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Troubleshooting Plant Issues: Top 14  Lettuce and Leafy Greens Problems and Solutions

Dying Tomato Plants

Beginners to hydroponics will typically want to start with easier-to-grow plants like lettuce or other leafy greens. These plants are not without issues, though, so we want to provide an all-inclusive guide to troubleshooting plant issues for your greens. Use this as an overview to get an idea of what you might face before you begin and come back later to pinpoint your issue. 

 

Troubleshooting Plant Issues in Your Nutrient System

In the wild, plants get the elements that build up their bodies from the air and soil. The air primarily provides Carbon while the soil provides a ton of nutrients that keeps growing plants healthy.

 

Plants grown hydroponically don’t have the ability to (literally) root out their own food from the soil. They’re completely reliant on you to provide it for them. As a result, problems in the nutrient delivery system can be devastating to your system and your plants. These are the most common we expect you will encounter:

 

  • pH Imbalances: Keep your nutrient solution pH between 5.6 – 6.2.  Throughout the day, crops pull in acids, out of the nutrient water, up through their roots, making your nutrient mixture more basic and raising your pH as time progresses. This is more normal than a pH drop. if your pH is dropping, check your EC level, if they are rising you may have to much nutrient in your water for the plants to absorb. dump some nutrient water and dilute the solution with some fresh filtered water. Check pH aggressively during the first few weeks using a reusable pH meter) to get a feel for the rate of pH change. Never correct pH problems too rapidly; add pH up or down to your reservoir slowly to adjust to your desired pH; This will avoid ‘shocking’ your plants.
  • Nutrition Levels: Thanks to iceberg lettuce, we don’t always think of lettuce as being filled with nutrients, there is a real need to continually be on top of nutrients throughout your hydroponic greens journey. Troubleshooting plant issues involving nutrients involves regular flushing and changing of water as well as selecting the correct nutrient blend for the plants in question. Visual analysis (see below) of your leaves can tell you a lot about what nutrients they are either getting too much of or lacking.
  • Calcium and Magnesium Issues: Calcium and Magnesium (Cal-Mag) are a particular group of nutrients commonly packaged together. While they both do a lot, we can say that Calcium primarily helps support rigid cell walls and Magnesium’s biggest role is in supporting healthy chlorophyll. If you’re noticing any of the most common effects of cal-mag deficiency (brown leaf veins or yellow/white areas between plant leaves) consider cal-mag supplementation and be sure to check out our detailed cal-mag deficiency guide.
  • Water Level: Water problems come from a variety of sources, including absent-mindedness filling and leaks. Sometimes you just plain forget to water your plants – getting a self-watering system or an appropriately sized reservoir will do wonders helping you in this regard. Regularly checking for leaks and knowing the ins and outs of PVC installation will help you avoid losing excessive amounts of water. Draining your dehumidifier water back into the reservoir helps too. Recycle-reuse!
  • Algae: Most systems will have some sort of Algae growth, somewhere, complete elimination is nearly impossible. If you get algae growth in your reservoir, it will leech nutrients intended for your plants as well as clog up the tubing. Avoid algae by preventing light from reaching all nutrient water sources. Use opaque reservoirs, trays, and pipes, even a bit of translucence will allow enough light through for algae to start propagating. Another common problem is having openings in your reservoir top (This is common in raft-type DWC and Ebb and Flow systems). Plug them all up with plumbers putty or caulk as best as possible. One method for this is to install an inline UVC light in your water filtration system. An alternative method used for algae blooms is to use an algaecide. Algaecides can help to control algae blooms, but if misused or overused, they can damage your plant’s root system. Humic acid and Grapefruit seed extract can also be used to prevent algae growth. Humic Acid“darkens” water, creating shade in deeper tanks and prevents light from entering and making algae blooms. Grapefruit Seed Extract is a natural solution that has been used in ponds and drinking water for years. Make sure you remove the dead algae from the system as your remediation efforts begin to overtake the algae or the dead algae will rot causing even more problems. 
  • Water Temperature:  Another common water problem you’re likely to face when troubleshooting plant issues is using water that is too hot or too cold. On average, tap water comes out at 55 F (12.8 C) but can plunge down to 45 F (7.2 C) during the winter. Running it through a filter does not help the temperature. How would you like to be forced to stand in cold water for an extended period of time after being nice and cozy warm? Your plants won’t like it either. These cold temperatures during water chang outs, shock and harm roots, and reduce water and nutrient intake. Let the water sit and warm up to room temperature in the reservoir before running through the system. Titanium tube water heaters work well here as well to maintain a comfortable temperature. Don’t let the water temperature get over 65-70 degrees as this will allow for bad bacteria, and fungi to proliferate! Outside and summertime installations may require a water chiller. 
  • Cleanliness: Sometimes troubleshooting plant issues comes down to good old-fashioned cleaning. Dead plant matter, which includes roots and leaves, is also a hotbed for plant-killing, nutrient sapping bacteria, and fungi. Give your roots regular checkups when changing nutrients and prune away older, senescing leaves judiciously.

