The majority of the nutrients a plant needs is absorbed through the soil solution (moisture held in between soil particles). Plants can only grow to their full potential if everything they need is present in this solution. Outside plants are continually fed naturally, either by growing deeper roots or external activity (such as animal excrement or rotting wood or food). Indoor plants periodically deplete their soil of nutrients. Without your intervention, they will thrive less.
When you fertilize your plants, you are replenishing their soil with nutrients. There are 17 elements that are needed for a plant to be healthy and thrive. In this article, we will name each element and explain how it helps your houseplant.
Basics of Photosynthesis
The action of a plant converting air and water into sugars for food is called photosynthesis. Part of the process of photosynthesis includes the plants releasing oxygen after consuming carbon dioxide. The core elements of this process are carbon, hydrogen, and oxygen. Photosynthesis also requires energy from the sun.
| Element | Part Affected | Deficiency Symptom | What it Does | Additional Notes |
|---|---|---|---|---|
| Carbon (C) | Whole Plant | N/A | Promotes healthy growth in the plant | Essential for photosynthesis |
| Hydrogen (H) | Whole Plant | N/A | Promotes healthy growth in the plant | Helps release oxygen into the air |
| Oxygen (O) | Whole plant | Stunted plant | Used for respiration in the plant | Extra produced oxygen is released into the air |
These three elements are not considered nutrients, but they are necessary for the plant to survive. Plants absorb them in large quantities through water and the carbon dioxide in the air.
Primary Nutrients for Houseplants
The six primary nutrients for houseplants are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. The first three are generally known as the N-P-K ratio. The latter three are generally known as secondary nutrients.
What is the N-P-K ratio?
The N-P-K ratio is listed on most purchased fertilizers. The bag (or box) will have three numbers listed, such as 10-30-10. The first number represents the percentage of nitrogen content, the second number represents phosphorus, and the last number represents potassium.
The N-P-K ratio helps houseplant owners to determine which fertilizer to purchase for their plants as different varieties need different ratios of nutrients.
Nitrogen, Phosphorous, and Potassium
These three macronutrients each function in a way to improve the overall health of your plant. When purchasing fertilizer for your greenery, take special note of these three elements over anything else. What do these nutrients do?
| Element | Part Affected | Deficiency Symptom | Elemental Role | Additional Notes |
|---|---|---|---|---|
| Nitrogen (N) | Leaves, plant tissue | Slow growth, yellowing leaves (starting with older leaves) | For healthy foliage growth, aids in photosynthesis | Can be washed away during watering |
| Phosphorus (P) | Roots, fruits, buds/flowers | Slow growth, abnormal dark green or purplish stems and leaves | For healthy root growth, helps produce flowers and fruit | Too much phosphorus can inhibit the plant from getting zinc, manganese, and iron |
| Potassium (K) | Buds/flowers, leaves, fruit | Dry or yellowish leaves, smaller developed flowers or fruit | Catalyzes enzymes, promotes bigger blooms, opens and closes stomata, helps the plant resist disease | Too much potassium can inhibit the plant from getting other nutrients. |
Why Do Plants Need Nitrogen?
The building blocks of all proteins, amino acids, are made up of an amino group of nitrogen and hydrogen(―NH2), a carboxyl group of carbon, 2 oxygen and hydrogen (―COOH), and an organic R group (which will vary). Amino acids are important for the production of new tissue. In plants, we see it in new, healthy foliage growth. Plants with a proper balance of nitrogen will have the correct green hue in the pigment of their leaves.
Nitrogen also aids in photosynthesis as it is a major compound that makes up chlorophyll (C55 H72 O5 N4 Mg), which allows plants to absorb energy from the sun.
What Plants Benefit Most from Nitrogen?
As nitrogen supports the healthy growth of leaves, it is especially important for leafy plants. If you notice that your houseplant’s leaves are growing slower or are turning yellow, it could be from a nitrogen deficiency. The following are a few kinds of plants that generally benefit from a nitrogen-heavy fertilizer:
- Dieffenbachia
- Ficus
- Ivies
- Grasses
- Philodendrons
Symptoms of Nitrogen Deficiency in Plants
If a plant lacks nitrogen (which means it will lack chlorophyll), it will fail to use the sun as a source of energy, leading to a breakdown of essential functions. The older tissues will be affected first. You may see some older leaves begin to fade or turn yellow. New growth will be stunted and slow. To increase the nutrient uptake again, you need to add nitrogen (and/or phosphorus) to your soil.
