Feeding Your Plants

Feeding Your Plants.  Plant Nutrients.  Understanding Plant Nutrition.

Growing healthy plants isn't always easy, but it doesn't have to be complicated! I'll explain what you need to know to make sure that you are feeding your plants properly. Did you know that plants require nutrients just like we do?  I'll break down the basics of plant nutrition for you.

Happy, healthy plants are the most beautiful and productive!

🤚Before we dive in, I want to give you a FREE guide that will help you grow your best garden yet! Grab your free copy of the From Seed to Supper guide here and grow a bountiful garden this year!

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There are a few basic things that plants need to survive: sunlight, air, and water.  But is that it?

No! Plants require a range of nutrients to stay healthy just like people do.

Plants need ample amounts of sunlight, water, support from the soil (or other media), and nutrients.  There are 16 essential nutrients that plants need.  The exact amounts of each nutrient needed will vary based on the plant type, but these are pretty general across all plants.

​When you are getting the soil ready for your plants, you need to make sure that the soil has adequate amounts of nutrients in it to keep your plants healthy and flourishing.

The Sixteen Essential Plant Nutrients

The nutrients needed by the plants can be broken into what are called macronutrients and micronutrients.  Plants require some nutrients in large amounts.  These nutrients are called macronutrients.

Macro= large, so large amounts required.  The plant will also require nutrients in small amounts.  These nutrients are still essential to the plant.

Nutrients that are needed in small amounts are called micronutrients.  Some of the structures in the plant are reused.  Micronutrients are used in these structures.  When the structure is reused, the micronutrient is also reused.

What are the nutrients plants need to grow?

There are six macronutrients- nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Nitrogen, phosphorus, and potassium are referred to as primary macronutrients and are essential to plant health.

​When you purchase a bag of fertilizer, you will see three numbers on the bag that are separated by hyphens. The first number represents the percent nitrogen, the second number represents the percent phosphorus and the last number represents the percent potassium in that fertilizer.

fertilizing plants

So when you purchase a bag of 13-13-13, or triple 13, you are purchasing fertilizer that is 13% nitrogen, 13% phosphorus, and 13% potassium.  Some fertilizers are more specialized and have 0's.  These fertilizers are used to provide the plant with specific nutrients.  For example, 0-30-0 is a fertilizer that contains no nitrogen, 30% phosphorus, and no potassium.

The following nutrients are essential for plant growth and development.  If you take away any one of these, you will see slower plant growth,  a decrease in the plant's productivity, and deficiency illnesses occur.

​If you are interested in improving your crops even more, check out my article that discusses the benefits of plasticulture.

What does each nutrient do for the plant?

Different nutrients have different jobs that they do.  Remember, each nutrient is essential to proper plant growth and development.  Some nutrients are used up while others are reused in the plant.  Keep reading to learn what each nutrient does for the plant.

Primary Macronutrients

Nutrients needed by plants are characterized by macronutrients and micronutrients.  Macro and micro refer to the amount of the nutrient needed by the plant, not the importance of the nutrient.

Macronutrients are then further divided into primary and secondary macronutrients. The primary macronutrients are required in larger quantities than the secondary macronutrients.


Nitrogen is a part of chlorophyll.  Chlorophyll is the green pigment that allows plants to absorb sunlight during photosynthesis.  This means it directly affects the process of photosynthesis.  No nitrogen, no photosynthesis.  Sufficient amounts of nitrogen will allow the plant to continue photosynthesis and experience faster rates of growth.

Nitrogen also affects cellular respiration, which is the process in which the plant uses the energy from photosynthesis and turns it into usable energy for the plant.

Nitrogen is an essential element in all of the amino acids that plants use.  Amino acids are used to make proteins. These amino acids are required to build many plant structures such as cell membranes, chlorophyll and cell tissues.

Carbohydrate formation in the plant is dependent on nitrogen as well.  It is a major component of proteins, hormones, chlorophyll (a major factor in photosynthesis), vitamins and enzymes that are essential for plant life.

Metabolism of nitrogen is a major factor in stem and leaf growth.  Stem and leaf growth is called vegetative growth. Vegetative growth is extremely important in leafy plants such as lettuce or cabbage.  We typically only consume the leaves of these plants, so vegetative development is crucial.

Too much nitrogen can delay flowering and fruiting. Nitrogen impacts crops that produce fruit.  If there isn't adequate nitrogen available for the plant to flower properly, then the plant will be unable to produce fruit.

​Not enough nitrogen can reduce yields, cause yellowing of the leaves, and stunt plant growth.  Nitrogen deficiency is most likely to occur when there are other nutrient deficiencies.  Many other nutrients increase the availability of nitrogen in the plant, so taking these away will increase the likelihood of nitrogen deficiency.

how to fertilize plants properly, tomato plants with nitrogen deficiency


Plants use phosphorus in many processes from photosynthesis, respiration, energy storage, and transfer, cell division, and growth of the plant and plant cells.