 

Troubleshooting Plant Issues Related to Lighting

As consumers of light, plants need both high quality and high quantities of light to match the power of the sun. Completely indoor systems placed in dark corners of the home need to be especially wary.

 

Remember that troubleshooting plant issues related to lights go beyond your wiring and the electrical grid. Buying the right LEDs for your system is essential.

 

  • Lighting Distance: When going about troubleshooting plant issues related to lighting, this is the easiest one to start with. When using purely artificial light, experts recommend having a gap from bulb to top of the plant of about 6 to 12 inches for hydroponic lettuce and greens. For seedings, you can adjust this closer to 4 to 6 inches. If your lighting is too close your crops will suffer from leaf burn, while lighting situated too far away will create tiny, shrimp plants.
  • Light Timer Settings: It is so tempting to leave your lights on all day so plants can grow full time. But, much like humans, they need to rest during part of the day and recharge. These “tired” overlit plants will grow in a stunted manner with misshapen leaves. While lettuce is good at around 14-16 hours of light, spinach will bolt and seed if exposed to more than 14 hours of light – one of the most underdiagnosed problems with spinach.

 

 

Troubleshooting Plant Issues Related to Climate Conditions

The climate (of your room or greenhouse, not the Earth!) will also play a big role in the proper maintenance of your plants. Holes or openings can allow in bugs, alter temperatures, and mess with your humidity.

 

Troubleshooting plant issues of this type require you to view the structural integrity of your entire project, but the solutions to your problems aren’t necessarily so difficult.

 

  • Bugs: Insects and mites will be frequent visitors to your hydroponics gardens, and they’ll stay awhile if you let them. If you start seeing small holes in your leaves or strange, silky webbing on the outside of them, look around for bugs. Using a magnifying glass (many pests are under a millimeter long) examine the tops and undersides of the leaves of your plants. Many bugs like to congregate around juicy, nutrient-rich veins. Apply pesticides or use biotic controls, like ladybugs or predatory mites, to control these pests.
  • Room Temperature: Controlling room temperature to please everyone can be difficult just amongst humans, but our plant friends need the same sort of attention to detail. Temperatures that are too high can stress out plants to the point where they are bolting – growing rapidly to produce seeds before death. On the other hand, temperatures that are too conservative cut into yields. A research project coming from Purdue University observed triple yields from butterhead lettuce grown at 65-70 degrees F vs 55-60 degrees F.
  • Room Humidity: Rooms with high humidity can cause a wide range of problems, among them, being the spread of fungus and powdery mildew or preventing some crops from flowering. While proper ventilation (see below) certainly helps, the cheapest and most reliable methods to reduce humidity all come from “cultural practices” within your greenhouse space. Keep water off your floors and other surfaces, such as bucket tops, that will later evaporate. Even leaky faucets and hoses can contribute heavily to this problem. Keep Relative humidity (RH) in your grow area between 50-60%. your humidity level is over 70% your plants will have a difficult time releasing water through their stoma. Stoma or stomas (pl), are the microscopic openings or pores in the epidermis of leaves and young stems. Stomata are generally more numerous on the underside of leaves. They provide for the exchange of gases between the outside air and the branched system of interconnecting air canals within the leaf. This will cause them to stop drinking up water (which has all the nutrients) and will cause the tips of the leaves to dry out and turn brown.

 

 

Troubleshooting Plant Issues Related to Ventilation

Proper ventilation helps your plants get the proper gas exchange they need and deters disease, excess humidity, and unpleasant smells. Proper planning goes a long way towards preventing these problems before they occur and, if you’re using a grow tent, getting an amazing ventilation fan will be a natural first step.

