Botany Made Easy


The Least Understood Plant Nutrient and the Most Neglected!

Potassium is the least understood of all plant nutrients, plus it is expensive to put into fertilizer. So it has been the most neglected nutrient in plant fertilizers. Other plant nutrients end up forming part of the actual molecules and cells that make up plants, but potassium is not found in any molecules anywhere in plant tissues! So why is it important? We never really knew before. Only experience over time taught farmers that plants go downhill, stop producing, and eventually die without potassium. Finally now plant science is advancing, and little by little we are learning more about this unusual nutrient.

Potassium for Hibiscus
Potassium makes plants healthier in every way ~ lush green growth, more blooming, bigger flowers with more colors.

All Plants Need Potassium, Not Just Hibiscus

For years we have been telling hibiscus gardeners about the extreme importance of high levels of potassium for hibiscus, but it turns out that potassium is just as important for other plants too! It is the most neglected of all plant nutrients for growers and gardeners of all kinds of plants. Scientists and growers are discovering that many (possibly most!) plants need to have more even more potassium than nitrogen in their fertilizers.

So what does potassium do? Why is it so important? There's still a lot we don't know, but one thing we do know is that plants suck up huge quantities of potassium if it is available in the soil. The more a plant grows, the more potassium it needs. The more the roots grow, the more potassium it needs. The more it flowers and fruits, the more potassium it needs. This applies not just to hibiscus, but to most, or perhaps, all plants. Potassium must be extremely important in all aspects of plant growth because of the huge need plants seem to have for it. So with the help of recent scientific research, let's see if we can pin down a little bit more about what exactly potassium does.

Potassium is the Key to Building Cell Sap

Potassium is found in the cell sap of plants. This is the nutrient-filled water that hangs out in the empty spaces inside cells. Cell sap can take up to 80-90% of the space inside cells. Potassium is key to the creation and maintenance of cell sap. Plenty of potassium keeps the cell sap spaces, or vacuoles, plump, full of cell sap, and able to hold all the nutrients that do so much to make plants healthy. We don't yet know all the important things that cell sap and potassium do, but here is what we do know:

Cell sap makes strong wood, stalks and branches:
When all plant cells are full of cell sap, the plant stands up straighter, taller, with heavier, fuller stalks and branches. The pressure of the cells against the outside of the plant helps build stronger wood. When a plant is deficient in potassium, it will start to look more stunted with weaker, floppier wood and branches. Eventually cell sap will diminish to the point where the plant starts to look limp, and in severe cases of deficiency, the plant can slowly collapse and die.

Potassium for Hibiscus
Potassium makes all plants healthier, not just hibiscus. The California pepper tree in the left foreground received only potassium twice per month. The California pepper tree in the right background received no fertilizing. After 2 years, the left tree built taller, stronger, more upright wood, many more berries, and darker & glossier green leaves. The tree without potassium at right had weaker, sprawling branches, less growth, fewer berries, and lighter & duller green leaves. Potassium alone built a much stronger, healthier tree, even without any other fertilizer.

Protein and amino acids are stored in cell sap:
Cell sap stores proteins and amino acids that plants use to build everything - wood, leaves, flowers and pigments. More and healthier cell sap is able to hold more of these building blocks for more and better plant parts. Plenty of potassium makes plenty of cell sap, which in turn makes a healthier plant with lots of lush green leaves and large, fully developed flowers.

Flower pigments are stored in cell sap:
Cell sap contains flower pigments that make all the different colors in flowering plants. The more potassium and cell sap a plant has, the more pigments it is able to store and use to make flowers with the widest variety of colors and the most color-saturated pigments. The anthocyanins that make blues, browns, and the deep reds are water soluble and fragile, so these are the colors that completely depend on cell sap, and hence potassium. With insufficient potassium, flowers don't develop these colors. With high amounts of potassium and super healthy cell sap, the blues, browns, and deepest reds become much darker and brighter.

Glucose is stored in cell sap:
The main food that plants use for the energy of growing and blooming is glucose. Glucose is stored in cell sap, and like all other nutrients in cell sap, the healthier and plumper the cell, the more glucose it can hold, and the more fuel there is for the plant to grow and bloom.