Potential Problems From Too Much Nitrogen in Indoor Plants
There are a couple of negative side effects when too much nitrogen is present:
- If you give too much nitrogen to a plant that generally blooms, it may produce fewer fruits or flowers (or none at all).
- Nitrogen can wash away easily. With houseplants, this is a minimal problem as another greenery is unlikely to be affected. Outdoors, however, there have been environmental issues involving nitrogen (and phosphorus) wash-offs, including substantial issues with some parts of the ocean.
Why Do Plants Need Phosphorus?
Phosphorus aids in the transfer of energy from one part of a plant to another. It is one of the major factors in helping your plant’s buds develop and bloom. When purchasing fertilizer for flowering or fruiting plants, look for one that has a higher amount of phosphorus.
These plants may include:
- African Violets
- Begonias
- Gloxinia
- Jasmine
- Lilies
Symptoms of Phosphorus Deficiency in Plants
If the stems and leaves of your houseplant start to turn very dark green or gain a purplish tint, it may be due to a lack of phosphorus. These plants might also experience stunting in their growth.
If the soil it too cold or the pH balance is wrong, the plant might not be able to get the phosphorus it needs, even if there is phosphorus present.
Potential Problems From Too Much Phosphorus in Indoor Plants
Too much phosphorus in plants can cause potential problems. In household plants, too much phosphorus can interfere with the amount of iron, zinc, and manganese that your plants can absorb. While these are micronutrients, plants need them to thrive as well.
Outdoors, too much phosphorus could potentially lead it to be washed away, which could cause pollution.
Why Do Plants Need Potassium?
Potassium (also known as potash) improves the vitality and strength of your plants. It helps flowering varieties develop bigger and healthier blooms. Potassium helps the plant catalyze enzymes which helps the plant grow through protein synthesis.
The element is also important for the stomata (small opening on the leaves which help the plant “breathe”), as it regulates when the stomata open and closes. Potassium can also help your plant resist some diseases.
Symptoms of Too Much Potassium in Plants
Without potassium, the plant won’t be able to get the nutrients it needs from the water and air, resulting in a dried-out plant.
Potential Problems From Too Much Potassium in Indoor Plants
Don’t feed your plant too much potassium, however. Like phosphorus, too much potassium can block the plant’s ability to get other nutrients it needs for survival.
Secondary Macronutrients for Your Houseplants
As stated above, calcium, magnesium, and sulfur are the secondary macronutrients that your houseplant needs. These three elements are generally added to garden or potting soil but may need to be added over time.
| Element | Part Affected | Deficiency Symptom | Elemental Role | Additional Notes |
|---|---|---|---|---|
| Calcium (Ca) | Cells in leaves, flowers, fruit, and roots | Deformed/abnormal leaves, flowers, and fruit. Stunted growth in the plant and in the root system | Maintains chemical balance in the soil, neutralizes cell acids, metabolizes carbohydrates | While calcium is found in many minerals in soil, the plant can’t always use those minerals for the calcium it needs |
| Magnesium (Mg) | Leaves, roots, and systems | Discolored leaves (most often yellow, but can also redden or brown) | A component of chlorophyll, stabilizes membranes, helps with metabolism | Might not be absorbed if there is too much potassium in the soil |
| Sulfur (S) | Roots, seeds | Younger leaves are yellowing | Important for root and seed production, reduces sodium in soil | Deficiency looks similar to nitrogen deficiency |
Why Do Plants Need Calcium?
Every plant must have calcium in order to grow and thrive. It is a component that makes up the cell walls and it cannot be reused from older tissue when calcium supply runs low. Calcium is a necessary part of several physiological and metabolic processes.
When experiencing calcium deficiency, the plant can exhibit a variety of problems such as abnormalities in the flowers or fruit, deformed or discolored leaves, and stunted growth in both the plant and its root systems. The plant needs calcium in its tissues to avoid these problems. Calcium in the soil can’t always be accessed by the plant.
