed.

Which plants like seaweed feed?

Many plants benefit from seaweed fertilizer, including vegetables, fruits, flowers, herbs, and even lawns. Seaweed provides a balanced mix of nutrients that support healthy growth and development in a wide variety of plants.

Is seaweed fertilizer good for all plants?

While seaweed fertilizer is generally beneficial for most plants, there are some exceptions.
Certain plants may be sensitive to the salt content in seaweed or may not respond well to the specific nutrients found in seaweed fertilizer.
It’s always a good idea to start with a small amount and observe how your plants react before applying seaweed fertilizer extensively.

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