Five Reasons Why Using Seaweed Fertilizer Benefits Your Plants

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Using seaweed on your plants may sound a little strange, but in reality, seaweed and kelp fertilizers are well-known to many plant growers. These additives have a number of benefits for plants. For example, if your orchid’s growth has stalled, adding seaweed fertilizer to your feeding regimen could supercharge orchid root growth.

Seaweed and kelp extract are often used as nutrient supplements for plants, including orchids. Among other things, the vitamins and nutrients found in seaweed and kelp can help accelerate plant growth and support their health.

Healthy plants growing after seaweed fertilizer used

If you haven’t heard of seaweed or kelp fertilizer before, you’ve come to the right place. These are what I would call “next level” fertilizers. People tend to incorporate these types of fertilizers into their plant care once they’ve mastered the basic fertilizers like Miracle-Gro.

In this article, I’ll go over what seaweed fertilizers are. You’ll also learn more about the top seaweed fertilizer benefits and how you can use them to supercharge your plants’ growth. Lastly, I’ll give you some recommendations of several popular seaweed and kelp fertilizers along with links to buy them. Keep reading to learn more.

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What Is Seaweed Fertilizer?

Seaweed in the ocean, backlit by the sun above the water

In a nutshell, seaweed fertilizer is a nutritional supplement used to support plant growth. It is a broad term that includes fertilizers made out of seaweed extract, kelp extract, or liquid kelp. In reality, there are many different types and brands of seaweed fertilizer available out on the market.

Just to be clear, seaweed fertilizers are not actual stand-alone fertilizers, but are additives and supplements meant to be used in conjunction with regular fertilizers. In other words, you will still need to use a balanced NPK fertilizer such as Jack’s Classic All-Purpose Fertilizer to feed your plants.

For simplicity’s sake, I’ll refer to seaweed and kelp extracts as “seaweed fertilizers” from here on out. However, just know that they are not true fertilizers and they work more like supplements to be used alongside regular NPK fertilizers.

Kelp Vs. Seaweed Fertilizer For Orchids

Throughout this article, I will be talking about seaweed fertilizer benefits. However, please be aware that when I do this, I am also including kelp fertilizer in this umbrella term. They are similar, but not the same product.

What Is The Difference Between Kelp And Seaweed?

Before we get into the benefits of seaweed fertilizer, we should distinguish the difference between seaweed and kelp.

Seaweed is an umbrella term that refers to many different types of marine-based algae and other plants, including kelp.

Kelp is a type of seaweed, but is a more specific term that refers to the large brown algae classified as Laminaria. Kelp is popular because it is also an edible form of seaweed. You may know of it as kombu, which is used in a number of Japanese dishes.

Which Is The Better Choice For Orchids?

When trying to decide which is more beneficial to orchids, kelp vs. seaweed, the answer is neither one is better than the other. Both kelp and seaweed fertilizers have similar benefits. I’ll go into more details about this next.

Five Seaweed Fertilizer Benefits

Plant growing outdoors after being watered with seaweed fertilizer

There are several compelling reasons why you should incorporate seaweed or kelp fertilizer into your orchid’s feeding regimen. Since this is an orchid site, I’ll mostly focus on benefits to orchids here. However, please know that you will likely see these same benefits in all types of plants.

Seaweed Fertilizer Benefits: Accelerates Root Growth In Orchids

One of the biggest benefits of seaweed fertilizer is that it supercharges root growth in plants. This is true for all plants, not just orchids.

Once you start using seaweed or kelp fertilizer, you should start seeing increased root growth within a few weeks. This may be in the form of more root buds, new roots branching off of old roots, or accelerated growth of existing roots. This is especially important if you are looking to save an orchid without roots or help an orchid suffering from root rot.

For best results, you will need to apply seaweed fertilizer during the orchid’s active growth phase. An orchid’s growth phase is when the orchid is actively forming new leaves and roots. It is generally the best time to increase fertilization and add supplemental nutrition for your orchids.

The growth phase usually happens after the flowers have fallen off. Depending on the species, the orchid may enter a brief dormant period after losing its flowers or it may jump straight into the growth phase.

To learn more, check out this guide to the different phases of an orchid’s growth and life cycle and how to fertilize an orchid.

Rooting Hormones And Growth Hormones

So, how does seaweed fertilizer help with root growth in plants, including orchids? The answer is rooting hormones. As I discussed in my rooting hormone article on Everyday Orchids, rooting hormone helps stimulate root growth in all plants.

Many types of seaweed and kelp contain rooting hormones in the form of auxin. Auxin is a plant hormone that helps stimulate root growth and formation of root buds.

When orchids and plants are exposed to increased levels of auxin through the seaweed fertilizer, they will start to grow new roots or show accelerated growth of existing roots.

