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Seaweed For Lawns: Surprising Benefits Backed By Science

Seaweed For Lawns: Surprising Benefits Backed By Science

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Paul Brown

I’m always on the search for creative pet and kid-friendly solutions to improving my lawn. Liquid solutions containing seaweed kept coming up as a beneficial ingredient for lawn care. I couldn’t wrap my head around it. And so, I dove into study-mode and did a ton of research. What I found surprised me.

Is liquid seaweed good for lawns? Multiple academic publications have documented the benefits of seaweed for lawns. The benefits observed include increased turf root mass, improved seed establishment, and increased drought tolerance.

I’ll walk you through the findings of these studies and how they convinced me to begin including liquid seaweed in my lawn care routine.

Why Is Seaweed Good For Lawns?

As it turns out, seaweed is recognized and used as a natural biostimulant in turfgrass and agricultural management. It’s dense with beneficial plant growth-supporting nutrients and micronutrients.

A study conducted in 2005 found that the use of a liquid seaweed extract resulted in a noticeable increase in turf root mass compared to non-tested areas. It also noted increases in rootzone nitrate-nitrogen availability and the researchers suggested that seaweed may increase microbial activity within the soil (source).

The study was not conclusive and further testing was recommended but it highlights the potential benefits of this natural alternative to chemical lawn fertilizers.

The Benefits Of Seaweed As A Natural Biostimulant For Lawns

To really understand the potential benefits of seaweed, you have to understand its role as a biostimulant.

According to Iowa State University’s Extension and Outreach department, biostimulants stimulate plant growth and increase stress tolerance (such as drought or disease). They report that grasses treated with a biostimulant endure stress conditions better because they have established a better defense system as a result of the treatments (source).

The reason that seaweed is believed to be such a powerful and effective biostimulant is that it contains high levels of Cytokinins which essentially a natural plant hormone (source). It is essential to plant cell division and root formation during active growth.

In fact, Cytokinins actually help plantlife to heal and repair itself (source). Mowing, walking, drought, and other stressors can hinder your lawn’s ability to thrive. When adequate amounts of Cytokinins are available, your grass can revitalize itself following these stressors.

Natural Vs Chemical Fertilizers

Natural fertilizers such as seaweed help to enrich the soil and lawn without introducing dangerous chemicals.

There are chemical biostimulant products available and widely marketed. While they do offer at least some surface-level benefit, it is important to understand the overall impact that chemical fertilizers have on both your lawn and soil.

A natural fertilizer such as seaweed revitalizes the ingredients that occur naturally in nature but may be depleted in certain soils. As a result, the lifecycle of naturally microbial activity is revitalized.

This results in higher quality soil which translates into stronger, deeper root growth and increased stress tolerance of grasses.

Chemical fertilizers, by contrast, introduce unnatural elements into the soil. This risks further imbalance of the natural life cycle of beneficial microbes.

While treatment may result in an initial increase in grass growth or improved color from the infusion of the chemical fertilizer, the impeding of microbial activity in the soil will take its toll, eventually resulting in poor quality soil.

This translates into decreased stress tolerance, higher soil compaction, and weaker root growth of grasses.

The irony is that by harming the beneficial microbes that thrive in the soil, we actually end up having to use more chemical fertilizer to constantly replenish the essential nutrients that would have existed naturally as part of those tiny creatures’ lifecycles (source).

Longterm effect of natural vs chemical fertilizers on soil and lawn health.

Seaweed Is Beneficial To Lawns, But It’s Not Enough

While studies have demonstrated the benefits of seaweed for lawns, simply applying a liquid seaweed extract and calling it done isn’t enough to ensure a thriving lawn.

Remember that at its core, a healthy lawn is the result of healthy soil. It’s important to feed the soil an abundance of micronutrients and regularly replenish the beneficial ingredients that make your soil alive.

To the extent possible, try to use naturally occurring ingredients.

The Synergistic Effect Of Seaweed And Other Ingredients On Lawn Grasses

The problem with using liquid seaweed extract or any other enhancer as part of your lawn improvement strategy is that it can be difficult to understand and calculate how much of each naturally-occurring ingredient should be applied.

You see, when individual ingredients are combined, they can have a synergistic effect, enhancing and balancing the other’s natural benefits. This is also known as a cumulative effect (source).

Rather than applying a liquid seaweed extract and several other soil and lawn enhancers separately, it’s best to choose a carefully blended mix of beneficial ingredients that are designed to complement each other and provide a comprehensive natural lawn care solution.

How To Add The Benefits Of Seaweed To Your Lawn

Simple Grow Solutions offers a Seaweed and Humic Acid Blend (link to Amazon) that can be sprayed with a traditional garden hose mixer. It’s an inexpensive way to begin incorporating the benefits of seaweed into your lawn care.

I’ve recently taken interest in a personalized lawn care solution offered by Sunday. In addition to seaweed, Sunday incorporates vital minerals and nutrients from food waste, iron, and molasses, as well as ensuring essential plant growth nutrients such as potassium and phosphorus.

Click here to read my complete review.

Developed by a scientist with a Ph.D. in turf science (yes, you can actually get a doctorate in grass!), Sunday customizes a seasonal fertilization plan for its customers based on the geographic soil and turf conditions and a personalized soil test that ensures you are addressing soil deficiencies and needs specific to your lawn.

I know of no other company that does this!

Instead of mixing and matching chemical fertilizers and wondering if I have enough of this nutrient or too much of another, I can simply spray the premixed solution onto my lawn using the handy sprayer packets that they provide and know that I’m giving my grass and soil what they need to thrive.

Basically, you pay for an annual plan, and then every couple of months or so they send you a custom pack with special blended solutions specific to your lawn’s needs throughout the growing season.

Go to their website and get more information. (Link to Sunday’s website).

Sunday lawn fertilizer plan includes seaweed and other natural grass and soil enhancers.
My initial Sunday lawn fertilizer pack


Seaweed for lawns is not a new concept but its gaining popularity as homeowners seek out chemical-free alternatives that are kid and pet-friendly.

As we grow increasingly aware of the compounding effect that chemicals have on our health, it’s wise to consider natural solutions when possible.

Remember that the health of your soil will ultimately dictate the health of your lawn. If you are dealing with heavily compacted soils like clay, have a look at our recommended compacted soil solutions.

To better understand why soil plays such an important role in the health of your lawn, read our comprehensive article What is Soil (And Why Does It Matter?)