​Phosphorus enhances early root formation and development.  Adding phosphorus can improve the quality of fruit, vegetables, and grains that are harvested. Proper seed formation in the plant requires phosphorus.  Plants will use phosphorus to survive harsh winters.

how to fertilizer your plants, lettuce and bok choy surviving the winter because of phosphorus

Also, it will increase the plant's water-use efficiency. A plant's rate of maturity can be increased by adding more phosphorus as well.

Phosphorus is necessary for  protein formation and almost all aspects of growth and metabolism in plants. It is essential for flower and fruit formation. If a plant is in soil that has low pH (less than 4), the soil will chemically lock up the phosphate.  The plant will not be able to use the phosphate.

​If you're growing flowers, like chrysanthemums, phosphorus is essential to keep those beautiful blooms.

flowers of chrysanthemums

Plants that have a phosphorus deficiency will have purple leaves and stems.  They may also have slow growth and take longer to reach maturity. Due to this slow growth, the yields of fruits and flowers will be low. The plants may also drop their leaves and flowers.

​Plants take phosphorus in with their roots.  Phosphorus must be applied close to the roots in order for the plant to absorb it.  If large amounts of phosphorus are applied to the plant without also applying zinc, then the plant may also develop a zinc deficiency.

how to feed your plants with fertilizer, applying fertilizer to plants


Potassium breaks down carbohydrates for energy.  It also moves starches within the plant.  Plants will increase the rate of photosynthesis when potassium is added. It can also help the plant to use water more effectively.  Protein synthesis in plants also requires potassium.

Similar to phosphorus, it is essential to fruit formation, improves the quality of seeds and fruit, and improves winter hardiness.

​Potassium activates and controls many enzymes.  Also, potassium helps the plant fight off diseases.

Secondary Micronutrients


Plants require calcium in order to continue to grow and develop.  Calcium causes cell division and new cell formation.

As I mentioned earlier, plants require large amounts of nitrogen.  Plants use calcium to break down, or metabolize, nitrogen.   If there isn't enough calcium present to metabolize nitrogen that the plant brings in, then the plant could bring in all the nitrogen in the world and not be able to use it if there wasn't calcium there to break it down into a usable form.

Calcium also reduces plant respiration. The plant releases energy during respiration that could have been used to grow fruits and vegetables.

Calcium is important in the fruit formation process.  It helps relocate the energy made during photosynthesis from the leaves to the fruiting organs and also increases the amount of fruit that starts to develop.

​If you have grown tomatoes before, you are probably well aware of blossom end rot. A deficiency of calcium can cause blossom end rot.  Blossom end rot is a disease that creates a dark, rotting area of tissue one the end of the fruit where the blossom was attached.  Hence the name blossom end rot.

fertilizing plants to prevent blossom end rot

It is also essential in many types of nuts for proper nut development.  One example would be peanuts.  Peanut plants are very dependent on calcium to create peanuts.


Magnesium is necessary for the plant to create chlorophyll. Remember,  chlorophyll is the green pigment that captures sunlight so that photosynthesis can take place.  Plants use magnesium to make chlorophyll.

The plant can use phosphorus properly if magnesium is present.  Magnesium also allows phosphorus to move around in the plant. The plant needs to be able to move phosphorus around to different areas of the plant at different times.  Magnesium lets the plant do just that.   Magnesium makes and activates enzymes.

Researchers have linked grass tetany with a deficiency of magnesium in grass. Grass tetany is an illness that is seen in livestock that graze pasture grasses.  The grasses that these livestock graze are low in magnesium, which causes a magnesium deficiency in the livestock as well.  Grass tetany can be fatal to livestock.

Proper amounts of magnesium increase the amount of iron that the plant can use.  Magnesium also helps the plant to mature quicker.  When looking at a group of plants, the maturation of the plants is more uniform when magnesium levels are adequate.


Sulfur has become a more researched nutrient lately, as sulfur deficiencies in soil become more popular.  Because of this, sulfur has often been referred to as the 'fourth primary macronutrient'.

Sulfur is an important part of amino acids.  The plant uses amino acids to build proteins.  About 90% of the sulfur that is taken in by plants is used to create amino acids.

Sulfur also helps to develop enzymes and vitamins. Chlorophyll production requires sulfur to be present.  Sulfur is not a building block of chlorophyll. Plants do need sulfur for proper chlorophyll production.

Sulfur is also necessary in the metabolism of nitrogen.  Remember, nitrogen is one of the nutrients that plants need in large amounts.  If the plant doesn't have enough sulfur to metabolize nitrogen, then the plant could suffer nitrogen deficiencies.

