When growing cannabis, problems can arise that are out of your control. It can happen to new, and experienced growers. What makes the difference is knowing how to treat these problems when they do arise. This article covers common cannabis plant problems and solutions.
Using the information here, you can quickly diagnose cannabis plant problems and find the right solution. The most important thing is not to rush into treatment, always make sure the diagnosis is right. You do not want to make the problem worse.
If you have any cannabis plant problems you need urgent help with, then feel free to ask for help in our cannabis growers forum
When growers see a ‘Nutrient Deficiency’ in a cannabis plant, it is mostly likely to be, a pH problem. If pH is too high or too low, your plants ability to uptake nutrients will be effected
Because the plant can not uptake nutrients properly, they appear to be deficient. But there are plenty of nutrients in the medium, but because of pH lock-out, the plant can’t eat them. Adding more nutrients may make the problem worse, by throwing the pH off even more. Also, it will further raise the EC, which can lead to nutrient excess.
If you suspect a nutrient deficiency, check and adjust the pH before adding more food to the medium. PH charts for hydroponics and soils are shown in the charts below. You can see that certain nutrients are not available, when the pH is not in check.
If the pH is fine, then increase the EC of your feed by 0.2 points, or add a supplement to increase whatever nutrient your plants need. For example, as cal mag, or a heavy PK booster or extra nitrogen.
Over watering your Cannabis plants
The symptoms of over watering a cannabis plant are, leaves wilting or drooping and yellowing of the plant. Also, if growing in soil, the medium may be smelly and soggy. This is because the roots are being restricted from air, and bad bacteria is breeding in the root zone.
Increase the temperature of the grow room, and direct more airflow towards the pots. This will evaporate some of the excess water. You should only water when your soil/medium is dry. Proper watering technique is important when growing in soil.
To avoid over watering again, wait for you pots to be light, and the top inch of your medium to be dry before watering again.
If your plants are showing symptoms of over watering in hydroponics systems, then there may be a problem with your airstone. Check for blockages and ensure a good supply of air is reaching the roots.
Over Feeding a Cannabis Plant
Most new growers will start growing cannabis and follow the dosage on the nutrients bottle. In most cases, this dose will usually be far too strong and will soon lead to excess nutrient issues. This makes over feeding a common cannabis plant problem.
Some nutrients used for growing cannabis, were designed for growing other fruits and vegetables. The cannabis plants doesn’t eat a lot. Always start off with 1/4 of recommended dosage, or 0.2 point over your background EC. Then, slowly bring up the dosage as the plant gets hungrier, and back off at any sign of excess.
Flush your medium to remove old foods and salts. Reduce the EC/ PPM of your next few feeds until the plants recovers. Follow what your plants eat by monitoring the EC of the run off. This is a reliable way of knowing what your plant is being fed, too much or not enough.
PH imbalances in the Medium
PH problems can show themselves in different ways. Anything from: nutrient deficiencies, to excess and nuit burn. The important thing is finding out the problem, and most of the time, knowing the pH can help.
Check and adjust the pH level as necessary. You can adjust the pH in hydro by using pH up, and pH down. Some of these liquids can be highly concentrated, and only a few drops will be needed to correct pH levels. To make adjustments easier, dilute 10ml, into 1L of water. Using this will make pH adjustments so much easier.
If you’re growing organically, you will not want to use these chemicals in your medium. To lower the pH in organics, use either lemon juice, or vinegar in your feed. To raise the pH, you can use baking soda. Treat your soil with dolomite lime before growing in it. This will help buffer the pH, and keep it in the correct range.
Bugs and Pests
There are too many bugs and pests that will infect your crop. To go into them in one post will be too much, and each bug has to be treated differently. Because of this, you can find guides to each different bug, in our bugs and pest section, but here you can find common things to look out for.
The first sign of bugs in your grow room will be bite marks, and these will depend on the size of the bugs. Look out for small white dots, or patches that look like dry spit. Thrips and spider mites are the most Common Cannabis Plant Problem, when it comes to bugs.
You should always have some sticky traps in your grow room, check these for any insects that may have been caught. Most bugs will lay eggs and live underneath the leaves. Check the underside of your leaves thoroughly for anything that doesn’t look right.
The solution to the pest problem will depend on what insect it is. By keeping a clean and tidy grow room, and using integrated pest management (IPM), it should be rare you see bugs on your plants. Always use sticky traps, and spray neem oil around your grow room, once every ten to 14 days.
Most pest problems can be treated with neem oil, and by keeping a good environment in your grow tent. Enough fans will prevent bugs from laying eggs, so improve the air circulation of the grow room, by adding a few more fans.
To get the best diagnosis and treatment for a bug problem on a cannabis plant, sign up to our forum and ask for help in the pest section, or see our category on pests. Most bug issues can be solved within a week, don’t panic, it can be fixed.
