How To Identify & Treat Plant Root Problems

How To Identify & Treat Plant Root Problems
January 21, 2020

A strong root system is (literally) the foundation of a healthy cannabis plant. Marijuana root problems need to be identified as soon as possible, though roots are easy to overlook and tricky to inspect. Fortunately, your plant will let you know of any root issues with tell-tale signs on the leaves. Once you’ve learned to diagnose and resolve these issues, you’ll be more able to produce big yields of high-quality, homegrown cannabis.

This article will look at why roots are important to the overall health of the plant, with a tutorial explaining how to properly identify cannabis root problems. It will talk about the possible causes of these problems and show you the best ways to deal with them quickly, cleanly and organically.

The importance of healthy cannabis roots

A healthy root network is essential for good plant growth. Roots are not simple drinking straws, they have numerous responsibilities including stability, storage and circulation.

Healthy Roots Of Marijuana
  • Anchor. A robust, deep root system acts like an anchor that holds plants upright in the growing medium.
  • Nutrient Absorber.Roots absorb water and nutrients from the soil and deliver them to other parts of the plant.
  • Storage SystemRoots serve as storage systems for the critical carbohydrates used during the flowering stage. This is when stored starches are sent back up to sustain the growth of the plant.
  • Better Soil. Healthy roots actually improve the soil around them, increasing both organic activity and organic matter accumulation.

How to identify marijuana root problems

Observation is key. Learn the language of the plants.

 – Kyle Kushman

Depending on the medium used to grow your cannabis plants, it can be difficult to keep checking and rechecking the actual roots. The stress caused to the plant may end up being worse than the original problem! 

Luckily, the leaves and stems do a very good job of alerting growers to issues below the soil, so the real key to identifying marijuana root problems is observation.

Marijuana root problems: the signs

  • Curling or cupping of leaves.
  • Discolored leaves.
  • Burnt leaf edges.
  • Droopy, lifeless plant. 
  • Wilting of the stems.
  • Stunted growth.
  • Foul-smelling run-off.
  • Dead, falling leaves. 

How do I treat marijuana root problems?

Cannabis Root Problems

Time is of the essence when dealing with marijuana root problems. Plants are complex organisms and some of the symptoms above could indicate other issues such as nutrient deficiency or light burn. The key thing to understand is that things like nutrient deficiencies can often be traced back to the roots. For example, if your pH is off, the root’s absorption rate drops and your plant won’t get the nutes it needs – no matter how measured and accurate your doses are. 

With this caveat in mind, let’s take a look at some of the common causes and remedies of marijuana root problems.

Is temperature the cause of my marijuana root problems?

Roots are terrible at regulating their temperature, far worse than the stems and leaves. You can imagine how uncomfortable it can get being surrounded by black plastic inside a reflective tent with high pressure sodium lamps beating down on you. Makes you sweat just thinking about it. 

If the mean soil temperature is outside the optimum range (68 to 75 degrees F) your roots won’t function properly. They’ll become more susceptible to pathogens and your plant will grow sickly and weak. If you do suspect things are too hot (or too cold), stick a thermometer in the soil to find out.

How do I regulate the temperature of my cannabis grow?

Maintaining the optimum temperature range is VITAL to a successful grow. When things get too cold, life slows down. Too warm and life can speed up too much – fungus, mold, mildew, blight, pests – they love it wet and they love it warm. Keep control of your temperature and you’ll have solved half your problems before they arise.

Controlling temperature when growing weed indoors

Growing indoors in a controlled setup offers more flexibility in regards to variables like temperature. Keeping the growing space at room temperature will help the roots avoid stress. When using High-Intensity Discharge (HID) lights, be sure to set up a proper exhaust system to remove excess heat. If the problem is lack of heat, stronger lights can be used. The easiest (but not cheapest) thing to do is install air-conditioning and check the temperature regularly. And don’t forget fans! Your fans will mimic the wind and make your plants stronger, they will invigorate stale air and, when placed correctly, will keep the top layer of soil dry (discouraging problems with fungus gnats, for example).

Controlling temperature when growing weed outdoors

Outdoor cannabis grows aren’t as controllable as indoor grow rooms. Still, there are plenty of ways to maintain ideal temperatures for healthy root growth. Leaves, grass clippings and other organic matter can act as natural insulation for the soil. Covering the ground with mulch will also help keep the root zone cool in the summer and warm in the winter.

Cultivating the soil will also help maintain optimum temperature. Compared to compact soil, loose soil does not heat up or cool down too quickly. This reduces the risk of stressing the roots with abrupt temperature changes.

Is watering the cause of my marijuana root problems?

Watering Marijuana Plant

Just like pretty much every living thing on Earth, plants need water to survive. But how often do you water a cannabis plant? How much do you water cannabis? How do you know when it’s time to water again?

Put simply: don’t overwater the plant or the roots will drown; if you under-water, the roots will dry out. Both outcomes are the same: dead plants.

Only water the plants when needed. One way to check whether the soil needs watering is to poke your finger into the soil. If it’s dry deeper than an inch or two down, it needs a drink. For potted plants, try lifting the container to see if it feels light – this is an indication that it needs watering. These are just tips, if you want a real, in-depth look at how to water your plants properly, check out Kyle Kushman’s video on feeding and watering. Another simple thing to check is drainage. Holes should be drilled at the bottom of containers to prevent standing water.

