If you’re growing cannabis in soil, you have about as many options to try as there are strains of marijuana to grow. Growing in soil is great if you like the idea of a somewhat forgiving substrate or don’t want to have to learn all the details of hydroponics growing.
There are a lot of different ways to grow in soil and a lot of debate in the industry about what makes the best soil for growing marijuana plants. One of the most misunderstood and overlooked additives to a marijuana soil mix is worm castings for cannabis crops.
What does it bring to the table and is it a part of the best growing soils?
Figuring Out the Top Dirt for Growing Cannabis
When you’re trying to grow cannabis, a lot of different factors play into the decision of what material to add to your soil. Are you growing indoors? Out in a field? In a pot or container on the back porch? What about moisture in the air? Is the plant going to be in direct sunlight all the time? What type are you trying to grow? Is it autoflowering or photoperiod? Confused yet?
Making Super Loam
If all these questions are making you feel like you need a hit, you’re not alone. It almost feels like you need a PhD in soil science to be able to grow a damn weed plant these days. Luckily, there’s a simpler way to achieve substantial crop yields without a lot of hassle and effort.
Hands-Off PH Management
One of the battles that most cannabis growers deal with is maintaining the pH level of the soil (or liquid in hydroponics) throughout the grow. One of the amazing things about adding the right amount of worm castings to the soil is that it will help you manage the PH level at an optimum range for marijuana growth. The generally accepted range that many growers try to stay within is anywhere from 6.0 to 7.0. Cannabis seedlings grow best when the PH level is just slightly acidic, meaning the number is just below 7.
The pH level of pure earthworm castings is roughly 7.0, or neutral. When you add a rich black peat dirt or compost that has a more acidic PH, the worm castings help get the whole mixture into that optimal range of 6.0-7.0.
Wouldn’t it be nice to be able to not have to mess with the pH balance of your soil every day? Adding chemicals, minerals, fertilizer, and other nutrients to get the pH into that perfect range?
With the right amount of worm castings mixed in, you won’t have to do much. Mix at least 20% castings into a good soil or compost mixture at the start before you plant the seed, test the pH and then leave it alone. Depending on what exact mixture you’re using, you might only have to add more castings once a month or once every couple of months. They will help regulate the pH and keep it at that perfect growing range throughout the grow.
What’s the Right Percentage When Mixing Dirt for Marijuana?
So how much worm castings should you use when making soil for marijuana? There isn’t really a 100% correct answer for every situation. You could grow in 100% worm castings if you want.
There isn’t a ton of scientific research out there to show what the exact percentage should be. One study found that a mixture of up to 80% earthworm castings and 20% dirt was the most effective for growing cannabis.
We would recommend running some tests with the strain of marijuana that you’re using, with any other additives that you plan to include and see what works best for you. Anywhere from 20% worm castings up to 80% will have a positive impact on the development of the plant and root growth.
Mixing with Other Supplements
When making your perfect weed super soil, there are many different products or growing mediums that you could throw in. Some of the most popular choices are perlite, bat guano, and coco coir.
Perlite is often used to help the growing medium with drainage. This is beneficial because it doesn’t allow water to build up in the soil and create rot in the roots of the plant. Some experts recommend a mixture that contains up to 30% perlite. However, if you’re adding in a higher concentration of worm castings to the mixture, you can reduce the percentage of perlite you use. Worm castings are great for aeration and water regulation in the soil. Therefore, you get some of those benefits from the worm castings.
Coco coir is a popular base for growing marijuana in because of its ability to provide aeration and drainage. It is lightweight, cheap, and easy to use. The percentage that you use of coco coir can also vary, depending on your preference and needs. Many growers recommend using between 30 and 50% or more. Again, if you’re using a larger concentration of worm castings, you can scale back on the coco coir because of the benefits that the castings provide.
Make Living Earth
The big benefit of using worm castings when making soil for cannabis is that it improves the microbial life substantially. High-quality worm castings can provide microbes (such as helpful bacteria and fungi) like nothing else. If you’re trying to grow marijuana in an organic manner, you really can’t beat it.
The microorganisms help break everything in the soil down to an easy-to-digest format for the plants. They soak up all the good matter and get a constant stream of nutrition throughout the grow. Don't be so caught up with the NPK ratings (which talks about the rate of phosphorus, nitrogen, and potassium in a supplement), the microbes more than make up for the difference.
Cost - Throughout the weed growing community, there are some common misconceptions pertaining to worm castings use. One of the most common is that you should sparingly use worm castings because they are expensive. In reality, they’re not that expensive compared to a lot of the commercial super soil mixtures and other supplements or products.
You can actually increase the percentage of worm castings in the mixture without having a big impact on the overall cost of the grow. If you’re already using a commercial super soil mixture, you won’t really notice a difference in money by increasing the worm castings percentage. You will, however, notice a difference in how easy it is to grow cannabis and the yield of the plant.
All Worm Castings Work the Same – One of the biggest misconceptions in the growing community is that all worm castings are the same. Nothing could be further from the truth.
Pure earthworm castings (not vermicompost from red wiggler worms) have a much higher microbial count and nutritional density. Simple Grow worm castings are produced in a controlled environment with a controlled, premium diet for the worms. This creates the finest manure with consistent nutrition for the plants.
If you’re used to using cheap, generic worm castings from the big box store, you’ll be shocked at the results you get from Simple Grow castings. Not all castings are created equally.
If you’re growing in drought conditions or simply don’t want to use as much water, worm castings will help a lot with water retention! The texture of the castings absorbs water instead of letting it all flow through and drain out. By mixing in worm castings at a 20% or higher threshold, you’ll be able to get water to the roots of the plant when needed. If you forget to water once in a while, this will bail you out!
Regardless of whether you’re growing indoors or out, using a quality living soil for your grow can produce some of the highest quality buds. Adding a higher concentration of premium organic worm castings can make your life as a grower easier, while growing better plants at the same time.