How To Control Potassium Deficiency In Cannabis

How To Control Potassium Deficiency In Cannabis

Have you ever wondered why your plants don’t have that ooh wee flavor or the smell that will have the whole block stankin?

You don’t want the entire block to stank, but you get the clue. It’s Potassium! Many of your flavors and smells come from the big K; I’ll show you how to pack more punch than Mike Tyson!

How’s it growing? I’m Cartier Crops, your home-growing personal guide.

Many home growers overlook potassium when it comes to growing, especially in the final stages.

How Does Potassium Help Plant Growth?

Potassium is the problem if your buds aren’t complicated or very airy and lack the terpene profile of the genetic. Not only does potassium help with flavor towards the end of the growth, but potassium increases the strength and resistance of the root system and the plant’s tissue.

Potassium will also help protect the plant from harsh, cold weather like silica does—another thing to focus on is the weight, density, and volume potassium offers.

Cannabis Leaf Symptoms

So how can you tell if you need more potassium in your plants? Cannabis leaf symptoms are the most common way you’ll notice deficiencies.

The marijuana leaves have brown or yellow coloring in the tips and edges of the leaves. As time moves on, these will curl UP, appearing burnt – much like an iron deficiency.

Stretchy plants are another indication of potassium deficiency.

If one plant seems taller than the others, it’s not a good sign as this weakens the stems.

It can be genetics, so you must understand genetics and whether you added enough potassium to the mix.

After burnt ends, the next step you’ll see are spots that creep up the leaf, slowing down plant growth. Slow bud growth is when real problems occur.

Since potassium is mobile when you have an issue, it will move through the plant quickly, unlike nitrogen or phosphorus deficiencies.

What Causes Potassium Deficiency In Weed?

Before changing your grow medium or watering solution, look at your lights. With intense LED and HPS grow lights, you might be overheating the leaves where nutrient evaporation occurs.

Intense lighting will show burn symptoms even if the overall temperature is cool. Just make sure you check for this first. Move your plants further away from the lights for a couple of days to determine the issue’s root.

If lights are not the problem, an excess of fertilizers and nutrients might cause the deficiency. Excess salts will build up in the growing medium and create a lockout on your potassium uptake.

A nutrient lockout will cause most deficiencies. When the pH of the soil is too low, it makes the medium too acidic. Acidity causes stress in the root zone and will also prevent potassium uptake.

Nutrient Lockout Leads to Nutrient Deficiency?

You must ensure your pH is on point. On point means calibrating your EC/PPM meters before each crop and in the middle of crop production.

Suggested pH Levels:

  • Soil 6.0 – 6.7
  • Coco Coir 5.8 – 6.3 Max
  • Hydroponics 5.6 – 6

So, pH is one way to solve the issue, but you know how I rock. When in doubt, flush it out!

Another issue can be overwatering. When growing in soil, you want to keep a consistent watering schedule and use enough water not to let the salt build up in the medium.

If you experience salt build-up, you can use Florakleen or Sledgehammer to remove built-up salts throughout the growth cycle.

In coco coir, underwatering is usually the problem. Keep this in mind, coco coir is a soilless media and acts like hydroponics; watering each day is ok if you use the correct blends like Coco Loco, Mother Earth +Perlite, or Canna Coco

Here’s A Helpful Tip:

Good run-off should be 30% of what went into the growing media.


Make sure you read the labels of your supplements to see how these nutrients interact with each other. Too much of some will lock out others.

Calcium and nitrogen will decrease the absorption of potassium, for example. Just be sure not to use too much of something without fully understanding what it does.

If you run into issues and get confused, flush your plants with plain/0ppm pH’d to water. Test the water’s runoff to understand what’s missing or excessive.

Let’s say you test the water, and it reads higher than you want at the current growth stage. Then, you can continue flush until you get the desired number.

But suppose the number reads lower than expected. In that case, you can use a base nutrient mix to increase levels within the media, watering with a blend (base) of nitrogen, phosphorus, and potassium.

Other than my base nutrients, I like to give added potassium towards the end of my cycle, around week 7ish depending on the genetics I’m running.

Products like Sugaree, Terpinator, or even Cha-Ching can give you a considerable advantage when used correctly.

TIP: Do not use the products I mentioned together in your final weeks. Please choose from these or the list of items I suggest in this blog post. Once you get good at spotting cannabis deficiencies, you will understand what to use and how to use a specific element.

Here are keys to remember if you feel potassium deficiency is the problem:

  • When in doubt, flush it out
  • Calibrate the pH meter regularly
  • Use an additive final week of flower

I’m Cartier Crops guiding you to bigger, better-tasting crops without losing your mind and investment. Our private community helps you grow weed easy where you are the hero of your garden.