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Diagnosing Common Cannabis Problems 

diagnosing cannabis problems

If you are new to growing and gardening cannabis, there is of course a learning curve and potential for many problems. Most new home growers are known for struggling in their garden and getting anxious about what to do, when to do it, and whether they did it “jussssst right.”  If you are a new grower, you may be curious about common cannabis plant problems and how to avoid or diagnose them. Everything from improper watering, to  plant diseases, to pest infestations, to deficiencies and nutrient burn can be a problem for cannabis.

Sometimes there are multiple problems taking place. But nothing is worse for a new grower than over-diagnosing, or incorrectly diagnosing. This leads to compounding problems for cannabis plants and yourself. That’s not to scare you. It’s to get your attention so you can help yourself avoid over-diagnosing and incorrectly diagnosing in your home grow.

For example, a new grower recently overwatered several of their seedlings and clones. The new leaves were yellowing and the top leaves were yellowing. They misdiagnosed it as a nitrogen deficiency and watered in unnecessary nutrients as a result. Then they watered again. This all worsened the problem. A simple mistake of overwatering was misdiagnosed as nitrogen deficiency. This kind of thing happens all the time, but it can be avoided.

If you are new to growing and gardening, there is a learning curve. Most new home growers are known for struggling in their garden and getting anxious about what to do, when to do it, and whether they did it “jussssst right.”  If you’re growing with a hydroponic system, the opportunities for potential cannabis problems increases compared to a simple soil grow.


Regardless of your style of cannabis cultivation, you should know how to diagnose the most common cannabis problems. Different common problems for cannabis plants normally include overwatering, over-fertilizing, under-fertilizing, poor airflow, weak light penetration, light stress, plant pests, plant diseases, hot temperatures over 82 degrees Fahrenheit, drastic humidity fluctuations, low humidity, high humidity, and bad cannabis genetics.

How do you know when your cannabis has a problem?

You’ll know something is wrong with our cannabis plants if you see something “off” or “wrong.” There are many potential ways a suffering plant can present symptoms. However some new growers still feel compelled to diagnose cannabis problems when there are no problems. If it’s not broken, don’t fix it. If your plants are happy and healthy and smell terrific, congratulations you’re doing fantastic!

Overwatering is the biggest problem for cannabis growers. If you overwater, you’ll notice the plant’s leaves will not be able to “pray to the light.” Then the leaves will droop and wilt considerably. The plant’s roots can also suffocate if the plant has been overwatered. Root rot is also a potential cannabis problem if you are overwatering regularly. Once you have root rot, it’s a tall order to rescue the plant and bring it back to health.

Yellowing leaves is a common cannabis problem with many explanations, some good and some bad. If you start seeing yellowing of the leaves, or if you see other discolorations on the leaves, most people immediately try to diagnose a deficiency. This is not a wise first reaction, but it is common.

It’s not smart because it is more than likely you’re simply overwatering. When you overwater, the plant stops feeding and uptaking nutrients.Thus you get some deficiency symptoms like yellowing leaves. The problem isn’t a nitrogen deficiency, it’s an overwatering problem. You don’t need a new fertilizer or a special fertilizer to fix it, you just need to learn to properly water your cannabis.

If you are using a quality and reputable soil and fertilizer, then you wouldn’t have deficiencies. It’s possible, but instead you should always assess your watering practice before jumping into diagnosing specific deficiencies like magnesium deficiency or iron deficiency. Both of these deficiencies do cause yellowing leaves by the way.

Be vigilant and always assess your watering history thoroughly before jumping into deficiency declarations.

As mentioned previously, yellowing leaves is a very common problem with cannabis, but there’s actually several potential diagnoses for it. Yellowing leaves can be a sign of a pest infestation in addition to a sign of overwatering. Or it could be a result of you not ph-ing your water and/or liquid fertilizer. If the ph is too high or too low, yellowing leaves can be a result. Also, yellowing leaves are sometimes perfectly natural. They are to be expected when you’re in the late flower/bloom phase. As the plant uses up all that’s stored in the leaves at the end of their bloom, leaves yellow. When you see yellowing leaves close to harvest, don’t fret, it’s completely normal.

Instead of reacting to cannabis pest and disease problems, be proactive with prevention.

Another big problem for cannabis growers is pests. Pests like aphids, thrips and spider mites can all ruin a home grow quickly if you’re not paying attention or you don’t respond appropriately. Indoor plants can even get mealy bugs, white fly and scale under their leaves. Close attention is required. You have to literally look under the leaves, as well as on top of the leaves. Sometimes you will see markings and etchings on the tops of leaves, or you’ll see leaves that have been chomped on, but under a leaf is where pests run amuck and eggs lie.

In the case of determining which pest is responsible, it should be pretty clear once you view photos online of aphid damage on cannabis leaves, or of spider mite damage on cannabis leaves and flowers. Most pest control sprays target all the main pests mentioned, but sometimes you’ll encounter a pest that doesn’t go away. If that’s happening to you, try an alternative pest killer and give it a go.

You should also rotate preventative foliar sprays, run an Airo Home Hobby air purifier, and use your eyes and hands to spot check your plants regularly. Just because you don’t see them from afar, doesn’t mean they aren’t creeping.

Foliar sprays are either preventative in nature, or they are designed to kill on contact  Some foliar sprays leave a residue, but others do not. Many foliar sprays smell putrid, but if you’re lucky they will smell ok. An air purifier like Airo Home Hobby will prevent powdery mildew, one of the worst plant diseases cannabis growers fight. The Airo Home Hobby air purifiers are extremely effective at preventing powdery mildew outbreaks indoors. Although modeled after the commercial AiroClean420 model, the smaller Airo Home Hobby will clean a grow space up to 12 x 10 x 10 ft. They are easy to use and there’s limited maintenance required.

Hopefully you’ve learned something about diagnosing cannabis problems today!

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