Heat stress is usually caused by high humidity, and poor air circulation. The plant needs the right environment to breathe. If it is too humid, the plant can not evaporate moisture from is pores, and it will begin to suffocate.
Heat stress will first show signs that look like nutrients excess. This is when the tips of the leaves begin to curl up. But, not only do the tips curl up, the sides of the leaves will too, this is called “canoeing”. Your plant will look like it is suffering from nutrient excess, but there will be no nuit burn.
Improve the airflow in your grow room and ensure temperatures and humidity are kept at optimal levels.
Another reason you may see heat stress is because your lights are too close to your plants. Always ensure that with HID and LED lighting, that there is around 40cm, or 18 inches between the lights, and the top of your plants.
As a root ball on a cannabis plant grows bigger, it will need more space. If a plant isn’t transplanted, the roots will grow longer, and longer, until they start to strangle themselves. This is known as being root bound.
It is difficult to tell if a plant is root bound, without looking at the roots themselves. The plant will display signs of under watering, and nutrient deficiencies. The best way to tell if a plant is root bound, is by looking at the roots.
In hydroponic systems, this will not be too difficult, but for soil or coco growers, you may have to lift the plant out of its pot to check. Do this carefully, and take your time, cause as little disturbance to the plant as possible.
If the roots are wrapped around the bottom of the pot, then the plant is starting to become root bound. If there are so many roots that they form a mat at the bottom of the pot, you may have to trim them before transplanting.
Check the bottom of your pots regularly, so you can see the holes. If there are a lot of roots poking through these holes, you should transplant straight away. Do not leave it too long, as the roots will grow quickly and become root bound easily.
Remove the plant from the pot, and trim the roots if necessary. Then, place the root ball into a bigger pot, with some fresh medium. Add some good bacteria to your water, and water the plants to help them sit into their new medium.
Final Notes on Cannabis Plant Problems.
These are just a few of many problems that can arise while growing cannabis. But there are the most common. If you’re plants are suffering with any problems, you can find help in our forum!
Thanks for reading! You can find more information on anything related to growing in our cannabis grow guides. All of our guides are written by experienced growers, and members of our cannabis growers forum. If you have any questions, sign up. It is free, and we are always happy to help!
Thanks for reading Percys Growers, stay safe, and as usual Happy Growing
12 thoughts on “Common Cannabis Plant Problems and Solutions”
@percysgrowroom this is soo helpful thanks Macky for the sterling work
Thanks man, glad you like it mate, hope you never need it 😉
@percysgrowroom amazing article. Haven’t found anything as descriptive and all in one place.
@artmann, yes it looks like your locked out. This problem has been going on for awhile now with that must affected material. Your got a Mag defis probably from too high EC. Drain and flush plants. Pour 1/2 gal to 1 gal fresh RO water with 3ml Cal/mag over net pot/top of roots. Change out nutrients solution and bring EC back in at 1.0. Let them stabilize for a few days and increase EC gentle over the next week. Mag deficiencies takes a couple of weeks to show themselves and just as long to see improvements. The leaves won’t repair but don’t cut them. The plant will use what ever is left in them and they will drop when done. It won’t be pretty but you’ll get across the finish line. At this stage in flower she/they could need 3-4ml or more of Cal/mag pre gal, 4-6 week of flower, right?
If your pushing her hard you may have locked out the mag with too much PK which is usually the case. Very common. So, flush and replace at lower EC with more Cal/mag. Lower PK till she say’s different.
Here’s a few shots. I scoped for pests. No bugs. Looks burnt.
It would be easier to diagnose with a picture of the whole plant. 2 things stand out to me. There are tiny dots on the leaves that look like insect damage? The edges look like nutrient burn imo. Seeing the whole plant would put everything in context better.
What do I have here?
Switched to Jack’s 321. Been running lighter than most. 650 ppm. Greengenes mix.
Is this nutrient toxicity?
@percysgrowroom super read!
@monkeydo, she’s in organic potting soil, feeding Advanced Nutrients, fed her last night, b4 that she was fed on 12/29/20, ph was 6.5. hoping the nutes give her the boost she needs! ive included a better picture of the problem areas. Thank you!!
Looks like something in that magnesium area but it’s difficult to see in the blurple light. It doesn’t look to be in flower. What’s the plant growing in, soil, coco, rock wool, dwc, and what and how much are you feeding it if any? What’s the ph of the feed water? She doesn’t look that bad yet, just have to get her happy again.
noticed brown spots along upper leaves, unsure if this is Manganese deficiency or not? any suggestions? she is 37 days old; get confused between Magnesium (MG) and Manganese (MN) both have Iron Zinc properties in the growth process that can be deficient. Your expertise is much appreciated! Stay Lifted