A hydroponic nutrient deficiency chart is only useful if you read it the right way round. Most charts list a dozen nutrients and a dozen symptoms, and nearly every symptom on them is some shade of yellow. The trick that makes them readable is simple: look at where on the plant the problem starts before you look at what it looks like. That one question cuts the list in half.
This guide gives you that chart for the nutrients that matter, with the symptoms taken from university extension guides. It also explains the part most charts leave out: in hydroponics, a leaf that looks short of a nutrient usually isn’t short of anything in the water. If you are just starting out, the complete guide to apartment hydroponics covers the basics first.
How to Read a Nutrient Deficiency in Hydroponics
Work through three questions, in this order:
- Where does it start? On the oldest, lowest leaves, or on the newest growth at the top?
- What does it look like? An even pale green, yellow between the veins, purple tints, or brown, scorched edges?
- What do the meters say? A pH out of range or an EC that is too low or too high explains most of what you see.
Then fix the pH and the strength before you add anything. A complete hydroponic nutrient already contains every element on the chart, so the cure is usually getting the existing nutrients into the plant rather than buying a new bottle.
Key takeaways
- Symptoms on old, lower leaves point to nutrients the plant can move: nitrogen, phosphorus, potassium and magnesium.
- Symptoms on new growth point to nutrients that stay put, such as calcium, iron, manganese, zinc and boron.
- A pH out of range locks nutrients out even when they are in the water, so measure it first.
- Too much fertilizer can look like too little, with burnt edges and wilting despite plenty of water.
- Judge any fix on new growth, since leaves that are already damaged rarely recover.
Old Leaves or New Growth?
Plants can move some nutrients around and not others. Cornell’s nutrient tables class nitrogen and potassium as mobile inside the plant, with phosphorus and magnesium somewhat mobile. When one of these runs short, the plant pulls it out of its oldest leaves to feed new growth, so the lower leaves show the shortage first while the top stays green.
Calcium, iron, manganese, zinc, copper and boron are the opposite: Cornell lists them as immobile. Once they are in a leaf, they stay there, so the plant can’t rescue new growth from old leaves. That is why a shortage of any of them shows up on the newest leaves and growing tips first, while the old leaves look fine.
So before you compare colors, note which end of the plant is affected. A yellow bottom leaf and a yellow top leaf are two different problems, even when the yellow looks the same.
The Hydroponic Nutrient Deficiency Chart
Each symptom below comes from the University of Arizona’s guide to nutrient deficiency symptoms and Penn State Extension’s hydroponics guide. The last column is the first thing to check in a hydroponic system, because that is where the cause usually lies.
| Nutrient | Starts on | What you see | Check first |
|---|---|---|---|
| Nitrogen | Older leaves | Older leaves yellow while the whole plant goes pale and stunted | EC too low |
| Phosphorus | Older leaves | Burnt-looking tips, then dark green or purple older leaves | pH |
| Potassium | Older leaves | Scorched edges, with yellowing that works inward from the margins | EC and solution age |
| Magnesium | Lower to middle leaves | Yellow between the veins while the veins stay green | pH |
| Calcium | New growth | Brown edges on new leaves, so tipburn in lettuce and blossom end rot in tomatoes | pH and airflow |
| Sulfur | Younger leaves | Younger leaves turn yellow first | Nutrient label |
| Iron | New growth | Yellow between the veins of the newest leaves | pH too high |
| Manganese | New growth | Yellow between the veins, but less distinct than iron, with dead spots | pH |
| Zinc | New growth | Crowded, rosette-like new leaves, yellow between the veins | pH too high |
| Boron | Growing tips | Growing tips die back, so side shoots bunch up below them | Nutrient label |
Copper and molybdenum shortages are rare. Arizona describes copper deficiency as dark green, stunted plants, while molybdenum deficiency mimics nitrogen deficiency on the older leaves. In a home system running a complete nutrient, though, you are unlikely to meet either.
Notice how often “pH” appears in the last column. That is not a shortcut; it reflects how hydroponics works. The hydroponic pH and EC chart has the right range for every crop, so check your numbers against it before changing anything else.
Check These Before Adding Anything
Hydroponic systems are less forgiving than soil, Penn State notes, and nutrient problems show up quickly. The good news is that the causes are few, and you can rule most of them out with two meters in a few minutes.
1. The pH
An out-of-range pH stops roots taking up nutrients that are sitting right there in the solution. Penn State gives a high pH as the most common cause of iron deficiency, and lists it among the causes of magnesium deficiency too, while a low pH can cause calcium deficiency. Most herbs and greens on this site run at pH 5.5 to 6.5. If yours has drifted, why pH keeps drifting explains the usual reasons, and the pH meter roundup covers pens worth trusting.