Sulfur aids in proper seed formation.  Click here to read more about the benefits of starting your own seeds at home.

​Sulfur is essential in crops and plants that produce oils.  The oil production process in plants uses sulfur.

Feeding Plants- Micronutrients

Plants require smaller quantities of micronutrients than any of the macronutrients. These micronutrients are still extremely important to plant health even though they are needed in smaller amounts.

Plant health can also be increased by starting seeds yourself.  To read about the benefits of starting your own seeds, click here.


Boron is essential in the germination of pollen grains and the growth of the pollen tubes.  It is also essential for seed and cell wall formation.

Research has shown that boron promotes plant maturity.  Plants that mature faster will provide fruit and vegetables sooner.

Boron is also for sugar translocation. During photosynthesis, the plant makes sugars.  Plants use these sugars as a source of energy.  Plants move sugars around to areas where energy is needed.

The amount of boron in the plant determines the amount of nitrogen that is available to the plant.  Low amounts of boron can lead to nitrogen deficiencies.


There is little known about chlorine and its functions in the plant. However, it is known that the amount of phosphorus absorbed by the plant is affected by the amount of chlorine present.

It also enhances maturity of small grains in certain environments.


Several processes in the plant are sped up with copper.  It has major involvement in photosynthesis and plant reproduction.  Copper indirectly produces chlorophyll.

Copper increases sugar content, intensifies plant color and improves the flavor of fruits and vegetables.  Plants can benefit from increased amounts of copper.  They will have deeper color and produce more fruits and vegetables.


Iron helps start the process of making chlorophyll.

It also acts as an oxygen carrier in the plant.  We typically think of plants requiring carbon dioxide, not oxygen.  Cellular respiration requires oxygen.  Photosynthesis makes energy for the plant.  However, this energy is not in the form that plants need.  The plant uses cellular respiration to make usable energy.  Cellular respiration takes the energy made in photosynthesis and converts it into a type of energy that the plant can use.

​Many reactions that take place during cell division and growth require iron to take place.


Some enzyme systems in the plants use manganese.  Enzymes speed up chemical reactions.  Faster chemical reactions mean faster growth and development.  During photosynthesis, chlorophyll absorbs energy from sunlight.  Plants use manganese to make chlorophyll.

​Increased amounts of manganese increase the amount phosphorus and calcium that the plant can use.  The plant needs large amounts of calcium and phosphorus.  Manganese could help prevent phosphorus and calcium deficiencies by increasing the amounts available.


An enzyme exists in plants that takes nitrates and turns them into ammonium.  Molybdenum makes that enzyme.  The plant doesn't use nitrates, but it does use ammonium.   Most plants prefer to use nitrogen in the form of ammonium, so molybdenum helps create more usable nitrogen.

Plants will use molybdenum to make phosphates that it can use.  Plants cannot use all types of phosphates, only certain kinds.  Molybdenum helps create the usable forms of phosphates for the plant.


​Zinc is another nutrient that is necessary for chlorophyll production, carbohydrate formation, and starch formation.  It also aids the plant in producing growth hormones and supporting the enzyme system.  Zinc also aids in seed formation.

Final thoughts about feeding plants

I know I just threw a ton of information at you.  BUT, I wanted you to realize that all of these nutrients are important for plants.  Especially if you want productive plants!

Next time you pick up a bag of fertilizer, look over the label.  Make sure that you're buying a quality fertilizer that includes these nutrients.  If you purchase a fertilizer that has just nitrogen, phosphorus, and potassium (which is really easy to do), then you may be shorting your plant some of the other micronutrients that they need.

Remember, many of the macronutrients that are needed by the plant are only available if there are micronutrients present.   If you've been applying fertilizer and the plants are growing slowly, start losing flowers and fruit, or the leaves start yellowing unexpectedly, then you may have a deficiency that is caused by low amounts of micronutrients.

Use this information to make sure that you are feeding your plant all of the nutrients it needs to be happy and healthy.  You can also use this information if you are nutrition or food savvy.  This information could help you create nutrient-dense compost for your plants if you make your own compost.

For example, bananas are high in potassium.  Plants need large amounts of potassium.  You can use leftover banana peels to feed your plants potassium.  Or, if you compost, add the banana peels to the compost so that the compost will be rich in potassium.

You can help make sure that your plants are well-fed by ensuring that the soil stays rich.  Here's a list of three things that you can do in the fall to help your soil.

​Remember, healthy plants are productive plants!

​If you haven't yet, grab your FREE copy of the From Seed to Supper guide and learn how to start growing delicious, fresh vegetables and herbs!

fertilizing plants, free guide to growing more food at home

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