Yellow Leaves - Causes and Fixes

When our plants leaves turn from green to yellow, it is an indication that something in their environment is not jiving with them. The sooner we catch the issue and correct it, the better your plants will fair. 

Causes of yellow leaves on hydroponic garden

Here are 6 causes for yellow leaves and how to fix them:

  • Cotelydons (the first two leaves that sprout) will eventually yellow and die off as the true leaves grow, this is a good and natural process.
  • Lack of Calcium Magnesium - can cause leaves to yellow. If you are adding the suggested amount of MagiCal to your nutrient feedings then this is likely not the cause. 
  • Overfeeding - Nutrient burn from using too much nutrients will show yellow to brown spots on the tips of leaves. Initially nutrient burn is on the tips of the leaves and has a crisp burnt look to it. The basil plant pictured below shows nutrient burn, brown tips on leaves. Read more about Nutrient BurnNutrient burn on tips of leaves from overfeeding
  • pH Imbalance - leaves can turn yellow if the pH in your nutrients is too high or too low. Ensure your reservoir is at least 80% empty before adding the next pahse of nutrients. When plants are young this can mean waiting 9-14 days, rather 5-7 days for mature plants, as they do not require as much water. This will ensure the nutrients has been used up, so you are not adding additional load to the system, which can alter your pH. Alternatively if you don't want to wait, at the end of a 1 week cycle turn off the pump and manually empty the reservoir and refill it with fresh nutirents. The organic nutrients provided will automatically balance the pH when added to 4 liters of fresh water. Make sure to measure out and pour each nutrient into fresh water individually, rather than mixing together and then adding to the water. Well water - can affect the pH of your nutirents due to containing mineral elements. We reccomend that you do not use well water for you indoor garden as it can cause build up on the pump. We reccomend either distilled water (not spring water), or purchase a filter that can filter out minerals, or invest in a water softener system. 
  • Pests - To keep your garden pest free you can watch the video below for helpful tips and what to do if you get pests in your indoor garden.
  • Root rot is a fungi that will turn white, healthy roots to dark brown and mushy. This prevents the plant from being able to absord nutrients and deficiencies becomes apparent in the condition of the plant's foliage. Leaves begin to wilt and turn yellow and growth slows. Root rot is most common in young plants. While it is a serious issue for plants, treating the problem as soon as the symptoms occur can save your plants. Beige roots are ok, as this is the organic nutrients dying them. The key indicator is what do your plants look like? Are they green and healthy, or yellow and disstressed? Pictured below is a net pot covered in white fungi and root rot. Now lets discuss causes and solutions.

     Root rot and mould on hydroponic plants and how to fix

    What Causes Root Rot?

    There are several factors that can lead to root rot:

    • Light getting into your roots. Roots need a dark environment. Fix: be sure to top up the net pots with the clay pellets once you are at the seedling stage. 
    • Lack of Oxygen - the pumping up and trickling down of water is an essential element in the design of the verde-Garden. This movement oxygenates the water to deliver oxygen rich water to your plant roots. Too much water; however, can make the roots soggy, creating the perfect environment for fungus to grow. 

    How much you need to water depends on three things: the type of plants you’re growing, the size of the plants, and the indoor environment. During the germination and seedling stage you want the coco coir to go from "wet" to "moist" but never to "dry." Waterlogged conditions prohibit roots from taking in the oxygen they need to survive. 

    Warm water holds less oxygen, which makes it more susceptible to root rot and mold. Air temperaures that are too cold (below 15 Celsius) can invite bacteria. Maintaining temperatures between 17-23 degrees Celsius is ideal growing conditions for indoor gardening.

    How to Fix Root Rot and Other Fungi

    Plants do not spontaneoulsy die, but if the conditions that have caused it go unchecked long enough then they will eventually sucumb to it. In other words, it can be fixed if caught in time and adjustments are made. 

    • Remove all plants and brush off mould with your hand, do this away from the garden and other plants. Leave the plants in their pots, and rinse the pot and clay pellets under the tap in cool water. 
    • Trim rotten roots off and wash off any slime or plant matter on the bottom of the pot with cold water. 
    • Remove the verde-Garden from the wall and follow the cleaning tips. Be sure to clean the pump and irrigation tubes with cold water. Flush the irrigation tube by running water through it under the tap. This ensures that any fungus in the indoor garden has been removed. 
    • Add 1/2 a tank of fresh water to the clean reservoir and resassemble your garden. 
    • Ensure the clay pellets cover the top of the pot so light is not getting into the roots. 

    Reduce the Watering Cycle

    If your plants are seedlings or young plants, reduce the watering cycle to 5 minutes ON and 4 hours OFF. Repeat this cycle 4x per day and leave the pump OFF for 12 hours at night. This will allow the coco coir pucks to be less saturated or "barely moist" and kill the wet environment the fungi requires to grow. Watch the plants for signs of wilting (an indication that they need more water).

    Check the base of the pots daily. Be careful not to crush any new white roots, but brush off any new mold and rinse with fresh water. Repeat as much as necessary. Once the seedling have new white roots (usually about 1 week), you can add the nutrients level you were using prior to the change, be sure to top up your reservoir. Pictured below after 3 days on reduced watering schedule, new white root with fuzzy white hairs, showing signs of good plant health. (It looks similar to the mould, but these are directly on the end of the roots, and is a sign of health). 

    Fine white root heair on healthy hydroponic plants    

    Increase Water Cycle

    Once your plants have recovered and have developed healthy new roots, increase the watering cycle to 3 hours ON and 4 hours OFF twice a day. You will need to gauge whether your plants are drying out in between cycles, wilting leaves is a great indicature, in which case you can adjust accordingly. Larger plants will require at least 8 hours ON/16 hours oFF of water a day to ensure the coco pucks do not dry out. 

    Root Rot in Mature Plants

    If your plants are mature when the root rot occurs, you can clip away the dead dark roots, leaving the white roots intact. Follow the fresh water rinse under the sink and clean your garden, as above. Run fresh water only (no nutrients) in your reservoir for 1 week. Reduce your watering schedule. If you are at 12 hours ON, reduce to 8 hours ON and observe for signs of recovery.

    Signs of Recovery

    • Yellow leaves dispate and/or new growth of healthy leaves
    • New growth of healthy white roots
    • No further development of rotten roots (once the bad ones have been trimmed away, you are not seeing more). 
    • Once nutrients is re-introduced into the system, plants begin to take on growth, a sign of healthy roots. 

    Ongoing Maintenance and Prevention

    Routinely check your plants from their leaves all the way down to their roots. 

    If your roots get big matts, regularly trim the bottom 1/3 your roots to allow oxygen and nutrients to flow more easily. 

    Run fresh water flushes in your reservoir about every 6-8 weeks, and clean the garden about every 10-12 weeks (after a harvest cycle). 

    If you have questions, feel free to Contact Us and we will help walk you through it.