too much potassium cannabis

Deficiencies Due to Excess Nutrients

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Deficiencies due to excess nutrients is a lot more common than you would think; many people believe that by giving their cannabis plants more fertilizers they’ll solve anything, and if your plants are showing potassium deficiencies then the best thing is to give them potassium. This isn’t necessarily true, as you could have easily over-fertilized your plants with nitrogen which annuls the absorption of potassium.

Deficiencies don’t always mean that your plant is lacking that specific nutrient in the soil – it might be that since last measuring the pH, more and more nutrient has accumulated in the soil and this could provoke blockage, as well as having too much of one nutrient can easily block the absorption of another.

In this article we’re going to go through a list of nutrients that are generally used in growing and can cause deficiencies when used in excess.

This is a nutrient that tends to be given to cannabis plants during their growth phase. Nitrogen is the mineral that your plant uses the most, but excess nitrogen can provoke various deficiencies in the future such as potassium and calcium deficiencies. An excess of growth fertilizer will cause your plants to begin flowering later, and you’ll see signs of potassium deficiencies or yellowing leaves due to an obvious calcium deficiency – so take care to not use too much growth fertilizer if you want your plants to flower healthily!

Potassium is generally found in flowering fertilizers or additives used during the bud fattening phase. An excess of this nutrient can cause nitrogen, calcium or magnesium deficiencies. It doesn’t matter how many micro-nutrients you use to try and solve the issue, if your plants have too much potassium they won’t be able to absorb what you need to give them – one of the best things you can do in this case is to wash the roots out completely to remove any excess, then give your plants the nutrients they need to get better.

Phosphorus is the nutrient your plant needs most once it begins the bud fattening stage. To grow large buds, plants need big doses of this mineral, but if you use it too soon it can cause excess and accumulate in the roots. If this happens, your plants won’t be able to absorb zinc, iron and copper. If this happens you’ll need to flush the roots before giving it anything else and make sure that it’s still not too early to use fattening products.

Calcium is essential for your plants, although they don’t need too much of it, and most of it is given in flowering fertilizers and from tap water. When giving your plants extra calcium you’ll need to be careful, as too much of it can disrupt the absorption of nutrients such as boron, magnesium and even phosphorus – this could be fatal for your plants if it happens mid-fattening period. If you notice a deficiency of any of the previously mentioned nutrients during this period then you’ll need to make sure you didn’t use too much calcium before starting to add extra stuff, as you might make the situation even worse.

Many different fertilizers give your plants calcium, and during the flowering period it’s usually given so that your plants don’t show any sort of deficiencies; an excess of this nutrient can cause both potassium and calcium to not be absorbed. If you use magnesium during the flowering period you’ll need to use it with osmosis water and a nice and controlled EC level – do not use in soil unless you’re trying to fix an obvious deficiency.

This mineral is generally used in keeping mother plants healthy, as they need high levels of this nutrient in order to keep up with the stress of constant cloning. An excess of this mineral can stop your plants from absorbing manganese, and your plants will most likely stop growing and the leaves will be quite ruined. If you use iron in your irrigation water, make sure that you don’t use it more than once every two weeks.

Sodium can easily be found in tap water, and if you water your plants for a long time with this kind of water you might end up with certain deficiencies due to excess sodium. That white lime-like substance that accumulates in your flowerpots is sodium, and an excess of it can cause deficiencies of potassium, calcium and magnesium. Using tap water can cause a whole lot of deficiencies, so it’s best to use osmosis water for your cannabis plants if you don’t want any nasty surprises.

Many different fungicides and insecticides use sulfur in their ingredients as it changes the pH of your plants surface area and gets rid of all kinds of fungi and aphid. Using these kinds of products ensures that you have no fungi or infestation issues, but using it too much can cause deficiencies such as molybdenum, which will cause your plants to begin going yellow – if you plan on using this product, take care to not use too much; once every 20 days before flowering to prevent issues and once every 10 days to cure your plants should be enough.

Before trying to solve a deficiency with more products, make sure that you’re certain that you haven’t gone overboard with any of these minerals in your grow. If you have, simply wash out the roots before solving the deficiency – there are various products on the market that can help you out with flushing the roots, such as Canna Flush by Canna.

Author: Javier Chinesta
Translation: Ciara Murphy

Deficiencies Due to Excess Nutrients – Find out how to identify deficiencies in your plants caused by excess nutrients in the soil.

Deficiency and excess of Potassium in cannabis plants


There are many nutrients that influence in the development of marijuana plants; on this post, we are going to point out the most important functions of Potassium. We will tell you how to treat deficiencies and excesses of this element and the effect it has on the plant metabolism, especially in cannabis plants.