Cell sap helps drive away predators:
Healthy plants break down old, dying cells in cell sap. This process releases a bitter taste throughout the plant that bugs and animals don't like, so it makes them stop eating the plant. It's a sad fact that a plant that has been stressed by heat, drought, flooding, cold, or any other environmental stressor almost always ends up getting a bug attack right at that moment. This is because a sick plant can't break down its dying cells to create the protective bitter taste. A stressed plant needs extra potassium to help turn dying cells into the bitter taste that will deter predators.

Cell sap recycles plant parts:
When plant waste is broken down, the cell sap stores the different molecules so the plant can use them for new parts. So healthy cell sap functions as a sort of recycling center for plants, making sure that waste does not build up but gets reused to make new healthy plant parts instead.

Cell sap stores toxic substances that fight off predators:
Toxic substances that enter a plant are moved into the cell sap and stored there. This prevents damage to the plant primarily, but it has the secondary function of making the plant toxic to different types of predators.

Potassium is the Switch that Turns on Many Plant Processes

Potassium is a little chemical switch, called a co-factor, that switches on processes all over the plant, from photosynthesis to building of proteins, creating sugars, transporting nutrients, storing energy, storing sugars, and many more. It is a co-factor in more than 60 different processes in plants ~ way too many to list here. Scientists will surely soon discover many more that we don't yet know about! In order for plants to grow, get nutrition, use energy for flowering, and everything else plants need to do, they have to have plenty of potassium at hand, all over the plant, to switch on every one of these processes.

Potassium is the Transport Supervisor for the Whole Plant

Potassium is involved in every aspect of transport in a plant, moving food, nutrients, and chemicals all through every part of the plant. Plants don't have little pumps in them to move nutrients around - they don't have a heart that pumps like animals do. So they move nutrients by a passive process called osmosis, aided by potassium. Potassium floats as free ions in the water all through the plant, and pulls water and nutrients in its direction. Where there is more potassium, more water and nutrients are pulled - into cells, up into the plant from the roots, wherever water and nutrients are needed. Potassium is necessary to keep every single part of the plant properly fed and hydrated, from roots, stems, and stalks to leaves, flower petals, and each individual cell that makes up a plant.

Potassium Controls a Plant's Breathing or "Transpiration"

Plants "breathe" or transpire through tiny holes all over all the leaves called stoma. When a plant is plump and full of water, the stoma are wide open, pulling in maximum amounts of carbon dioxide to use to make food. When water levels are too low, potassium makes the stoma close up to seal off any loss of water and prevent the plant from dying of thirst. When water levels are high again, potassium opens the stoma back up so the plant can start to make food again. It is because of potassium that our plants go limp when we forget to water them, then pop back up again when we remember to water them. This does stress our plants, but thanks to potassium, they don't die!

Potassium Provides Some Frost Protection

Potassium helps protect a plant from frost in several ways. First, it helps plants make more sugars, and sugar is a natural anti-freeze. When the cell sap has plenty of potassium, the plants can store more sugars, packing more of this sweet anti-freeze into each cell of the plant. In addition to this, potassium itself functions as an anti-freeze! So a cell that has a lot of sugar and potassium both will have the strongest possible anti-freeze protection and can survive light frosts easily.

Potassium for Hibiscus
Potassium, potassium, potassium! For gorgeous hibiscus plants, use plenty of it!

Just Remember ~ Potassium, Potassium, Potassium!

This article is a very short introduction to a very complex subject. It would take many more pages to detail everything we are learning about potassium in plants, and scientists have only just begun understanding this important nutrient. More information will surely be pouring in over the coming years. But whether or not we fully understand how potassium works, we really just need to understand that it is one of the very most important nutrients that all plants need in order to be strong and healthy.

So what does this mean in practical terms? We pack as much potassium as we can into our Special-Blend Fertilizer. If you use it, you are already ahead of the game! For absolutely optimal health and blooming of your hibiscus, we do recommend adding extra potassium to hibiscus with our Hibiscus Booster in order to give your plants even more potassium than can be put into our fertilizer.

If your plants stay in pots and you use our Houseplant Formula, you don't need to add Booster, since we are able to pack very high amounts of potassium into that type of liquid fertilizer.

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