The presence of auxin also stimulates the plant’s root tips to release cytokinin, a plant growth hormone. Cytokinin triggers more cell growth and division. This is important in leaf formation and above-the-ground growth.

In short, more roots lead to more growth overall. The more roots an orchid has, the more ways it has to uptake water and nutrients. It will then be able to grow more leaves and flower spikes. In short, regularly using seaweed fertilizer will result in a healthier plant.

Seaweed Fertilizer Benefits: Use It To Save Rootless Orchids

Another one of the major seaweed fertilizer benefits is that it can be used to reroot orchids. Yes, even those orchids who have lost all their roots to rot or disease can be saved.

This is due in large part to the seaweed fertilizers’ growth hormones and its powerful rooting effect.

To save an orchid without roots, simply turn the orchid upside down and spray the seaweed fertilizer on the underside of the leaves.

This is called “foliar feeding.” You can check out this guide to feeding orchids with a fertilizer mist spray for more information on how to foliar feed your plants.

In addition, please read about how to use seaweed fertilizer to feed plants. You’ll learn how to prepare and use seaweed and kelp fertilizer on orchids and other plants.

Seaweed Fertilizer Benefits: Provides Powerful Nutrients

A third benefit that seaweed fertilizer provides plants is that it is full of nutrients. Both seaweed and kelp fertilizers contain many different vitamins and nutrients that can support plant growth.

Seaweed, for example, contains vitamin A, B6, C, D, antioxidants, and omega-3.

Kelp is even richer in nutrients, containing vitamin A, B12, B6, magnesium, iron, calcium, zinc, and many other vitamins and minerals.

It is for this reason that kelp and seaweed are referred to as “superfoods.” To break it down for you, one of the biggest seaweed fertilizer benefits is that it is packed with nutrition for your orchids.

Seaweed fertilizers also contain small amounts of macro nutrients such as nitrogen, potassium and phosphorus. These are, coincidentally, key orchid fertilizer components. However, these macro nutrients are present in such small quantities that it is almost negligible. For this reason, your orchid will need a balanced orchid fertilizer in addition to seaweed fertilizer.

Seaweed Fertilizer Benefits: Keeps Leaves Green And Roots Healthy

Another one of the top seaweed fertilizer benefits is that it supports leaf and root health. This is due to all the rich nutrients found in seaweed mentioned above.

Regular use of seaweed fertilizer to feed your plants and orchids results in brighter, greener leaves. You’ll also notice that your orchid roots are thicker and healthier looking.

Seaweed Fertilizer Benefits: Will Not Burn Leaves Or Roots

A fifth benefit of seaweed fertilizer is that it is gentle on plants. Most seaweed fertilizer products are organic and don’t contain added chemicals or preservatives. Unlike traditional orchid fertilizers, whose fertilizer salts may lead to root burn, seaweed fertilizers do not burn leaves or roots.

You can apply seaweed fertilizer as a foliar spray on your garden vegetables and orchids. You can also soak your orchid roots in a seaweed fertilizer solution or apply this to your other plants without fear of damaging the plant.

Bonus Benefit: Relatively Inexpensive

This is not exactly a benefit for your plants, but it is an added bonus for you. Seaweed fertilizer is relatively inexpensive when you consider how little you need per feeding and how you can stretch out one bottle over months.

Bottles of seaweed fertilizer are typically sold as concentrated solutions. Thus, you will need to dilute the seaweed fertilizer in water before using it.

Depending on how much seaweed fertilizer solution you are making, you will need anywhere from 1/4 teaspoon to 1 Tablespoon of seaweed fertilizer at a time.

As you can see, a little bit goes a long way. A bottle of seaweed or kelp fertilizer can last you a long time.

In addition, since it is an additive and not an actual fertilizer, you will not be using it each week. Instead, you will only be using seaweed fertilizer on your plants once or twice a month. For more information, check out this guide on how to use seaweed and kelp fertilizers on your plants.

When spread out over time, the cost of a seaweed or kelp fertilizer is relatively low, especially when you consider all the benefits you are providing to your orchid each time you use it.

Best Seaweed Fertilizers

Person pouring seaweed fertilizer into measuring cup

With so many different products out on the market, you may be wondering which one you should buy. Below, I’ll give you some suggestions for popular seaweed and kelp fertilizers used by orchid growers.

Note: Many of these seaweed fertilizer products can also be used on other indoor and outdoor plants besides orchids.

With the exception of Orchid Love, none of these products are specific to orchids. All products listed below are safe for use on all plants.

Clean Kelp

Clean Kelp is an organic seaweed and kelp fertilizer supplement, made by Bloom City. It comes in a concentrated, 32-ounce bottle. Clean Kelp is a blend of 7 different species of kelp and seaweed and is safe for all plants, including orchids.