Potassium is an element found in the land in mineral form. This mineral is more or less present according to the type of terrain. Soils composed of clay are by far the richest ones in potassium, containing up to a 3%.

The potassium cycle

This element arrives at the oceans and seas through rain, aquifers, rivers, etc, where it returns by evaporation to the sky in the form of water vapour. This vapour condensates and returns to Mother Earth in form of rainfall. .

One of the ways that potassium has for its self-regeneration in the land is through animal droppings. Potassium returns to dry land to be processed again by micro-life. The remains not used by plants will be swept away by the rain and led through aquifers into the seas and oceans to return again to solid ground and close the potassium cycle.

In those regions with constant rainfalls, the substrate doesn’t properly retain this nutrient, so it isn’t found in the substrate in sufficient quantity for plants. Potassium is easily carried away by water, so we should add potassium in the form of sulphates to out nutrient solution in order to make it available for plants.

Functions of potassium in cannabis plants

Early stage of potassium deficiency

Potassium is one of the most important nutrients for marijuana plants, and although it doesn’t have much presence in the plant tissues it performs important catalyzer functions in many metabolic processes as those we list below:

  • It takes part in the photosynthesis process improving the synthesis carbohydrates.
  • It participates in the synthesis of proteins and amino acids, which come from nitrogen in the form of ammonium, so the interaction between these two nutrients is vital to perform different metabolic processes of plants.
  • It improves the resistance of plants during drought periods.
  • It increases the consistency and strength of the plant tissues.
  • Together with Phosphorus, it improves the strength and resistance of the root system.
  • The resistance against frost is also increased by acting in the sap of the plant.
  • It increases the weight, density and volume of the buds.

Intermediate stage of potassium deficiency

If there is a potassium deficiency, plants will have visible symptoms that will help us to detect it. Potassium is a mobile element so it moves from older to younger leaves when needed, since the top part of the plant has always more metabolic activity. We should make sure that our plants have enough Potassium during their life, since any lack of this nutrient will be translated into lower yields.

In the case of having potassium deficiencies, you should add more fertiliser (rich in this element) either from organic or mineral origin. Organic fertilisers are more slowly processed than mineral nutrients, which will correct this deficiency in no time and will allow you to harvest decent buds. If the deficiency is at an early stage you can simply increase the dose of your organic or mineral nutrient, what will probably solve the problem.

Advanced stage of Potassium deficiency

Potassium deficiency in cannabis plants

Visible symptoms in cannabis plants:

  • The leaves turn yellow from the tips towards the centre, ending at the base of the leaf.
  • Plants are weak and have little resistance to diseases.
  • Stems are also weak and bend easily.
  • The final yield of buds is seriously reduced.
  • An excess of calcium can lessen the capacity of the plant to absorb potassium, leading it to a deficiency of this element.

Potassium excess

Symptoms of potassium excess:

  • Blocks the absorption of other elements such as calcium, magnesium, zinc and iron.
  • Given this situation, you should flush the roots with at least triple the amount of water than the capacity of the pot; you can also add any component that helps to flush the salts away and leach the substrate. Then, you should water with a light, complete and balanced nutrient solution.

Foto 1: Potassium deficiency

The plant in the picture #1 presented a potassium deficiency that has been treated on time, without losing much bud yield and quality.

This marijuana plant was grown in an inert medium – coco-coir – and suffered a deficiency during the flowering stage, when potassium is more needed, during the 6th and 7th weeks (This plant had a flowering period of 8-9 weeks)

In the picture #2 we can see how the plant has suffered a more serious potassium deficiency.

At medium height of the plant we can see how the tips of the larger leaves are burned. Moreover, you can see with ease a discoloration of the leaves to a more yellow colour.

Photo 2: Potassium deficiency

At the top of the plant we can easily detect that the plant has been negatively affected by this deficiency. The buds couldn’t develop completely and have remained in a quite decayed condition. .

The buds of this plant won’t have superior smell or flavor since potassium is essential in terpene production.

At this stage, if you didn’t provide the necessary nutrients the yield will be seriously decreased. The buds won’t be compact and the resin production will be minimal.

These deficiencies are usually more evident and frequent in Indica strains, which are often grown without much knowledge since their flowering stage is much faster than Sativas, and the maximum demand for potassium is centralized in no more than 1-2 weeks, depending on the strain.

Since Sativa plants take much longer to flower, their nutritional needs are more progressive than in the case of Indica genetics. Still, it should be noted that Sativa strains are more susceptible to be over-fertilised than Indicas, so you should pay close attention to their needs to have a crop free of deficiencies and excesses.

In this way, choosing a balanced hybrid strain will help to control any excess or deficiency of potassium and other minerals like nitrogen or phosphorus.

In this post we show you how to detect a deficiency or excess of potassium in cannabis plants, so you can have a crop without problems and harvest the