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Best Worm Castings for Cannabis

Last Updated: October 10, 2023
Roy Stevens
Product Review by Roy Stevens

Let’s be honest, every grow room is different, so to the equipment and brands each cultivator favors. This can also be true of the nutrients, cannabis mediums, and amendments.

It takes time, and lots of experience over many seasons to find out what’s best for your situation and grow. Even then, picking the best worm castings amongst the many top-rated brands out there can be a bit hit and miss.

Most growers tread with care when including any new amendments into their grow schedule, I also count myself as one of them.

However, there comes a time when you’ll inevitably need to introduce new nutrients, soil mixes, and the like into the situation, even if your set-up is near perfect, it could be for many different reasons, but will undoubtedly happen at some stage.

But, it doesn’t always have to be synthetic, there’s plenty of organic options out there that produce some very impressive results.

We’ve included 3 of the best worm castings for cannabis below, so carry on reading to find out who made the cut, and which one could transform your ok harvest into a sublime one.

Our Reviews

Mountain Valley Seed Company Organic Worm Castings

Mountain Valley Seed Company Organic Worm Castings Fertilizer is a microbial-rich waste by-product of the red earthworm.

This OMRI certified organic fertilizer is produced using cow manure that has been digested, processed, then refined by red earthworms and wigglers to create a fantastic all-natural organic by-product that will help your plants thrive.

Fortified with essential bacteria, microbes, and slow-release NPK, whilst always a neutral 7.0 pH, the Mountain Valley Seed Company Organic Worm Castings Fertilizer is great for indoor and outdoor gardens.

These earthworm castings will help minimize disease in your plants, whilst helping to maintain water retention which will then supply your indoor your plants with the beneficial nutrients they need.


  • Highly rated
  • OMRI certified
  • Odorless organic


  • None

Wiggle Worm Organic Worm Castings

These organic worm castings from Wiggle Worm are highly rated, well priced, and OMRI certificated. They can be used as a builder, conditioner, amendment, and compost for your cannabis plants.

Wiggle Worm Organic Worm Castings are both odor-free and naturally organic. Wiggle Worm prides itself on not adding any additives or perfume to the mix. Your delicate seeds and bedding plants are completely safe and should be protected from any burns.

Overall these worm castings should improve both aeration and soil structure. Whilst adding a significant amount of beneficial microbial, and bacterial activity

These Organic Worm Castings deliver fantastic results for indoor grows and can also be used for growing hydroponically.


  • Highly rated
  • Completely organic
  • Great price


  • Rubber Gloves Are Fairly Cheap

Brut Worm Farms Organic Worm Castings

Designed for the organic gardener Brut Worm Farms Organic Worm Castings are rich, dark, pure, and high in organic matter that delivers long-term nourishment.

With a host of healthy microbes and bacteria, Brut Worm Farms worm castings are balanced in all the minerals and nutrients organic worm castings need to help keep your plants healthy and happy!

Every bag contains the freshest of worm castings, usually within a week old, this helps guarantee you receive only the very best organic amendment for your plants.

The Brut Worm Farms Organic Worm Castings are perfectly suited for both indoor and outdoor grows, odor-free and Non-toxic.

Locally grown on a farm in Minnesota, rest assured no production is outsourced, so worry not if your castings will come with unwanted extras such as sand, sticks, and other unnatural items that don’t belong in worm castings.


  • Competitively priced
  • Produced in the USA
  • Highly rated


  • Pricey

Coast of Maine Organic Earthworm Castings

These highly rated MOFGA approved worm castings are produced by one of the most well-known and well-respected brands; Coast of Maine. Often used by cultivators to enrich the soil with the optimal active biology and plant-ready minerals by way of top dressing cannabis plants or blending with your chosen soil.

The Coast of Maine Organic Earthworm Castings is a superbly rich blend of digested by-products left by earthworms. Teeming with microbial life, this odorless, soil amendment helps to ensure your cannabis plants are getting the nutrients they need to thrive in a more plant-available form.

The earthworms used by Coast Of Maine are fed on a diet of peat, paper sources, grains, rock dust, and inoculums to promote biological diversity.

With the Coast of Maine Earthworm Castings, you will notice improved structure, root growth, alongside enriching the soil with a host of microorganisms.


  • Approved for organic growers
  • Well-known trusted brand
  • Quality worm castings


  • Pricey

Dr. Verm's Premium Organic Worm Castings

Another contender for your organic worm castings is Dr. Verm’s Premium Organic Worm Castings. Highly rated, but coming at a similarly high cost, these castings naturally improve conditions in your soil whilst being completely safe for your cannabis grow.

Dr. Verm’s Premium Organic Castings improves both germination, and root health, containing natural growth hormones that help to stimulate root development and germination.

The trace minerals and nutrients help feed your cannabis plants throughout their life-cycle, culminating in a healthy and bountiful harvest. With stronger resistance to both disease and pests, which is due to being high in enzymes.

Dr. Verm’s Premium Organic Worm Castings are teeming with beneficial microorganisms that improve your plants’ nutrient uptake.


  • 100% Chemical and Additive Free
  • Odor Free
  • Top Rated


  • Expensive for the amount

When you’re cannabis plants are in need of that little bit extra, it’s imperative you do your research thoroughly, and ultimately pick the best worm castings for your own situation.

Advice on grow forums is great and all, but they’re not hands-on like you are. They can only guess from the information you’ve provided them with. Of course, there are always grow guides and cannabis books, but again, only you can ultimately diagnose what’s right in front of you.

Learning how to grow as naturally and organically as possible is always best when you first start off, both for yourself, and your buds.


Without further ado, our choice out of the worm castings we’ve reviewed today is the Wiggle Worm Worm Organic Castings. Highly rated, competitively priced, and producing some great end results, Wiggle Worm would be a great addition to most cultivators cannabis grows.

Well, that’s it for today, hopefully, you’ve found the best worm castings for cannabis, or we’ve at least put you on the right track. Remember, you can also check out our many guides on how to set-up your grow room correctly, and with proper care, along with many more helpful guides.

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