Nutrient Deficiencies In Plants (How To Identify)

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As a home gardener or indoor grower, it’s a good idea to monitor the leaves of your plants. It’s the best way to stay on top of issues and recognize whether your plant is struggling.

You can use leaves as a starting point to help determine if your plant has a nutrient deficiency.

Note: It is difficult to identify nutrient deficiencies by appearance alone, and a soil test is always recommended for proper diagnosis.

There are many factors that can cause visual symptoms resembling nutrient deficiencies. Environmental conditions like drought, pests, exposure to herbicides, and disease are all examples of things that can stress your plant and alter the appearance of the leaves.

After you’ve ruled out other causes, you may want to consider nutrient deficiencies as the culprit.

Nutrient Deficiency Flowchart

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    Where do you start?

    When a plant has a nutrient deficiency, symptoms will show up on either old or new leaves, depending on how mobile the nutrient is. This is a great place to start when trying to identify nutrient deficiencies in plants.

    • Deficiencies of a mobile nutrient, like nitrogen or phosphorus, will first show on older leaves. The old leaves act as a nutrient reservoir, providing resources and nutrients for new leaves. As the plant prioritizes new growth, it pulls nutrients from older tissues.
    • Deficiencies of an immobile nutrient, like calcium or iron, will first show on the newest growth. This is because immobile nutrients cannot easily move around the plant. So, the nutrients cannot be scavenged from those older leaves.

    Remember: Other issues such as disease and drought can be misinterpreted as a nutrient deficiency. So, keep this in mind when diagnosing your plant.

    Why you should address a nutrient deficiency

    Every process that takes place in a plant requires specific nutrients. Even one nutrient being in short supply is enough to restrict growth and productivity. The nutrient that is most scarce in an environment is referred to as “the limiting factor.”

    Imagine if you were baking a cake, and you had all of the ingredients on hand except for eggs. No matter how much flour or sugar you had, you can’t make that recipe properly without the eggs. Similarly, plants need many different nutrients to thrive. If one nutrient is deficient, it becomes the limiting factor, restricting the plant’s development.

    Remember: Addressing a nutrient deficiency is not always about adding more of the deficient nutrient. Sometimes, it involves managing other factors, like your watering habits or the pH of your soil, to improve nutrient availability.

    Generally speaking, it is more likely that your houseplants or container plants will have a nutrient deficiency. Plant roots are very good at scavenging the soil for what they need when planted directly in the ground.

    Nitrogen deficiency in plants

    Nitrogen is the most commonly deficient nutrient. This nutrient is not held in the soil for very long, and it is used in large quantities by actively growing plants. It is a mobile nutrient, so it will move out of older leaves into new growth as supply runs low. The older leaves will become uniformly chlorotic (yellowing of the leaves), and then eventually die off.

    Nitrogen deficiency in plants
    Nitrogen deficiency in pepper plants

    Note: Some plants, like brassicas, may show a reddish pigment in their older leaves when a nitrogen deficiency is present.

    How to treat: Most plants will recover quickly from a nitrogen deficiency after fertilizer is applied. Using a synthetic fertilizer will provide the quickest feed.

    Phosphorus deficiency in plants

    More often, there is an excess of phosphorus in the soil, making phosphorus deficiency a rare issue in the garden. Typically, phosphorus deficiencies occur because the plant cannot effectively uptake the nutrient, rather than there being a true soil deficiency.

    Phosphorus deficiency on leaves
    Phosphorus deficiency on tomato plant.

    Plants will respond to this stress by producing more anthocyanins. A reddish-purple color on older leaves can indicate a phosphorus deficiency. New growth may not be discolored, but the leaves might be smaller than normal.

    Note: Excess sun exposure can also cause purple leaves, though this discoloration is more often seen on newer growth rather than older leaves.

    How to treat: Be mindful of temperatures, as cold air or soil temperatures can make it more difficult for nutrient uptake. Plants may also have difficulty accessing phosphorus if the soil pH is too acidic or too alkaline. Treat with phosphorus fertilizer if growing in containers or a soil test indicates a deficiency.

    Potassium deficiency

    Potassium deficiency is also not very common for the home garden. Yellow or brown discoloration on the tips and leaf edges of older leaves may indicate a potassium deficiency. You may also see a metallic/bronze sheen on the leaves of your plant or necrotic dead spots.

    Potassium deficiency in plants
    Potassium deficiency showing non-uniform chlorosis and brown spots – Photo credit: Alandmanson / Wikimedia

    Yellowing is typically non-uniform, with the leaf veins of the plant remaining green as the tissue surrounding the veins turns yellow (interveinal chlorosis).

    How to treat: Be mindful of your watering habits. Increased soil moisture helps to facilitate potassium uptake. Treat with potassium fertilizer if needed.

    Magnesium deficiency in plants

    Magnesium is a mobile nutrient necessary for the production of chlorophyl. Deficiency causes interveinal chlorosis on older leaves. Chlorosis begins at the tips of the older leaves and eventually progresses towards the center of the leaf while the veins remain green. You may also see small brown spots or leaves curling upward.

    Magnesium deficiency in plants
    Magnesium deficiency

    Too much potassium can also inhibit the uptake of magnesium and cause a deficiency in the plant. This is sometimes seen in tomato plants when gardeners use tomato fertilizers high in potassium.

    How to treat: Epsom salts are an easy way to treat a magnesium deficiency in the garden. However, many people add epsom salts to their garden without really knowing the reason. We only recommend this if you are sure you have a magnesium deficiency.

    Calcium deficiency in plants

    Calcium is an immobile nutrient, so deficiencies will show up on the newer, youngest leaves. A calcium deficiency can also manifest as blossom end rot.

    Blossom end rot on tomato
    Blossom end rot on tomato.

    Blossom end rot: A common issue that occurs in the garden when plants are deficient in calcium. This can be due to lack of calcium in the soil, but more frequently occurs due to irregular watering. Lack of water interferes with the availability of calcium to the plant and adding calcium will not fix the issue.

    How to treat: Be mindful of the pH of your soil. If your soil is acidic, you can add lime as well as calcium and magnesium. Stick to consistent watering to keep the soil evenly moist at all times, and add mulch to improve soil water retention.

    Sulfur deficiency in plants

    This deficiency is more common with acidic soils. Newer leaves will grow in pale and yellow, while older leaves remain green.

    How to treat: This deficiency can be treated with epsom salt.

    Iron deficiency in plants

    Iron deficiency manifests as interveinal chlorosis of new leaves and often affects acid-loving plants (like blueberries). In alkaline soils, iron becomes unavailable and the plants will show interveinal chlorosis on young leaves. Adding iron will typically not resolve this situation, as the pH of the soil needs to be addressed to correct this.

    Iron deficiency in plants
    Iron deficiency on new growth leaves.

    ‚ÄčAs I mentioned, it is very difficult to determine if a plant has a nutrient deficiency solely based off the appearance of the leaves. It’s important to consider your plant, as well as your soil, before taking action. It’s best to consider all factors that may be affecting your plants leaves or growth!

    I recommend a professional soil test if you are gardening in an in-ground bed. These tests are typically inexpensive and can provide a wealth of knowledge. I hope this guide helps you to better diagnosis what may be happening with your plants at home.

    One Comment

    1. I’ve been having issues with people leaves on my corn and pole beans. I thought it was temperature at first due to some abnormally cold days but I’m concerned for my pole beans. Any suggestions ?

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