How to Use Seaweed to Increase Cannabis Yields?

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Added 09 December 2022

When growing cannabis outdoors, we are particular about preventing weed growth around our precious plant. But did you know that there is one weed that can benefit your weed (pun intended)? 

We are talking about seaweed — an aquatic lifeform that offers tremendous benefits for cannabis plants and is packed with vital nutrients. Learn all about using seaweed fertilizer for cannabis in this article. 

What is Seaweed?

What is Seaweed?

Seaweed is aquatic algae — non-vascular plant life that ranges from red, and green to brown in color. Since this type of lifeform is non-vascular, it cannot transport nutrients around in its body; instead, it absorbs everything it needs directly from the water. 

Seaweed ranges in size from very minute forms to large sizes. In fact, the Antarctic kelp (a form of seaweed) can be as gigantic as 33 meters in length. Apart from color, each species of seaweed has a different composition, flavor, and nutritional value. And most often, seaweed is anchored to the ocean floor, but you can also find a few species that just float around in the water. 

But its nutritional value is what we need when growing cannabis. You can't undermine the benefits of seaweed for cannabsi cultivation. Learn more about it in the following section.

How Does Seaweed Benefit Cannabis?

How Does Seaweed Benefit Cannabis?

Most species of seaweed are rich in nutrients that can help your plant grow healthy and return better yields than ever. Some of the common nutrients found in seaweed include sulfur, boron, magnesium, calcium, and nitrogen along with various bioactive compounds like amino acids, lipids, proteins, and carbs — all of which are crucial for a cannabis plant’s health.

Additionally, most seaweed species are rich in vitamins A, B12, C, K, and E. 

Thanks to this, you can use seaweed as a terrific fertilizer for your cannabis plant, delivering a massive dose of nutrients and compounds, which make your plant grow taller and better. 

Plus, you can use seaweed as mulch by adding it to the topsoil. Doing so will trap moisture in the medium, so you don’t have to water the plant too often just to keep the roots moist. When used as mulch, seaweed can also prevent other weeds from taking root in your garden, which is particularly useful if you are growing cannabis outdoors

Seaweed also has some antimicrobial abilities, so it can also prevent pathogens like bacteria, parasites, or fungi from attacking your plant. For this benefit, you must use seaweed as a foliar spray to cover the plant in its antimicrobial goodness. 

Is Seaweed Safe for Cannabis?

We wouldn’t recommend seaweed unless it was safe, but like any other supplement or fertilizer, seaweed may still be dangerous for your plant if you overuse it. 

Remember, seaweed is dense in nutrients, so if you use too much of it to give your plant the highest levels of nutrients, it can backfire and cause a nutrient burn in your plant, especially in young plants, which can not only slow the growth but also affect the yield. 

It is crucial that you follow the right steps and only administer the right quantities when using seaweed on cannabis.

On the other hand, there’s a chance seaweed might be dangerous for you — legally. In many countries, it is illegal to harvest seaweed and it can be difficult to get a hold of it if you live far from the coast. This is because algae absorb more carbon dioxide than trees, playing a massive role in reversing the effects of global warming. 

How is Kelp Different from Seaweed?

How is Kelp Different from Seaweed?

The answer is — it’s not different at all. Kelp is just a type of seaweed, and is considered to be the best seaweed fertilizer for cannabis. It is rich in everything that your cannabis plant needs to grow healthy. Plus, it can help maintain the soil’s pH level. 

Kelp forms in kelp forests that are generally located in shallow waters rich in nutrients. Due to its anchoring location, it absorbs a ton of ocean minerals, which then benefit your cannabis plant. 

Kelp contains over 60 trace elements such as iron, cobalt, manganese, zinc, and molybdenum. 

So, kelp is not different from seaweed. In fact, if you go to purchase seaweed at your local gardening store, you will likely return with a kelp — that’s how common it is. 

Types of Kelp Products for Cannabis

Types of Kelp Products for Cannabis

Kelp (or any other seaweed) is available in various forms, each of which has its own benefits and downsides. Here are the best types of kelp products for cannabis:

1. Kelp Liquid

Kelp liquid is easy to use and the most accessible type of seaweed fertilizer, making it ideal for novice growers. It needs to be added to the water instead of soil, but when you water your plant, it reaches the roots quickly and benefits your plant.

