Potassium Deficiency during Flowering Stage

Potassium deficiency is one of the most common marijuana deficiencies, generally its symptoms appear when the plant enters its flowering stage.

If you see that the tips of the old leaves begin to take on a strong yellow hue between the veins. Or if you see the tips and edges start to get ‘burned’. Chances are you’re facing a potassium deficiency.

This deficiency can cause your plant a lot of problems. Among which stands out the little growth, low production of buds, or skinny buds that fail to gain weight despite maturing.

Potassium is essential for your plant to develop flowers as well as in the growth stage. From the beginning it is necessary for it to grow strong, develop the stem well and improve its resistance to cold and disease. It also helps in essential functions such as temperature regulation, respiration, and even photosynthesis.

You should not worry if the problem is not spreading and what you see is only two or three sheets showing this lack. If you see the problem progressing to more sheets then look at some of the solutions listed below.

Colors and Symptoms of Potassium deficiency

In Lower & Medium Leaves

chart-potassium-deficiency-marijuanaThe ways in which a potassium deficiency manifests are several and not necessarily similar to each other. It is often confused with overfertilization or other totally different deficiencies.

At first the plant will appear to be in very good health, growing even taller than the others. However, soon after, different spots appear on the leaves.

That the leaves turn yellow starting at the tips and gradually advancing towards the base of it is one of the most commonly visible symptoms.

The ‘burn’ of the edges and tips of the leaves is another of the usual symptoms. Since potassium is essential in the regulation of temperature, lacking this, the leaves do not regulate correctly and come to ‘burn’. These burns can resemble overfertilization.

The distinction with the symptoms of overferlization is that in the latter, the potassium burn will be limited to the tips. In the lack of potassium it will also come out on the edges and in a short time it will be accompanied by yellowing, although it is minimal.

Depending on your case, you may see yellowing or “burns” first. If this advances the sheet will continue to lose color and burn, spots of dead tissue will appear, until it wrinkles and ends up dying.

If you find red, brown, or gray spots on the stem, this may also be the cause.

In Upper Leaves and Shoots

Sometimes you will see these symptoms on upper leaves. Potassium moves freely around the plant and it will eventually show up in upper leaves.

If the deficiency begins to be severe you will notice that your plant has slowed its growth. The new shoots will not grow as fast and their leaves will be small compared to the old ones.

In the Buds

Potassium deficiency delays flower formation, decreasing flower volume and harvest grams. Potassium plays a key role in bud formation by increasing its weight, density and volume.

If you lack potassium in your flowering stage, you will only have skinny and poorly developed flowers. The other essential nutrient for the flowering stage is Phosphorus, commercial fertilizers for flora are mainly loaded with potassium (K) and phosphorus (P).

Potassium Deficiency Pictures

How to solve a Potassium Deficiency?

If are already fertilizing the substrate, you should not have any of these symptoms. So before solving the problem you have to find out the reason for the lack of potassium, almost at the end I listed other causes that can lead to a potassium deficiency even if there are enough nutrients.

In case you’re not giving enough fertilizer, check out the sections below.

Flowering Fertilizer

Flowering Fertilizer

As usual, the easiest and safest way is to buy flowering fertilizer in a grow or nursery. Marijuana is a plant like any other and the flowering nutrients are the same. But before choosing a fertilizer let’s see some things.

The nutrients that we will look for in a flowering fertilizer are potassium and phosphorus. In these the amount of nitrogen, phosphorus, potassium (N-P-K) they contain is specified, the nitrogen being less necessary in flowering.

There are two types of fertilizers, organic and mineral or chemical. The organic one will be of slower absorption and very beneficial for the soil, the chemical or mineral is more precise and will go directly to the roots.

If you buy a chemical from a non-specialized nursery, make sure it is suitable for edible plants.

Banana Peel Tea

The homemade fertilizer that is most discussed in the cultivation groups. It is not only used to solve deficiencies but also to fatten buds during flowering.

You’ll find plenty of Potassium and Phosphorus, the key nutrients in flowering, in the peel — and the banana itself if it is ripe.

True banana tea is actually a cold tea, despite the fact that it is commonly used to boil. If you leave it to soak an organic ‘waste’ in water for enough days, it will begin to pass its nutrients into the water thanks to the formation of bacteria.1 Otherwise, if you boil it, you will not get as many nutrients and many will be lost due to high temperatures.