2. The EC
EC measures how strong the nutrient solution is. Penn State recommends monitoring it to prevent nitrogen deficiency, the pale, yellowing plant at the top of the chart, since under-feeding is its usual cause. On the other hand, an EC that runs too high causes salt damage, which the next section covers. The EC meter roundup compares pens, while EC for hydroponic herbs gives each herb’s target.
3. The Balance and the Age of the Solution
Plants take up nutrients at different rates, so an old solution drifts out of balance even when its EC still looks right. Too much of one nutrient can also block another, which Penn State calls antagonism. Its examples include excess potassium blocking nitrogen, calcium and magnesium, and excess calcium blocking magnesium and boron. So a plant can be deficient in a nutrient that is present in the water.
The cure for both is the same: a fresh batch, mixed at the right strength from a complete nutrient. How often to change hydroponic water has the schedule, and mixing two-part nutrients shows the order that keeps the parts from reacting. The pH and nutrient calculator sizes the batch for your container.
4. Your Water
Very soft, filtered or RO water carries almost no calcium or magnesium of its own, so a nutrient that relies on the water for some of them can come up short. Hard tap water, by contrast, can push the pH up. Using tap water for hydroponics explains how to find out what yours carries, and whether you need Cal-Mag covers the soft-water case.
When Too Much Looks Like Too Little
Fertilizers are salts, and too much of them causes its own damage. Penn State describes the symptoms of excess soluble salts as wilting even though the plant has plenty of water, dark green foliage, dead and burned leaf margins, and dying roots. The University of Arizona adds the typical pattern of salt burn: browning that starts at the leaf tip and runs along the edges, separated from the green by a thin yellow halo.
Because burnt edges also appear under potassium and calcium on the chart, it is easy to read salt burn as a shortage and add more nutrient, which makes it worse. So if the EC reads high, bring it down before anything else; lowering EC in a small system shows how to do it gently.
Boron deserves its own warning. Penn State notes that of the nutrients commonly applied as fertilizer, boron has the narrowest range between deficiency and toxicity, and toxicity shows as yellow and dead spots on leaf margins. Never add boron on its own to a home system; a complete nutrient already carries the right trace amount.
Problems That Only Look Like Deficiencies
Several common problems produce yellow or brown leaves without any nutrient being involved. Rule these out too:
- Root problems. Brown, slimy roots can’t take up anything, so the whole plant looks starved. Preventing root rot shows what healthy roots look like.
- Light burn. Bleached or yellow patches on the top leaves, closest to the light, usually mean the light is too close; see grow light burn.
- Pests. Fine pale speckling on leaves, often with webbing underneath, is spider mite damage rather than a deficiency, as spider mites on hydroponic herbs shows.
- Cold. Cold water slows a plant down until it looks pale and hungry, which is why hydroponics in winter starts with the root zone temperature.
- Old age. The very lowest leaves of a mature plant yellow and drop on their own. One or two old leaves going yellow while everything else grows well is normal.
The yellow leaves guide walks through all of these causes in order, starting from the most likely.
Signs to Know on Common Crops
A few deficiencies turn up again and again on the crops people grow most at home.
- Lettuce tipburn. Brown, dry edges on the inner, newest leaves are calcium deficiency, and Penn State ties it to airflow as much as to the nutrient. Still air slows the water flow that carries calcium into new leaves, so a gentle fan helps; the countertop lettuce guide covers the setup.
- Blossom end rot in tomatoes and peppers. A dark, sunken patch on the bottom of the fruit is calcium deficiency too, according to Penn State; see growing cherry tomatoes indoors.
- Yellow tops on basil. Yellowing between the veins of basil’s newest leaves is the classic iron picture. Penn State shows a basil crop where new growth came back green once iron reached the water, which is also why a high pH is the first suspect; the complete basil guide has its pH and EC.
- Yellow between the veins on lower leaves. This is the magnesium pattern, on any crop. Epsom salt in hydroponics explains when extra magnesium helps and how much to add.
Fixing a Deficiency, Step by Step
- Measure the pH and bring it into the crop’s range.
- Measure the EC and compare it with the crop’s target on the chart.
- Look at the roots. White and firm is good; brown and slimy is a root problem, not a nutrient one.
- Mix a fresh batch of a complete nutrient at the right strength if the solution is old, weak or too strong.
- Wait a week and judge the new growth. Damaged leaves rarely turn green again, but healthy new leaves mean the fix worked.