2. Kelp Powder

Kelp powder is another type of product that can be added to water, but instead of watering your plant, you need to use kelp powder as a foliar spray. This is a quick way to feed nutrients to your plant but is generally recommended only when your plant is suffering from a deficiency and needs a quick nutrient boost. 

3. Kelp Meal

On the other hand, kelp meal is what you can add to the soil in advance. Over time, this seaweed fertilizer breaks down, providing a solid base of nutrients for your cannabis plant throughout its life cycle. However, it is crucial that you plan your growth so it starts breaking down at the right time.

Do You Need to Forage Seaweed for Cannabis?

Do You Need to Forage Seaweed for Cannabis?

Not always. You can forage it at your local beach, but if you don’t want to go through the trouble, you can simply buy it from your local gardening store. However, this can be a little difficult to find if you live far from the coast. 

Store-bought seaweed fertilizers for cannabis are easy to use and come with specific instructions, allowing even a novice grower to benefit from them. But you need to purchase high-quality seaweed products, failing which the benefits may not be so noticeable. 

Alternatively, if you don’t mind a day at the beachside, you can forage seaweed. Just find out where kelp (or seaweed) grows near your home — generally, it should be on shallow shores, so you can easily walk and harvest them. You can also walk along the beach and look for any washed-up seaweed. 

Identifying seaweed is difficult, so you need to narrow down a few common seaweeds you can find on your local coast. And if you are specifically looking for kelp, it is flat, broad, and long, and when it’s wet, it is soft and slimy. 

Lastly, you need to check your local laws regarding harvesting or foraging seaweed as it is illegal in many regions.

How to Use Seaweed for Cannabis?

The use of seaweed depends on whether you have bought seaweed from a store or foraged it yourself. Here is how to use seaweed for cannabis.

Store-bought Seaweed 

Store-bought seaweed and kelp products are relatively easy to use — they come with specific instructions, especially high-quality ones. So follow the instructions and you are good to go.

But if you are growing an autoflowering cannabis, you need to cut the amount by as much as three-quarters so your plant does not experience a nutrient burn. 

In most cases, if you are using liquid seaweed, you would need to add it to water and water your plant as usual. But if your product does not come with instructions, you can mix 1 teaspoon in 2.5 liters of water. 

On the other hand, for kelp meals, you need to at it to the soil at 0.5 kg per 9 cubic meter volume four months before you plant your seedlings.

For powder seaweed, you need to only add half a teaspoon to 5 liters of water and use it as a foliar spray. That’s it. 

Forage Seaweed

But if you have foraged seaweed, you need to use it in a different manner than mentioned above. Here are three ways to use foraged seaweed fertilizer for cannabis:

  1. The easiest method is to use it as mulch — place some seaweed on the topsoil surrounding your plant and let it degrade naturally 
  2. Add foraged seaweed to compost; the nutrients will be released into the compost in a while
  3. Leave seaweed in a bucket of water until it entirely breaks down, and then use it as a foliar spray for your plant

Summary: How to Use Seaweed to Increase Cannabis Yields?

Using seaweed is relatively easy. It may require more effort if you forage it, but it’s nothing you can’t handle. But this effort can go a long way in benefiting your cannabis plant. 

That said, there are no studies to prove the effectiveness of using seaweed fertilizer for cannabis. Thus, you should rely on your own tests when using seaweed to boost cannabis yields. You can also use seaweed extract for marijuana plants if you're so inclined. Seaweed and cannabis growth is closely related, and you'll perhaps notice this in a short period of time. 

Thanks to seaweed, your cannabis plant can get all the nutrients it needs to grow full and healthy, and in return, it will grow big, bushy buds in greater quantities — better yield than before. Using seaweed as a natural cannabis yield enhancer isn't new. So, if you want to enjoy such benefits, along with antimicrobial advantages, you should consider using seaweed for cannabis. 


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