 

  • Overcrowding: In traditional agriculture, thinning your plants is vital to give your plants the space they need to grow big roots, large leaves, and bountiful veggies. Hydroponics isn’t so different. It can be very tempting to put two plants into one slot on your build (2-for-1 yay!) but the reality is you are not doing them, or you, a favor. Paring down your plants to one healthy individual per slot, even if a bit spacious, will pay off come harvest time and promote healthy airflow throughout your build.
  • Adequate Airflow: When troubleshooting plant issues like tip burn, never forget the importance of adequate airflow within your system. Fresh, moving air keeps leaves busy and prompts roots to drink up your nutrient water mix. Stale air promotes less activity, leading to tip burn from low Calcium levels. Stagnant and stale air also provides a breeding ground for mold and fungus.

 

Visual Diagnostics for Troubleshooting Plant Issues

If you find yourself unsure as to what issue you’re facing, but can clearly see a problem, then you’re in the right place. Cross-reference our pictures and descriptions below with what you’re seeing in your greenhouse. Then, check out our chart to get the whole story.

 

 

Visual Guide to Leaf and Root Problems

While leaves on trees change colors in the fall to signify that they are readying themselves for winter, radical leaf color changes in your hydroponic crops can signify something far more sinister. Changes in size and shape may also occur. When troubleshooting plant issues related to leaves and plants, careful observation is key! 

Lettuce Tip Burn on young leaves
Lettuce Tip Burn on young leaves

Tip burn, younger leaves: The edges of your newer growth leaves are browning. The causes can be many different issues, nutrients, pH, but is usually environmental.

  • Boron deficiency- less likely
  • Calcium deficiency – Common. Algae can also potentially leach the Calcium from your reservoir tank.    
  • Airflow  – More likely. Is the airflow too Hot, moving too much air, or moving too fast – Common
  • Calcium deficiency – Common. Algae can also potentially leach the Calcium from your reservoir tank. 
  • High soluble salts – Common. If you are not regularly adding water and nutrients then you should flush your reservoir and add new filtered water and nutrients. This will cure almost all issues.
  • Humidity – Very Common. Most likely your humidity is too high and your plants are not transpiring which can cause deficiencies in water and nutrient uptake. Also common for fruiting plants that will not flower.

 

 

Lettuce Tip Burn on older leaves
Lettuce Tip Burn on older leaves

Tip burn, older leaves: The edges of your plant’s older leaves are browning, possibly with spots and dark brown veins.

  • Zinc – Very unlikely if  plants are feeding and you regularly add Nutrient to maintain the EC level 
  • Nitrogen deficiency – Less likely if plants are feeding and you regularly add Nutrient to maintain the EC level 
  • Calcium deficiency – Common. Algae can also potentially leach the Calcium from your reservoir tank. 
  • High soluble salts – Common. If you are not regularly adding water and nutrients then you should flush your reservoir and add new filtered water and nutrients. This will cure almost all issues.
  • Humidity – Very Common. Most likely your humidity is too high and your plants are not transpiring which can cause deficiencies in water and nutrient uptake. Also common for fruiting plants that will not flower.

 

 

Dying or Yellow Older Leaves: Your older leaves are senescing or dying. For many plants, this is a natural part of the life cycle, but if you notice it happening too early it could be a sign of Magnesium deficiency, which becomes symptomatic in older leaves first.

Dying or Yellow Newer Leaves: Quite a bit more distressing than the above situation. Can be caused by multiple sources – over or under watering, too much shade, or nutrient deficiencies (especially Calcium).

 

Leaves curl In or down
Leaves curl In or down

Leaves Curl In or Down: This can be caused by a variety of problems; nutritional deficiencies (Copper and/or Potassium, among others), overwatering, or underwatering. That’s right, both too much water and too little water can cause this issue!

 

 

Leaves curl Out or Up
Leaves curl Out or Up

Leaves Curl Out or Up: Dark green leaves that curl downward are a clear sign of nutrient overload – the plant does not have time to process the full load and droops as a result. Other ways that plants can be affected by leaves curling down include pests, disease, and overwatering.