Rarely will a plant have “too much calcium.” In those cases, the calcium could prohibit the plant from taking and utilizing other nutrients.
Why Do Plants Need Magnesium?
Magnesium is absorbed through the roots of the plant. It is a key component of chlorophyll and is essential for growth through photosynthesis. Magnesium is one of the elements that make the leaves of a plant green. The element helps stabilize cell membranes and is necessary for the plant to metabolize carbohydrates.
If a plant doesn’t have the magnesium it needs, the leaves will begin to discolor on the edges and between the veins. They generally turn yellow, but can also turn brown, red, or purple. If no action is taken to restore magnesium to the soil, the plant will die.
If you are frequently adding fertilizer or compost to your plants, you shouldn’t have any problems.
Why Do Plants Need Sulfur?
Sulfur is important for seed production and the overall growth of the plant and root system. It also reduces sodium in the soil. Sulfur is also essential in giving some plants their flavor. These include onions, garlic, and mustard.
If your soil doesn’t percolate enough in between fertilization, you may experience a rare sulfur deficiency. If you have yellowing leaves, you may have a sulfur deficiency, though the discoloration is more likely due to a lack of nitrogen. The way you can tell the difference is by looking at the age of the leaves. If it is the older leaves that are yellowing, it is due to nitrogen deficiency. Younger leaves yellowing points toward sulfur deficiency.
The Micronutrients Your Houseplants Need
While these nutrients are not needed in large amounts, they are still important for the overall health of your plant. With the secondary macronutrients, these elements will help your plant’s metabolism and encourage healthier growth. When adding soil, check the “ingredients” to see which nutrients are missing.
Micronutrients include Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Zinc, and Nickel. As researchers discover more about our plants, more could be added to this list.
| Element | Part Affected | Deficiency Symptom | Elemental Role | Additional Notes |
|---|---|---|---|---|
| Boron (B) | Cell walls, pollen/seeds, roots | Stunted growth, including root elongation, failure to flower or seed | Enables membrane function, and primary component of cell walls | Helps rid the plants of aluminum toxicity |
| Chlorine (Cl) | Enzyme systems, stomata | Blotchy or wilting leaves, stunted growth | Regulates moisture release from the stomata, aids energy reactions for enzyme systems | Actually the chlorine anion (Cl-), generally comes from volcanic emissions, marine aerosols, and salt |
| Copper (Cu) | Enzyme systems | Newer leaves are shorter and have spotting on the leaf margins | Helps with photosynthesis and plant growth | Helps some vegetables get their flavor |
| Iron (Fe) | Whole plant | Leaves and stems will lose their green color and turn sickly yellow | Important for photosynthesis and chlorophyll production | Too much alkaline and lime could potentially lead to iron deficiency |
| Manganese (Mn) | Whole plant | Leaves will yellow and sometimes curl | Enables metabolism of carbohydrates and nitrogen | Use manganese sulfate on soil to balance the deficiency |
| Molybdenum (Mo) | Whole plant | Edges of leaves will yellow and curl | Metabolizes nitrogen | Deficiency can be caused by nitrate-heavy fertilizers |
| Nickel (Ni) | Whole plant | Only visual under extreme deficiency, necrotic lesions on leaf tips | Metabolizes nitrogen, helps the plant to grow, protects against disease | Usually found in contaminants in water, soil, and fertilizer |
| Zinc (Zn) | Enzyme systems | Yellowing leaves between green veins, affects the lower part of the plant first. | Stabilizes enzyme systems and important for growth hormones | No adverse side effects for “too much zinc” |
Why Do Plants Need Boron?
Boron is a necessary component of cell wall formation. It also transfers energy to new growth and helps membranes function correctly. Boron is essential for both quality pollen and seeds as well as root growth. Boron also helps the plant uptake potassium and phosphorus, colonizes roots, and rids plants of aluminum toxicity.
If your plant has a boron deficiency, the pollen won’t be as vital and you are likely to get fewer flowers per plant. You can typically notice the deficiency in newer growth as well. If the plant won’t flower (or flowers less than usual) or if you notice stunted growth, it may stem from less boron.
Why Do Plants Need Chlorine?
Chlorine is used in energy reactions in the plant and is used to activate many enzyme systems. It isn’t necessary in large quantities, but it is needed by every plant. It is often left off of lists of houseplant nutrients.