How to dot it the right way:

  • Let the water sit for at least 24 hours to clean it.
  • Cut the banana peels into pieces.
  • Put the pieces in a jar filling about 5 centimeters.
  • Finish filling up to 3/4 of the total content with water.
  • Cover it with a rag.
  • Let it rest in the fridge for 3-5 days.
  • Stir it a couple of times a day.

Note: if you see that there are gases in the jar it is normal. On the other hand, if you see any type of mold accentuating, we must start again.
The tea should smell sweet and banana like. If it has an acid or rancid odor, do not use it, try again, leaving it less days.

After a few days, all that’s left is to strain it — so as not to leave food scraps on the soil.

To water first you must dilute the tea in standing water, 1 liter of water for every half glass of tea — or 1 part of tea for every 10 parts of water. And water enough to water your plants normally.

This will provide your plant with significant amounts of potassium and phosphorous, as well as beneficial microorganisms for the substrate.

Don’t apply it too often, depending on the size of your plant, applying it to the irrigation water every 1 week will be enough. It is important never to overdo with fertilizers, better to apply a little many times, than a lot and to overdo.

Wood Ash

Sprinkled wood ashes

Wood ash is a touchy subject. I recommend it only if you grow outdoors directly on the ground. For pots it is preferable to use another method.

Starting to sprinkle ash on the soil during the first weeks of flowering will provide your plants with excellent levels of potassium.

But you must be careful, the ash when wet will generate lime and salts that in large quantities can burn the roots at most, or modify your pH levels generating deficiencies.

Start the plant slowly, using little ash and seeing how it reacts, to then increase the dose.

  • If you have a stove or grill, collect the finest ash you can find in a plastic bag, leaving aside the pieces of coal.
  • Take a handful and sprinkle around the plants above the ground, without touching leaves or flowers.
  • Take care not to cover all the soil. Take a look at the example photo.
  • Water normally with standing water from now on.

This will give you a good shot of potassium, and it will stay in the soil giving you nutrients for a while.

Be very careful not to sprinkle too much. And if you are applying this type of fertilizers, it would be better to start regulating the pH.

Bone meal

You can take advantage to add bone meal if you feel comfortable with fertilizing and maintaining the pH of the substrate. You buy it in any nursery and apply it the same way you apply ash.

It is a slowly absorbing fertilizer so you will have your plant ready to continue absorbing after recovering.

With bone meal you will have a great contribution of phosphorous, more potassium, calcium and magnesium. The ideal is to use it when we assemble the substrate so that it is present throughout the process.

Other Causes

Stress — from transplants, poorly done pruning, too much heat — can also cause it, if this were the case you should manage on your own after a few days.

Variation in the pH of the irrigation water or your substrate. If the pH of the substrate is outside the 6.0—7.0 range, the roots will not be able to absorb potassium, however much is available in the soil.

If the pH is correct, an accumulation of salts in the roots will also impair the absorption of potassium. For this, you can perform a root wash with the cleanest water possible. For his part, the author Alberto Huergo recommends adding two drops of organic detergent in the irrigation water.

“In addition to containing N.P.K, the detergent is good for its wetting properties and above all, it is very effective when there is excess salt …” 1

A light burn can form spots similar to potassium deficiency. Hard to hit the sun, but if you have an indoor, is it possible that the light is too close? Do you know what power your light has? Your plants can withstand a good amount of light but they have limits.

Important References:

  1. Alberto Huergo, “Sativa Cultivo Interior”—page 212—THC 9, 2008

Thank you for reading

Any of these recipes will solve the deficiency. In case after applying your plant continues to worsen, you can be sure that the cause is another.

You already know all the basic things you can know about potassium deficiency. I’m making a list of recipes for fattening buds in bloom taking advantage of the information I gathered for this post. If you want me to notify you when it is published, write down the list below.

What did you think of the publication? I wanted it to be wide and have options for everyone but without being annoying to read, for example I did not mention the bat guano despite being excellent.

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Santiago @ Dr. Cannabis
Santiago @ Dr. Cannabis
I'm here to help out marijuana growers have a greater experience with their plants, and not loose their mind over the many problems and situations that often arise during the different stages of cannabis growth.

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