FREE SHIPPING on all orders over $100.

Diagnosing Plant Problems

No matter how much time and care you put into keeping your plants healthy and keeping your grow room clean, it’s always good to know the basics of diagnosing plant problems. If you catch your plant problems early and figure out what’s causing them, you can save your plants from any serious harm.

One of the trickiest things about coming to an accurate plant problem diagnosis is that a number of different factors can cause these issues, including pathogens, insect pests, and problems with the lighting or air circulation.

To help you understand the basics of diagnosing plant problems, we’re going to break problems down by category and briefly cover some of the most common issues.

The more you know, the better you can grow!

Use Your Observational Skills

Before we dive into some common plant problems, let’s cover some helpful information involved with diagnosing.

When you notice a problem, try to observe and jot down as many details as possible. When did you first notice the problem? Is it affecting all of your plants or just a few? What plant parts are affected?

For example, don’t just say that your leaves are discolored. Rather, say that the older leaves of all of your plants have a purple discoloration.

Along with taking detailed notes about the actual symptoms, it’s important to know the history of how you care for your plant. For example, if you have been feeding your plants with the fertilizer you happen to have laying around, you might be dealing with a nutrient problem.

Since some plant problems exhibit similar symptoms, it’s crucial you consider how you care for your plants. With that said, let’s explore some common types of plant problems.

Nutrient Problems

You probably know by now that plants need nutrients. However, it’s sometimes tough to figure out the correct nutrients to add to different plants during their various stages of growth. After all, plants require different nutrient ratios at different times. If you’re not using a nutrient feeding chart, it’s hard to know that you’re applying the correct amount of nutrients.

Therefore, it’s not uncommon to see the signs of nutrient deficiencies. But that’s not all! Too many nutrients can also cause plant problems. And what’s even more confusing is that nutrient deficiencies and toxicities can look similar.

Confusing, right? Sure, but you can still learn the basics of diagnosing nutrient problems.

Nutrient Deficiencies

Signs of nutrient deficiencies can be broken down into five main categories.

  1. Stunted growth of the whole plant
  2. Yellowing leaves
  3. Yellowing leaves in between the veins
  4. Purple/red color
  5. Dying plant tissue

If your plant has any of these symptoms, you should further explore the possibility of nutrient deficiency. However, it’s not as simple as saying that your plant is lacking nutrients; you need to find out which ones it needs!

To help you understand what nutrient your plant is deficient in, it’s good to understand mobile vs. immobile nutrients. Mobile nutrients can move throughout a plant, so deficiency symptoms first appear in older leaves. Immobile nutrients cannot move within the plant, so signs of deficiency begin in new growth.

Another factor to observe is whether discoloring is only present between the veins of leaves, only present in the veins, or present in the whole leaf.

diagnosing plant problems
Notice how the veins of the leaves are still green.

If you’re not sure what nutrient your plant is lacking (if any) you can send a plant tissue sample into a lab. While it may be too late to reverse the problem by the time you notice a decline in plant health and receive the test results, you’ll be better equipped to properly feed future plants.

Nutrient Toxicities

Just as plant growth can slow due to insufficient nutrients, plants can also suffer due to too many nutrients. Too much of one nutrient can lead to deficiencies in other nutrients. For example, if you have excessive phosphorous, your plants might suffer from zinc deficiencies. Remember, it’s important to balance nutrients!

Another type of problem to look out for is the presence of heavy metals. Cadmium, arsenic, lead, cobalt, and other elements can harm plant growth and health. Heavy metals can inhibit many plant processes including photosynthesis and therefore halt plant growth and lead to death.

Pathogen Problems

Oh, pathogens. Why do they have to exist? No matter if it’s a fungus, virus, or bacterium, pathogens can wreak some serious havoc on plants.

Fortunately, the symptoms of many plant diseases are relatively easy to diagnose — as long as you’re paying close attention to your plants.

Pathogen problems can be broken down into fungal problems, viral problems, and bacterial problems.

While these problems all vary in their symptoms and treatment, proper sanitation practices and a clean grow room are key to preventing these diseases. And if you don’t know what problem you’re dealing with, you can always submit a tissue sample to a lab that specializes in plant disease diagnosis.

Fungal Problems

Fungi cause some of the most common (and serious) problems in plants. Chances are you’ve seen some fungal plant disease in the presence of rotting roots or lesions on leaves. While fungi vary in their symptoms, most thrive in the same type of environment.

If you have a damp environment with poor airflow, fungal diseases are likely to appear. Some of the most common fungal pathogens include powdery mildew, downy mildew, anthracnose, and root rot.

Symptoms of fungal pathogens include the following:

  • Lesions on stems, leaves, or fruit
  • Damping-off of seedlings
  • Soft and/or rotten roots
  • Browning and death of plant tissue
  • Sudden and severe wilting of leaves
  • Powdery substance on plant tissue
  • Dramatic curling of leaves

So, if you notice any of these symptoms in your plants, it’s likely that a fungus is to blame. This is especially true if you have high humidity or low airflow where your plants are growing.

Viral Problems

Viruses are small, but they can cause some serious damage to plants. The symptoms of viruses vary quite a bit between each individual virus, so it’s important that you know the symptoms of each virus that may impact your plants.

An important thing to note is that viruses are not free-living. Rather, they live and reproduce inside of other cells. Therefore, plants must suffer a wound for a virus to enter and attack the plant. This wound can be caused by natural processes like the branching of roots. Or it can be caused by damage by humans (like pruning) or insects.