 

 

Yellowing between veins
Yellowing between veins

Leaves Changing (Other Colors): Nutritional deficiencies such as Nitrogen, Zinc, and Iron cause leaf yellowing, regardless of age. Phosphorous deficiency can lead to leaves developing purple spots. White leaves are the result of powdery mildew or overexposure to light.

Wilted Leaves: Over or under watering, Could also be that the temperature is too hot or the air is too dry.

Drooping leaves: Temperature is too hot or plants are not getting enough water.

Leaf Drop: Too cold, drastic temperature change, or too much water

Burnt patches on leaves: To close the grow lights

Root Burn, Black, and Rot: Root rot is caused by a lack of root oxygenation. Roots need to “breathe” and will die off if not able to. Fogponics systems and those that use moving water or proper aeration devices will avoid this problem.

 

 

 

Problem Appearance Possible Cause Solution
Tipburn Leaf browning along edges; either in spots or solid. Calcium deficiency either from low Calcium, poor or too much airflow, high humidity, or Algae in water. Lower Humidity, Provide Adequate Airflow, Algae clarifier, or Add Cal-Mag
Dying or Yellow Older Leaves Older leaves are dying, yellow, and/or senescing. Magnesium deficiency (or older leaves) Calcium and Magnesium Levels
Dying or Yellow Newer Leaves Younger leaves are dying or yellow. Over or under watering, too little light, or Calcium deficiency. Water Level, Light Timer Settings, or Calcium and Magnesium Levels
Leaves Curl In or Up Leaves curling in an upward and inward fashion. Copper or Potassium deficiency, overwatering or underwatering. Nutrition Levels or Water Level
Leaves Curl Out or Down Leaves curling in an outward and downward fashion. Nutrient overload, pests, disease, overwatering. Nutrition Levels, Bugs, or Water Level
Leaves Changing (Other Colors) Leaves changing to various, unexpected, colors. Yellow and Purple – Nutritional deficiency; White – Powdery mildew (area needs proper cleaning) or overexposure to sunlight. Nutrition Levels, Cleanliness, Lighting Distance, or Light Timer Settings

 

 

Common Diseases

If the pandemic has taught us anything, it is that diseases travel through communities quickly. Identifying fungal and bacterial conditions early and starting treatment immediately can make a huge difference in current and future yields. Check early and often for signs of the following icky slimy or fuzzy conditions.

 

  • Powdery Mildew: This common fungal disease has its name for a reason – it appears as a powdery spot growth on plants in a sort of ashy color. As the disease progresses, the leaves will begin to shrink and die. Use a fungicide on the area and prune affected leaves away upon sight.
  • Grey or white mold: Also known as Botrytis crown rot, grey mold targets the crown of your lettuce heads. It appears to be fuzzy and grey in color. Note that it grows easily on dead plant matter, giving you further reason to clean up dead and senescing leaves.
  • Webs: Spider Mites!
  • Shiny Trails or spots: Aphids
  • Green on growing medium: Algae
  • White Crystals on growing medium or around reservoir: Salt and mineral buildup. Clean, dump then flush system with clean water for 24 hours and dump again. Add new filtered water and nutrients and rebalance pH.

 

Common Hydroponic System Pests

If t you have a system in your home, shed, or basement the odds of getting these pests are less likely but it can still happen. These pests and easily get into your plant growing area via clothing and by not practicing good hygiene. Always wash before entering your plant area. Use rubber gloves and even masks when handling nutrients, chemicals, medium, and plants. If you really want to take it up a notch change your clothes or wear a lab coat while in the grow room or area.

 

  • Aphids: Clusters of tiny squishy insects on the underside of leaves.
  • Whiteflies: Tiny moths flying around.
  • Spider Mites: Visible webs. Tiny yellow or white speckles on leaves
  • Thrips: leaves will curl up or have white or silver spots
  • Fungus Gnats: Swarms of tiny clack flies hanging around the reservoir tank or on the medium

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Grammy

I'm Grammy to my grandkids and most of the authors here. My gardening career started when I was a child digging and planting in my neighbors garden in Florida. As a teenager I worked on one of the first organic farms and learned the many benefits of organic farming. As a young Mom I started dabbling in hydroponics and became hooked! My family and I learned from research and "Hard school of Knocks " ways to improve our crop growing techniques which I am willing to share with you.