Homegrown with Jim Berry: Feeding Cannabis Plants

June 20, 2026
By Jim Berry

This article was first shared in the Prisoners edition of Fat Nugs Magazine, published in February 2025.

Welcome back to Home Grown! I feel blessed to not have a relatable story for this issue. I have not, nor has anyone dear to me, been in any serious legal trouble over the use or cultivation of this miraculous plant.

The closest I’ve ever come was sweating it out with a sheriff’s deputy as we stood outside my home. Back in those days, law enforcement had a hard-on for caregivers. My neighbor had his caregiver’s grow raided by the sheriff’s department a couple of months prior. He was nowhere to be found, and they were asking me if I knew anything about his activities or whereabouts.

Of course, I said nothing helpful – because snitches get stitches. But we had this conversation right next to where I was venting heat from my grow room out the side of my house. To the unaware, it just looked like an oversized dryer vent. As for the smell, let’s just say, HUGE shoutout to Phresh inline carbon filters.

That conversation was it. He left, and I finished my panic attack, smoked a joint, and went about my day. I wasn’t arrested. I didn’t go to jail. I certainly didn’t go to prison, as many have and where many still sit today. It’s important to honor them and tell their stories. Many literally paved the way for my cozy little home that I get the opportunity to share with you.

Feeding Cannabis Plants: Salts v. Soils

In this issue, I am going to tackle one of the most heated, most controversial, most polarizing issues in cannabis… feeding cannabis plants with salts v. soils.

In order to grow a thriving, happy cannabis plant, a lot of boxes have to be checked – the right light, temperature, water, CO2, and, of course, nutrients. There are 17 elements that are essential for proper plant growth. The plant is able to uptake three of these (hydrogen, oxygen, and carbon) directly from the air and water. The rest are absorbed through the root system from the substrate.

That substrate could be made from any number of materials, but as home growers, soil, coco, and rockwool are mostly commonly available. Rockwool and coco are inert, having little to no nutritional value for the plant. They are just a place for nutrients, water, and oxygen to be available to the plant through the root system, or rhizosphere.

Soils have nutrients already available from the decomposed organic matter that makes up part of its structure. A well-manufactured soil will be nutritionally complete: plenty of water and air-holding capacity, and the proper pH for plant growth. Whether it has enough nutrition for the plant’s life cycle will depend on the demands of the plant and the overall volume of soil available to the plant.

All three of these substrates have the right pH. Coco will often have perlite added to improve air-holding capacity. But coco and rockwool rely on a steady supply of fertilizers to feed the plant. These fertilizers are typically dissolved in water before you irrigate the plants.

Unlike soil, the amount of substrate is less relevant, as long as the plant has a steady supply of fertilizers and water. In fact, it is often easier to manage the amount of fertilizer available to the plant in a smaller container. But the smaller the container, the more often it will dry out, and the more often you will have to water. If you choose to grow in an inert substrate, you may eventually look into an automated irrigation system that you can set to water multiple times a day while you’re living your life.

What’s Up With the Pot?

Finding the Right Size for Homegrown Cannabis Pants

How big of a pot should you use? It depends on the substrate. I often suggest to new growers that if they choose coco, start with a one or two-gallon pot. Rockwool comes in blocks, and a 6” cube is common, equal to about a gallon of substrate.

With soil, I like to say, “Go big, or go home.” But you’re already there. So start with at least a cubic foot, or about 7 gallons. Even with a large pot, don’t be surprised if you eventually have to feed the plant additional fertilizers. If I plan on irrigating with just plain water, I may plant into a pot that is 15 gallons or even larger. After a few cycles, you’ll find your sweet spot.

As a new grower, I started in soils, as they can be more forgiving. As a more experienced grower, I came back to soil. I’ve not only learned to maximize my yields, but I also enjoy the overall bouquet and effects of a soil-grown product.

Herein lies the controversy: does soil actually produce a more robust flower? Many would argue no. I disagree. But as your experience grows, you’ll get to decide for yourself. Each of us will develop our own style over time. There is no one perfect way to grow. You’re only competing with yourself and how well you did on your last round.

If you decide to start in soil, it can be simple: use (at minimum) 15 gallons of good-quality soil and irrigate with plain water. If you live in a municipality that treats the water with chlorine or chloramine, it’s a good idea to dechlorinate the water before you use it. If your water has chlorine, you can just fill a container and let it sit for 24 hours with no lid. The chlorine will slowly evaporate. Add a simple air bubbler to the container, and the chlorine will evaporate much faster. If your water has chloramine instead, you’ll need to treat it with an agent to remove the chloramine, something readily available at an aquarium supplier or online.