Pest Problems

No matter how much you wish you were the only one interested in your plants, pests will still attack your plants. If you’re growing indoors, you won’t have to worry about larger pests like deer, birds, and gophers. Instead, your main nemesis will be insects.

Before we dive into the damage that insect pests can cause, it’s important to note that insect pests can transit diseases. So if you see the signs of viral or bacterial problems, it’s also a good idea to look for insect pests.

Sometimes, you can see the pests themselves and know that you are dealing with a pest problem. However, sometimes the pests are hard to spot, so you might see symptoms of plant problems before you see the actual pets.

Here are some common symptoms that indicate you might be dealing with a pest problem.

  • Holes in leaves – both small and large holes
  • Small discolored dots on plant tissue know as “stippling”
  • Curling leaves
  • General plant weakness

Insect pests can be broken down into two main types: chewing and sucking pests. Both types can cause serious damage, but the way they attack differs.

Chewing insects make themselves known by eating plant tissue. So if you see holes in your plant leaves or chewed stems, you’re dealing with a chewing insect. Remember that not all insects will leave large holes. Even if you see small holes on your plant’s leaves, it’s a good idea to look around for insects. Some common types of these pests include caterpillars, beetles, and grasshoppers.

Sucking insects use straw-like mouthparts to suck the sap out of plant tissues. Not only do these insects suck the life out of the plant, but they can also introduce disease. Signs that you’re dealing with sucking insects include spotted tissue, wilting leaves, and the presence of a sticky substance known as honeydew. Some sucking insects include aphids, thrips, leafhoppers, and stinkbugs.

Lighting Problems

We all know that light is crucial to plants. After all, they need it to make their food! While there is a lot of debate about the best type of lighting, one thing is for sure: if you don’t provide adequate light your plants will suffer.

When diagnosing plant problems, it’s important to look for symptoms of both not enough light and too much light. Remember that plants don’t only need a certain number of hours of light, but also the proper intensity and quality.

If plants aren’t getting enough light you might see one or more of the following symptoms:

  • Dull, yellowing plants
  • Elongated and thin stems that look like they’re reaching for the light
  • Longer internodes (the spaces between where leaves grow out from the stem)

If your plants are getting too much light, it’s possible you’ll see the following:

  • Scorched/burnt leaves
  • Brown leaf tips due to excessive nutrient uptake

If you see symptoms that match those of too much or too little light, examine your lighting setup. It’s important to look at factors including the height of your lights, the intensity, and the uniformity.

It’s important to choose light bulbs that provide an adequate amount of photosynthetic active radiation (PAR) — the spectrum of light that plants need for photosynthesis. You’ll also want to check the intensity of the light, to make sure that you’re using a good bulb.

If you know your lighting system is set up to provide your plants with the right quality, quantity, and uniformity of light, your plants’ problems might have another cause.

Atmospheric Problems

The final cause of plant issues is an improper atmosphere. You probably know that providing an excellent grow room climate involves a lot of factors! You have to pay attention to the temperature, humidity, carbon dioxide, airflow, vapor pressure deficit, and more.

Therefore, if any of these factors are out of the ideal range, you might notice problems with your plants.

Since atmospheric factors can vary between days and months, it’s good to have an easy way to monitor them, like the Maxi Controller with data logger. You can customize the number of sensors to the size of your grown room, allowing for accurate readings.


If the temperature in your grow room is too low, your plants may exhibit stunted growth. Plants located in a room that is too cold may be slower to form leaves and flowers, and they might not flower at all.

If the temperature is too high your plants might show signs of heat stress. If you see drooping leaves or poor pollination, it’s a good idea to investigate whether or not your temperature is too high.

Remember that lighting plays a big role in grow room temperature. Both the type of light you use and the height of the lights impact how hot it is near your plants.


The humidity in your grow room largely impacts your plants’ susceptibility to disease and also impacts water and nutrient uptake.

If your noticing mold on your plants, this is a sign that your humidity may be to high. The problem itself is the fungal pathogen, but the cause may be high humidity.

The lower your humidity is, the more your plants will transpire. Therefore, your plants will take up more nutrients. So, if you notice signs of nutrient burn, it’s a good idea to check the humidity.

It is important to note that the ideal humidity level is related to temperature.

Carbon Dioxide

If you notice that your plants aren’t producing the yields you think they should be, they might not be receiving enough carbon dioxide. While a lack of carbon dioxide doesn’t always result in extreme symptoms, increasing the amount of CO2 can lead to noticeably higher yields.

You’re Ready to Start Diagnosing Plant Problems

Now that you know some common causes of plant issues, you’re ready to get started diagnosing plant problems. Remember, this is just a brief overview, and diagnosing plant issues will likely require further research. However, you now know the general causes of plant issues.

When you’re diagnosing plant problems, remember to take notice of even the smallest details. Frequent and careful observation will help you catch problems early and fix them before they get out of control.

So don’t be afraid if you see your plants looking less than ideal. You can figure out what’s wrong with them and get them back on the path to great health and big yields.


Fungal Plant Pathogens and Symptomology

Heavy Metal Toxicity in Plants

How Much Light do Houseplants Need?

Plant Nutrient Functions and Deficiency and Toxicity Problems

Temperature Extremes: Effect on Plant Growth and Development

By Briana Yablonski

Briana grew up in Eastern Pennsylvania and currently resides in Knoxville, Tennessee. She holds a Bachelor of Science in plant sciences from Penn State University and has worked on produce farms in Minnesota, Pennsylvania, Virginia, and Tennessee. She now runs her own small farm and enjoys walking dogs at the local shelter, hiking, and riding her bike.