- Only then consider a supplement, and only for the nutrient the pattern points to, such as Cal-Mag for soft water or Epsom salt for a magnesium gap.
When the Fertilizer Is the Problem
If you are using a fertilizer made for soil, it may be the cause rather than the cure: why Miracle-Gro doesn’t work in water explains what such fertilizers leave out. A complete formula avoids most of this chart in the first place, and the best hydroponic nutrients for small systems compares them.
Where these facts come from
🔗 Where this comes from Deficiency causes, symptoms and cures for nitrogen, calcium, iron and magnesium, the soluble salts and boron warnings, and the antagonisms are from Penn State Extension’s guide to essential nutrients in hydroponics. Symptoms for phosphorus, potassium, sulfur, manganese, zinc, boron, copper and molybdenum, and the salt burn pattern, are from the University of Arizona’s guide to symptoms of plant nutrient deficiencies. Which nutrients move inside the plant is from Cornell’s nutrient management competency notes. The pH range is this site’s standard for herbs and greens.
Tip. Write down the pH and EC every time you check, along with the date and what the plant looks like. A pattern that builds over two weeks is far easier to read than a single reading, and the free hydroponics tracker keeps the log for you. The seed-to-harvest calculator then shows whether a slow patch has cost you any time.
One Last Tip
When a leaf changes color, the meters come out before any bottle does. Nine times out of ten the pH has drifted or the solution has got old, and a fresh batch at the right pH fixes it within a week of new growth. Supplements are for the tenth time, when the numbers are right, the roots are white, and the pattern on the chart still points at one nutrient.
Frequently Asked Questions
How do I identify a nutrient deficiency in hydroponics?
Start with where the symptom appears. Problems on old, lower leaves point to nitrogen, phosphorus, potassium or magnesium, while problems on new growth point to calcium, iron, manganese, zinc or boron. Then check the pH and EC, because an out-of-range reading causes most deficiencies in hydroponics.
Why are the bottom leaves of my hydroponic plant turning yellow?
Even yellowing of the lower leaves with a pale plant overall usually means nitrogen is short, often because the EC is too low or the solution is old. Yellow between the veins of lower leaves points to magnesium. One or two of the very oldest leaves yellowing on a healthy plant is normal aging.
Why are the new leaves yellow on my hydroponic plant?
Yellowing between the veins of the newest leaves is the typical sign of iron deficiency, and Penn State gives a high pH as its most common cause. Manganese and zinc look similar. Bring the pH into range first, then judge the next week of new growth.
What are three symptoms of a nutrient deficiency?
The most common are yellowing leaves, either all over or between the veins; brown, scorched leaf edges or tips; and stunted, slow growth. Purple or very dark green older leaves can also signal a phosphorus shortage. Where on the plant they start tells you which nutrient is likely involved.
Can the wrong pH cause a nutrient deficiency?
Yes, and in hydroponics it is the most common cause. An out-of-range pH stops roots taking up nutrients that are present in the water. Penn State lists high pH as the main cause of iron deficiency and a cause of magnesium deficiency, and low pH as a cause of calcium deficiency.
What causes tipburn in hydroponic lettuce?
Tipburn is calcium deficiency in the newest leaves. It is linked to pH and nutrient balance but also to airflow and humidity, because calcium travels with the water the leaf draws up. Keep the pH in range and run a gentle fan so the air around the plants keeps moving.
Why are my hydroponic plant’s leaves turning purple?
Dark green or reddish-purple older leaves, sometimes with burnt-looking tips, are the classic phosphorus deficiency picture. In hydroponics, check the pH first, since it strongly affects phosphorus uptake, then make sure the nutrient is mixed at full strength. Some basil and lettuce varieties are naturally purple, so compare with a healthy plant.
Can too much nutrient look like a deficiency?
Yes. Excess salts cause wilting despite plenty of water, dark green leaves and burned leaf edges, which can be mistaken for a potassium or calcium shortage. If the EC reads high, lower it with fresh water or a fresh, weaker batch before adding anything.
Will leaves recover after fixing a deficiency?
Usually not fully. Leaves that are already yellow or burnt rarely turn green again, so judge the fix on the new growth that appears over the following week or two. Healthy new leaves mean the problem is solved, and you can pinch off damaged old leaves if they look untidy.
Should I add a supplement for a nutrient deficiency?
Only after the pH, EC, roots and solution age check out. Most deficiencies in hydroponics come from those, not from a missing nutrient. If everything is right and the pattern still points to one nutrient, use a targeted product such as Cal-Mag for soft water or Epsom salt for magnesium.