You don’t need to dechlorinate your water, but chlorine will kill bacteria and fungi that are living in the soil. Many of those microbes are beneficial to the plant, so removing the chlorine first will ultimately contribute to the overall health of the plant.

Feeding Cannabis Plants: Overwatering, pH, and Electrical Conductivity

Overwatering

Probably the biggest mistake I see new soil growers make, besides choosing too small of a pot, is overwatering. Soils are capable of holding much more water than coco or rockwool, and roots need to breathe. An oversaturated pot is also a breeding ground for bacteria that are not beneficial to the plant. Try to keep the plant consistently moist. If you see excessive water running out of the bottom after a minute, fungus gnats flying around, or your pots are sitting in standing water, you’re watering too much.

Coco and rockwool hold less water. You almost can’t overwater them. But since the plant relies on a steady supply of fertilizers, it is much easier to over- or underfeed them. For this reason, I recommend that you pick up a couple of tools that will make your life a lot easier: a pH (part hydrogen) meter and an EC (electrical conductivity) meter. You could pick up a set for as little as $20 on Amazon or spend $250 on a reliable combination meter from Bluelab.

Electrical Conductivity

The EC meter measures the amount of electrical resistance in your solution, which gives you an accurate idea of how concentrated the solution is. To keep it simple, aim for an EC of about 2.5. Adjust this number lower while they are vegging, or increase it if you notice a hungry plant in flower.

Mix your fertilizers according to the manufacturer’s recommendations, then measure the EC. If the EC is too low, add a bit more fertilizer. If the EC is too high, dilute the solution with plain water until the numbers hit.

The Right pH for Feeding Cannabis Plants

Each element is absorbed best by the plant at a specific pH, different for each one. A pH meter will allow you to make sure that the pH of your solution is set to a “happy medium” where all elements can be absorbed efficiently enough. A good rule is to keep the pH of your solution between 5.8 and 6.0. Check out the nutrient uptake chart for reference.

After mixing your nutrient solution, check the pH. Liquid products for adjusting the pH up or down are available at a hydroponic store or online. I recommend mixing in tiny amounts and rechecking the pH a few times. These products are usually fairly concentrated and it’s easy to overuse them, causing dramatic shifts in pH.

Whether you are lightly feeding soils, or consistently feeding rockwool or coco, there will be a propensity for unused fertilizer to build up inside of the container. That build-up will eventually cause the EC inside of the pot to spike. In simple terms, the water essentially becomes too thick with fertilizer and the plant isn’t able to drink efficiently. The plant won’t be able to properly cool itself and certain nutrients could reach toxic levels.

The build-up of nutrients will also affect the pH, likely lowering it. If the pH gets too low (or too high), the plant will no longer be able to uptake certain nutrients at all, which will cause a cascade of issues. Again, see the chart.

Measuring Your Feeding Runoff

With coco and rockwool, it’s a good idea to slowly overwater them regularly. Not every time, but just a bit, enough to produce a little runoff. It’s the fluid that has slowly seeped through a saturated substrate and eventually out of the bottom. And each time, it will carry with it some of those extra fertilizers, helping prevent them from building up in the substrate.

Measure the EC and pH of that runoff. Comparing those readings to the readings of your fertilizer solution gives you an idea if you are overfertilizing. If the numbers are drifting significantly, you’ll need to produce more runoff or cut back on the concentration of your fertilizer.

If you’re growing in soil, producing runoff is unnecessary and counterproductive. You’re already overwatering and you’re flushing valuable nutrients and microbial life right out the bottom. If you’re fertilizing soils, you may want to produce a little bit of runoff from time to time to check the EC and pH. Don’t be surprised if the EC of that runoff is very high, especially early in the grow cycle. I’ve seen EC readings from soil runoff that were over 6.0 and yet happy, healthy plants without a care in the world. Expect to see higher pH readings, even a little over 7.0. It’s completely natural for cannabis in soil and an excellent indicator that the pot is very much alive with beneficial bacteria, as they are largely inhibited and even killed by more acidic conditions.

This is just a primer on fertilizing options and techniques. But hopefully, it’s enough to set you on your journey or give you a lightbulb or two. Never give up on the journey. Never be done learning.