Friday, May 17, 2024

Seaweed: A Potent Superfood Fertilizer For Marijuana Plants

Seasoned cannabis growers know that seaweed is perhaps the best way to increase crop growth and boost the health of marijuana plants.

Seaweed is one of the healthiest and tastiest ingredients used in cuisines around the world. It’s a potent source of many nutrients, including iodine, B vitamins, vitamin K, iron, zinc, and even antioxidants; all of these offer tremendous health benefits for us. But did you know that seaweed is a potent superfood for your marijuana plants too?

In fact, seaweed has been used for agricultural purposes for centuries now. Since ancient times, people have been using seaweed to fertilize the soil and even make infertile soil, fertile. Research into the use of seaweed (as well as kelp) has boomed in modern times, proving the efficacy and usefulness of this humble weed to strengthen the growth of many crops, including marijuana.

Growing Marijuana
Photo by DaveLongMedia/Getty Images

What Is Kelp and Seaweed?

Seaweed, also known as macroalgae or algae, is an umbrella term that refers to thousands of species of plants that grow in water. They can be found in different bodies of water including the ocean, lakes, and even rivers. Some species are microscopic and thus can’t be seen with the human eye, but they still serve an important purpose in marine ecosystems by supporting the food chain.

RELATED: Rookie Errors To Avoid When You Are Just Starting To Grow Weed

Kelp is a popular type of seaweed. It’s a large kind of seaweed that commonly grows in sea forests. Many seaweed fertilizers are made from kelp or a combination of other seaweeds.

Seaweeds do not contain internal vessels that transport nutrients around them. Because of this, they are able to absorb everything from the water directly, which is why they need to stay in water in order to survive.

Benefits of Using Seaweed Fertilizers

While there are many tried and tested ways to grow healthy marijuana plants, adding seaweed fertilizer to the mix can make it even better. It’s certainly a much better alternative to conventional fertilizers, and it can help your plants thrive despite being exposed to environmental stress including disease, pests, salinity, and drought.

Seaweed is considered a biostimulant for cannabis and other plants. Biostimulants refer to natural products, not limited to fertilizer, which can help promote the growth of plants when given in small quantities. In agriculture, biostimulants have been used to assist with responsible and sustainable agriculture.

RELATED: What’s The Difference Between Sun Grown And Indoor Grown Marijuana?

Here’s why you should be adding seaweed as a superfood fertilizer for your cannabis plants:

  • Excellent nutrition: When seaweed grows in bodies of water, it absorbs many macronutrients, micronutrients, and minerals that it passes on to plants. No other fertilizer can match the nutrition profile of seaweed!

On top of the nutrients mentioned above, it also contains potassium, calcium, magnesium, boron, phytohormones, and fatty acids. When marijuana plants absorb these through fertilizer used, it gives them a serious nutrition boost that helps them grow and tolerate stress efficiently.

  • Improves moisture: When you add dry seaweed to the topsoil of cannabis in the same way you do with mulching, it’s an effective way to trap moisture within the soil. As a result, you will need to water less but you can have peace of mind that the cannabis roots are thriving.
  • Germination: Apply seaweed to marijuana plants will promote germination of seeds while also helping regulate the pH levels in the soil. In addition, it will improve marijuana metabolism when it increases the trace minerals within the soil so that the plants and roots can easily absorb the nutrients.
  • Fights bacteria: Using seaweed fertilizer provides excellent defense against microbes such as bacteria, parasites, and fungi. All of these are detrimental to the growth of any plant including cannabis, so you want to keep them away as much as possible while stimulating the growth of healthy bacteria within the soil.
growing marijuana
Photo by Cappi Thompson/Getty Images

How to Use Seaweed as Cannabis Fertilizer

There are many different kinds of seaweed fertilizers already available in the market:

  1. Liquid: Liquid seaweed extracts will likely need to be diluted, but to be sure, check the manufacturer’s guidelines. The dilution ratio will vary from one product to another though it is always best to check because you don’t want to risk overfeeding marijuana plants. Underfeeding is less risky than overfeeding.
  2. Powder: Feeding your plants with a seaweed foliar spray offers numerous benefits. Just add around ½ teaspoon of powder for every 5 liters of water. You only need a small amount to feed the cannabis leaves.
  3. Meal: Kelp meal is best added directly to the soil four months before you plant the seedlings. Doing so in advance will give the soil enough time to break the nutrients down, so that it’s efficiently absorbed by the soil. The typical volume for kelp meal is around 0.5kg / 9 cubic meters.

Below are ways you can use the fertilizer to improve the growth of cannabis plants:

  • Use seaweed to feed the roots of cannabis plants in all stages of its life cycle;
  • Soak seeds and cuttings in a seaweed solution;
  • Add kelp meal into the root zone;
  • Spray the foliage with seaweed extract – though this is particularly helpful when the plants begin to bloom. This should also be done during the start of the lights-on cycle;
  • Adding liquid extract or whole seaweed into compost together with other bio feeds;


Seaweed and kelp are wonderful organic fertilizers for all plants including marijuana. Seasoned cannabis growers know that seaweed is perhaps the best way to increase crop growth and boost the health of marijuana plants. Why not give it a try today?

This article originally appeared on and has been reposted with permission.


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