How to Read Your Plants and Reduce Problems in your Hydroponic Garden

Do you understand what your plants are trying to tell you?

Just like a newborn baby cries for what he/she needs — a plant will exhibit signs of distress, but they do so silently, communicating with visual cues, such as altered leaf colors and shapes.

Just like a new parent, if you learn to read these signs, you’ll be able to catch minor issues before they become big problems, thereby maximizing the productivity of your garden.

So here’s a lesson in plant language 101.

Quick Reference Guide to Secret Plant Signs

If you notice a problem in your garden use the following chart to help determine what your plants need.

Tower Garden Tip: Nutrient deficiencies, plant diseases, and other common growing problems can occur at the same time and look similar, so identification may be tricky. If you need help, take a sample of the affected leaf to your local cooperative extension office. If you live in the state of Georgia, here is a quick link:

(View a larger version)

by Logan Nickleson

Want to learn more about what your plants are trying to tell you? Let’s dive a little deeper…

Yellow Leaves and Nutrient Deficiencies

“Why are my plant’s leaves yellow?”

If you’re like most gardeners, you’ve faced this befuddling question before. Leaf yellowing — known as “chlorosis” in the world of science — has many potential causes. But one of the most common is undernourishment.

For healthy development, plants require 16 different micronutrients and macronutrients. And if they don’t get them or if proportions are imbalanced, leaves may start to look strange, become more susceptible to disease, and slow (or even stop) their growth — decreasing yields.

Symptoms of Plant Nutrient Deficiencies

Before you can address a deficiency, you’ve got to be able to figure out which nutrient your plant needs. So here are a few ways a plant may show you it’s missing something important:

  • Boron – Young leaves turn light green and may be disfigured.
  • Calcium – Leaves are disfigured and may wilt or show signs of necrosis (i.e., death of plant tissue).
  • Copper – Leaves may be limp and/or curled.
  • Iron – New leaves turn a pale, yellow color between green leaf veins (this is known as interveinal chlorosis).
  • Magnesium – Leaves show spotting and yellowing between green leaf veins. Outer edges of leaves may pucker or curl.
  • Manganese – Younger leaves turn yellow between veins (giving them a net-like look) and may develop dead spots.
  • Molybdenum – Older leaves yellow. Remaining leaves turn light green. All leaves may become distorted and narrow.
  • Nitrogen – Older leaves and veins turn a pale, yellow color. Other leaves turn light green and stay smaller than normal.
  • Phosphorus – Leaves looks stunted and turn dark green or even a deep purple color (almost black for some plants). Leaf tips may look burnt.
  • Potassium – Older, lower leaves show marginal necrosis, even looking scorched around the edges. Leaves also yellow on edges and between veins.
  • Sulfur – New leaves yellow and leaf veins lighten while older leaves remain green. (May be confused for a nitrogen deficiency.)
  • Zinc – New leaves yellow and may develop necrosis between veins.

For further help with identification, check out this visual representation of deficiency symptoms.

How to Fix Nutrient Deficiencies

The best way to solve deficiencies is to avoid them in the first place by giving your plants the nutrients they need.

For soil-based gardeners, that means using fertilizers, rich compost, and other amendments. But if you’re growing with Tower Garden, all you really need is Mineral Blend — a simple, balanced mix of all the key nutrients.

Tower Tip: Even if you’re providing the essentials, a high or low pH may keep plants from absorbing or processing them. Most plants access nutrients best when pH is around 6.5. So measure your levels every few weeks and adjust as necessary.

Other Causes of Discoloration and Disfigurement

Nutrition isn’t the only reason a plant’s leaves may look unusual. Here are a few other common causes.

Pests and Plant Diseases

It’s wise to watch for garden pests. Because bad bugs not only damage and stress plants — they also often introduce the following types of plant diseases, which bring additional harm:

  • Bacteria – Bacterial diseases can cause wilting and spotting.
  • Fungi – Some leaf fungi mimic certain symptoms of nutrient deficiencies, including yellowing and necrosis.
  • Virus – If you see blotchy or patchy yellowing on your leaves, a virus may be the responsible (especially if the discoloration is accompanied by disfigured growth).

Learn how to prevent and control these diseases »

Over (or Under) Watering

One of the most common, non-nutrient-related causes of yellow leaves is over or under watering. It’s a common cause, that is, for soil-grown plants.

Since Tower Garden automates the watering cycle, plants always receive the optimal amount of water. But if you’re growing in soil, here are a couple of ways to determine whether you should adjust your watering schedule:

  • Check the soil. (I know — it’s basic. But it’s never a bad idea.) If it’s drenched, it may be waterlogged, robbing plant roots of the oxygen they need to survive. In this case, water less.
  • Look for dropped leaves. Plants that don’t receive enough water drop leaves to prevent transpiration (i.e., the evaporation of water from plant leaves). So if you see leaves on the ground, water more.

Environmental Factors

Your growing environment can impact how your plants grow. Here are a few elements to consider.

When accompanied by thin, reaching stems, pale leaves usually suggest a plant isn’t receiving enough light. (Most plants need at least six hours of direct sun or, if growing indoors, 14 hours under grow lights.)