Chlorine regulates moisture release from plants through the stomata. This way, the plant can protect itself in dry periods from losing too much water. Without chlorine, the plant would be unable to acclimate to different weather conditions very well.
Leaves may begin to wilt or become blotchy if the plant doesn’t have enough access to chlorine. Too much chlorine can also lead to necrosis along the margins of leaves or stunted growth on both the leaves and the plant.
Why Do Plants Need Copper?
Though copper is only needed in small quantities, it is also very essential to a plant’s growth. It helps form chlorophyll. Copper is necessary for photosynthesis and aids many enzyme processes.
The element helps the plant metabolize carbohydrates and proteins. Copper is also responsible for some of the flavors in some vegetables, as well as the color of many veggies and flowers.
When a plant has a copper deficiency, it will show up in newer parts of the plant. You will notice cupping within new leaves, and small spots may appear on the margins. New leaves will be smaller in size and may wilt. The color of flowers or veggies may not be as vibrant as usual.
Too much copper can hurt the root system by burning the tips. It can also stop the plant from getting some of the other necessary ingredients to thrive. Eventually, the plant will begin to fail and ultimately die.
Why Do Plants Need Iron?
Iron is necessary for photosynthesis and the production of chlorophyll. It carries other elements to the parts of the plants that need the nutrients. Iron helps the plant get the oxygen it needs.
Plants that are lacking iron will start to lose the green in their leaves and turn a sickly yellow. If you add too much alkaline or lime to your soil, it could cause an iron deficiency. Add iron or sulfur to even out the pH balance.
Why Do Plants Need Manganese?
Manganese is essential for the metabolism of nitrogen and carbohydrates in plants. It is important for the formation of a chloroplast as well as enzyme synthesis.
A plant can face serious issues if it doesn’t have enough manganese. As manganese is essential to photosynthesis, leaves will yellow and occasionally curl. You can generally see these symptoms on younger leaves first. Add manganese sulfate to the soil to help minimize issues of deficiency. Make sure to dilute it and water the plant first.
Why Do Plants Need Molybdenum?
Molybdenum is needed in the smallest quantity for plants. It metabolizes the nitrogen by converting nitrate into nitrite, then into ammonia. Ammonia is used to synthesize the plant’s amino acids. Molybdenum can also convert inorganic phosphorus into an organic substance.
A molybdenum deficiency is very rarely seen. It is most common in poinsettias, where the leaf margins will be yellow and curl. The deficiency could mimic a nitrogen deficiency as these two elements are linked. Some leaves will turn yellow. Molybdenum deficiency will affect the whole plant. A nitrate-heavy fertilizer may lead to a molybdenum deficiency far faster than other fertilizers.
Why Do Plants Need Nickel?
Nickel is vital to a plant’s growth. A plant generally gets enough nickel from contaminants in water, fertilizer, and soil. Nickel is a part of some enzymes in the plant, including urease, which metabolizes urea nitrogen into ammonia that the plant can use. It is theorized that Nickel also helps plants tolerate the disease.
The deficiency of Nickel is rarely seen and is often misdiagnosed. There are no visual symptoms seen on plants unless there is a significant deficiency. In those cases, it will involve necrotic lesions on older leaves along with the leaf tips. New growth may be stunted and change the overall appearance of the plant.
Why Do Plants Need Zinc?
Zinc is a nutrient that is essential for the plant’s enzyme systems and growth systems. It helps the plant produce chlorophyll.
If your plant has a zinc deficiency, it may develop chlorosis, a specific type of leave discoloration. While the veins on the leaves will remain green, the parts between them will be yellow. The discoloration appears on older, lower leaves first, then will gradually move to newer leaves. As the newer leaves begin to discolor, older leaves will usually turn purplish or brown, then ultimately die. While it is impossible to truly know if it is zinc your soil is lacking without a test, zinc deficiency generally affects lower leaves first, while other elements will affect higher or newer leaves first.
There are no real negative side effects to exposing a plant to more zinc than it needs. Therefore, if you expect a deficiency, spray your plants with kelp extract or another spray containing zinc. If it was a zinc deficiency, your plant should recover very quickly.