Soil isn’t the only medium in town. It’s worth taking notes on other growing media, too.

  • Soilless Mixes. These mixes, comprising of a combination of peat moss, coir, vermiculite, perlite and many other materials, are easy to maintain. Soilless mixes drain well, reducing the risk of drowning the plant.
  • Compost. Aside from having high levels of nutrients, composts tend to retain just the right amount of water for a healthy cannabis plant.
  • Rockwool. Rockwool is a cool name and a cool material, it’s fiber made from melted rocks. It holds water so well that your only concern is over-watering.
  • Sand. Sandy mediums are naturally loose, making them a little too efficient at draining. Cannabis plants grown in this medium may need to be watered more often.

Are my pots the cause of my marijuana root problems?

Make sure you use the right size pot for your plant. Too big and the roots might struggle for oxygen, too small and they will become root-bound and suffocate. If your marijuana plant grows too big for the pot, consider transplanting it to a larger container.

A small 1-gallon pot is enough to start a seed, seedling or cutting. After 4 – 6 weeks, the plant can be moved into a bigger container. The size of the pot depends on what size you want the fully matured plant to be. This table is only a guide. Different strains show different characteristics so always check with your online cannabis seedbank, they’ll be happy to advise you further.

Recommended Pot Size for Cannabis Plants
Plant SizeContainer Size
12 inches2 to 3 gallons
24 inches3 to 5 gallons
36 inches6 to 8 gallons
48 inches8 to 10 gallons
60 inches12 gallons and above

Are my marijuana root problems from hydroponics?

When growing in a hydroponics setup, root problems are likely caused by a lack of oxygen in the water – often caused by algae buildup. Water temperature also plays a big part.

Hydroponics Set up

It’s almost impossible to fully control algae in hydroponic systems. Algae can be tolerable for the most part – provided the growth is not excessive. Regular scrubbing between crops helps to control it. Algaecide products can also be used, but we don’t recommended them – they can damage young roots and cause more issues than they resolve.

Temperature is another common issue in hydroponic setups. If the temperature of the water creeps above 75 degrees F, it loses the ability to hold oxygen and your roots will start to suffocate.

Does my marijuana plant have root rot?

When left untreated, root problems can develop into a condition called root rot. Dying roots start to decompose and attract things like fungus, pests and disease… leading to dead or dying plants. You might have fixed the cause of the initial root problems, but what can you do once root rot has set in? How do you get rid of root rot from a cannabis plant?

Can I use beneficial bacteria to kill root rot?

Beneficial bacteria help to break down organic matter and facilitate nutrient uptake. They can also add a layer of protection against harmful pathogens. Mycorrhizae and Trichoderma are especially beneficial. Generally, the larger the community of beneficial bacteria, the quicker it can destroy pathogenic microorganisms.

Beneficial bacteria can be introduced to the root zone in two ways.

  • Compost Teas.One way to promote the growth of beneficial bacteria is through the use of all-organic and inexpensive compost teas. The nutrient-rich, liquid fertilizer is made by brewing compost in water. It involves agitating steeped compost in aerated water for at least eight hours, before filtering the water from the solid residue. The resulting concoction can then be applied directly to the soil for the microbes to seep into the root zone.
  • Commercial Solutions.There are commercial solutions available that help create and maintain a healthy bacteria  population.Specialized microbe mixes such as Voodoo Juice and Tarantula are blended to enhance root zone health and the growth of cannabis plants. These solutions contain dormant microbes, activated by contact with water. They can either be applied directly to the soil or mixed into the nutrient solution of a hydro setup.

Should I use hydrogen peroxide to kill root rot?

Hydrogen Peroxide (H2O2) is often used as a quick fix to kill things like viruses, fungal spores and bacteria. As the H2O2 breaks down inside the nute solution, it starts firing off oxygen atoms that either oxidize organic molecules or pair up with other oxygen atoms to create a more stable molecule. This can be beneficial in two ways: the baddies die and the roots get more oxygen. 

There is a dark side to H2O2. Some gardeners worry about the indiscriminate way the oxygen atoms rampage through the soil, as they do not know the difference between beneficial organic molecules and harmful ones. It’s been described as chemo for plants – sure, some cancer cells will die, but a bunch of healthy cells die, too. You can also think of it like an aggressive antibiotic that will cure your chest infection while giving you a rancid bout of thrush.

While it might well be an effective treatment of marijuana root rot, it can also cause some serious harm to both the plant and the ecosystem around the plant. We would recommend further reading and lots of thought before you nail your colors to the H2O2 mast.

Keep your root zone healthy!

Maintaining a healthy root zone is the simplest way to head off marijuana root problems. Once your roots are in distress, it’s difficult to nurse them fully back to health. This is why you must repeat and repeat that old cliché: prevention is better than cure, prevention is better than cure. Think about temperature and humidity, look at the soil – is it nice and airy or thick and muddy? Is the plant outgrowing its pot? Is the pot draining properly? Are you really going out in that shirt?

Cannabis On A Bucket Containers

You have to hit the proper balance of hydration and aeration without being too proud to add beneficial microorganisms. They’re natural and organic and they shouldn’t break the bank. Check the plants regularly, TEND to them, look for signs of distress and react quickly to any problems you find. And don’t worry, if you’re on top of things in the tent you’ll be able to spot and solve 99% of ANY issues quickly and cleanly. We believe in you! You can do it!! And that shirt looks amazing!!!