On the other hand, newly transplanted crops may develop bleached spots on their leaves after too much sun exposure. To avoid this, harden seedlings by gradually introducing them to the outdoors over the course of a few weeks.

Similarly, when growing inside, leaves that get too close to grow lights may become spotted or scorched due to over-transpiration, which is followed by yellowing, spotting, and, eventually, leaf death. The solution? Harvest more often!

To prevent wilting in a Tower Garden full of small seedlings (e.g., plants that are three inches tall or shorter), it’s best to use a half-strength nutrient solution: 10mL of Mineral Blend A + 10mL of Mineral Blend B per gallon of water.

You can safely increase nutrients to the full amount once seedlings have grown taller than three inches and developed a robust root structure. This usually takes less than a month.

Note: Even for mature plants, overly concentrated nutrients can also cause fertilizer burn. So make sure you’re always feeding your plants the proper amount.

Extreme heat often causes plants to wilt. But they usually bounce back once temperatures cool. That being said, these precautions can help protect your plants from hot weather.

If you notice black spots on leaves or plants after a cold snap, frost damage is likely the cause. Some plants — particularly kale, collards, and other hardy greens — can survive light frosts. More sensitive crops, such as tomatoes and peppers, however, usually die after freezing weather.

If leaves look dry around the edges and/or curl upward, they may be suffering from windburn. Consider setting up a wind barrier to protect them.

It’s completely normal for older, more mature leaves of a plant to yellow and die over time (as long as new, green leaves are replacing them). Just remove these old timers as you see them to prevent leaf fungi.

Start with good Seed (DNA)

One area that many growers overlook is starting with good seed stock. If you are growing seed from parent-plants that are soil-based, your plant will have to go through adapting to a new growing environment in hydroponics / aeroponics. Some of what your plant may be going through is simply poor genetics.

According to epigenetic experts, plants can store 5+ years of adaptation information in it’s DNA and call upon that information to deal with whatever it may be facing in it’s environment. If the plant was grown in soil in a totally different environment (i.e. you live where it’s hot, but the parent plant grew in a cool wet climate) that plant that you grew from seed may struggle to adapt.

Ideally, you want to start seed that has 1) grown in the same kind of environment you plant to grow in (ie: If growing hydroponically, you want to select hydroponic-adapted seed), 2) grown locally, and 3) grown organically (no chemicals applied to the parent-plant as it grew. It is okay if the parent-plant experienced stressors such as pest pressure or overcame disease as these stressors are encoded into the seeds. That means, if you collect seeds from your plants grown season-after-season, you will have stronger, more resilient plants because it has adapted to the environment you are providing.

So, if you are not wanting to collect your own seed, always try to purchase plants from a local grower that uses organic practices and collects their own seed. Grow Your Health Gardening Seed Company is one example and is especially good for anyone growing in the Southeast or in zones similar or near Zone 7. (Mentioning zones not for the sake of perennials, but to know similar growing conditions and weather patterns.)

Can you grow hydroponic-adapted seed in soil? Yes. Just know that plant may react differently depending on what is recorded in it’s DNA from parent-plants adapting and you may not have as a robust harvest if you had simply started with seed that was already adapted to your intended growing conditions.

What Are Your Plants Saying?

Now that you know how to decode your garden’s secret language, diagnosing and rectifying problems should be a little more straightforward.

Have any questions or tips of your own? Let’s continue the conversation in the comments below.

Want to learn more about growing your own food in a Tower Garden? Click here!

5 thoughts on “How to Read Your Plants and Reduce Problems in your Hydroponic Garden”

  1. I have grown several batches of lettuce in rock wool and have good germination but once the cotyledons emerge the lettuce plant continues to slowly grow its stem longer without producing anymore leaves until it eventually falls over and dies days later but the cotyledons and long stem are still green, what issues could this be? They are grown under 4 UV lights in pH adjusted water soaked rock wool cubes, any information you could lend would be greatly appreciated, thanks.

    1. Brad, It sounds to me like your light source is too far away if the stem is elongating. I recommend keeping light low (approximately 10-12″ away from the seedlings. As they grow, you can use a pulley to raise your light like this: Also, if you give your greens some blue or red light in the mix with white, it will also make for a stronger seedling. You can read up on the effects of lighting here if you’d like It’s also important the distance from the plant. Each LED has a “sweet spot” so be sure to refer to the manufacturer of your LED light and model to determine proper distance.

      Also, be sure you’re not letting your Rockwool sit in water. You want to water your young seedlings, but drain off any excess water and check moisture daily. When your seedlings begin to get a fingernail width tall, you may want to add liquid kelp (like this ) to water (see instructions on bottle for ratio – it’s a capful or tsp for a pitcher full is what I do) when watering young seedlings. This will give them a little bit of nitrogen without burning the leaves. Remember, you want your Rockwool to be moist to the touch, but now soaking wet sitting in water.

      Hope that helps! Let us know if these adjustments in your seed starting efforts work out better.—Erin

Leave a Reply