Prepare this for use by mixing 1 teaspoon of Clean Kelp in 1 gallon of water. For foliar feeding, use just 20ml of Clean Kelp per gallon of water.

Liquid Seaweed For Plants

Liquid Seaweed For Plants, by Blue Planet Nutrients is another great product. It is made from Ascophyllum Nodosum seaweed. This product comes concentrated in a 32-ounce bottle and can be used on all types of plants.

You can use it in hydroponic settings and for orchids potted in moss, coconut coir or other types of soil-less media.

MaxiCrop Liquid Seaweed

MaxiCrop Liquid Seaweed is a kelp extract by MaxiCrop. This product is a 100% pure seaweed extract, without any other additives or chemicals.

MaxiCrop Liquid Seaweed can help orchids grow vigorously, produce lots of blooms and grow plentiful roots. To dilute this, simply mix 1 capful of product in 1 gallon of water. You can also use this in hydroponic settings or as a fertilizer mist spray.

Sea Magic

Sea Magic is a dry, soluble seaweed extract powder. It comes in a highly concentrated 1-ounce package. To make the concentrated solution, you’ll need to dissolve the package contents into 1 gallon of water. Keep this in a cool, dry place.

Then, to prepare the seaweed fertilizer for use on your orchids and other plants, mix 1 Tablespoon of concentrated solution with 1 quart of water.

If you are feeding smaller orchids or want a smaller batch, use 1/4 teaspoon mixed in 1 pint of water. Feed your orchids every 2-3 weeks with this. It works well with any standard fertilizer.

Liquid Kelp Fertilizer

Liquid Kelp Fertilizer by GS Plant Foods is another popular seaweed product. You can use this with your regular NPK fertilizer to achieve better blooms and enhanced growth. This product can be used on your orchids, gardens and lawn. It doesn’t smell and can be used indoors.

Orchid Love

GS Plant Foods also sells Orchid Love, which is a more orchid-specific seaweed fertilizer. It contains liquid kelp, plant and rooting hormones and other nutrients to give your orchid the boost it needs.

Use this to get healthy green leaves, thick roots and improved growth on your orchids. It can also get your orchids to bloom and rebloom, year after year. It is sold as a concentrate, so you will need to dilute 1 Tablespoon in 1 quart of water prior to use.

You can safely use Orchid Love on both indoor and outdoor orchids.


KelpMax (not an affiliate) is another popular kelp extract used for feeding orchids. This product is made from Ecklonia Maxima kelp, which contains more growth hormones than other kelp.

It also contains a number of vitamins, minerals and other nutrients that are great for orchids and other plants. Generally, you will want to dilute 1 Tablespoon of KelpMax in 1 gallon of water and mix well.

Storing Seaweed Fertilizer

One thing to note is that some of these products do not have a long shelf life. I would aim to keep your open bottle of seaweed extract or kelp extract in the refrigerator and use it within a year. If you are unable to store it in your refrigerator, then store it in a cool, dry place.

As the product dries out or degrades over time, you will lose the effectiveness of the product. While your plants will still benefit from the vitamins and minerals left in the product, you won’t see the amazing growth you might be hoping for.

This is why I would recommend buying just what you think you will be able to use within a year. If you only grow orchids and houseplants, then a smaller bottle would be sufficient.

However, seaweed fertilizer can be used on all types of plants, including outdoor plants, houseplants, orchids, lawns and shrubbery. If you plan to use this on a larger scale, you may want to buy a larger gallon-size jug of seaweed fertilizer concentrate. This will give you a better price per ounce.

Final Thoughts

Seaweed fertilizers can be a great additive for your plants. As you have learned, one of the top seaweed fertilizer benefits is its ability to supercharge root growth. You can use this to save a sick orchid or one that has lost all its roots. Other seaweed fertilizer benefits include high levels of nutrients for your plants and a relatively low price once you divide the cost per use.

If you are unsure if seaweed fertilizer is right for your plants, I recommend you buy a small bottle initially. Start by using it once a month on your plants. You should see results within a few weeks.

Just remember that seaweed fertilizer won’t replace your plant’s regular fertilizer. It is meant to be given in addition to the NPK fertilizer you are already using. Seaweed fertilizers are full of nutrients and can be a great supplement used to support your orchid’s health. Give it a try and see!

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Pink spotted orchids outdoors in the sunlight
Healthy orchid in purple pot after being treated with seaweed fertilizer
Purple and white orchid flower
Healthy plants on bookshelf after being treated with seaweed fertilizer
Houseplants by window
Yellow and white Dendrobium orchid after getting seaweed fertilizer

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