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4 Telltale Signs of Sick Plants

4 Telltale Signs of Sick Plants

It sucks when you have sick plants. It’s similar to having a sick child or a sick pet. It’s hard to watch something near and dear to you become sick and suffer, even if it’s just a plant. Cannabis plants are more than “just a plant”. They are the result of months of blood, sweat, and tears.

Some cannabis plants are heartier than others. Certain strains are more susceptible to rot. Others tend to mold or become infested with mites. It’s important for you to be able to spot the signs of a sick plant, you know, before it’s too late.

Yellow Leaves

Did your plants’ leaves turn yellow all of a sudden? You definitely have sick plants on your hands. Your plants most likely have the beginning stages of rot. Bud rot is easy to fix, as long as you get to it in time. Try turning up the heat a little more. Cold plants are more prone to rot. Make sure your plants are in an environment warmer than 68 degrees F/ 20 degrees C. The humidity in your grow room could also be too high. It may help to trim your plants, so they’re less bushy. Lastly, trim the infected buds ASAP, lest they infect the healthy plants!

Flowers Turning Brown

Are your flowers turning brown and subsequently dying? You could have broad mites. Despite what the name suggests, broad mites are incredibly small and very difficult to see. Mites will make your flowers turn brown and die if they are not taken care of. Take a look at your new growth. Does it look wet and slightly twisted, like a scary old tree? You’ve most certainly got mites. Luckily, there are sprays you can get to treat mites. Make sure you spray them daily!

If your leaves look like this, it's probably a calcium deficiency. Image source:

Dead Spots and Crinkly Leaves

Do your sick plants have dead (brown) spots and leaves that are starting to crinkle up? There’s a strong plant that your plants have a calcium deficiency. Another tell-tale sign is that your plants appear to not be growing, or the new growth appears smaller than it should. Typically with calcium deficiencies there are deficiencies in other nutrients as well. The best way to do this is with a calcium supplement. Your best bet is to use a cal-mag (calcium and magnesium) supplement.

Leaves that are Yellowish Brown Directly Under the Lights

If the leaves directly under your lights are starting to turn an ugly shade of yellowish brown, then there’s a good chance that your sick plants have a case of light burn. This malady isn’t as serious as some of the other ones. This is more common among the older leaves, the ones that have been exposed to light the longest. Light burn is often a sign of a nitrogen deficiency. The best thing you can do first of all is move your lights further away from your plants, or tilt your plants away from the lights. Reducing your light intensity might help, as well as a nitrogen supplelment.

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Do you have any advice for others with sick plants? Tell us in the comment section!

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Comment Section

10 thoughts on “4 Telltale Signs of Sick Plants

By Grass Chief on 9 November 2017

Very helpful and educative post. Like the guidelines and tips shared here to make marijuana plants more greener and better. Exactly cannabis plants are more than “just a plant”. They are the result of months of blood, sweat and tears.

By Stoney smurf on 11 November 2017

The post is very good info that actually works. I always grow organic and i use black molasses non sulpher i use i dime shot to 1 bucket of water every 3 weeks for my cal , mag supplement , it works awesome you can use right through flowering as well.

By jerry on 28 November 2017

The guidance of a sick plant and other deficiencies' would be a nice resource to look at with pictures and a nice chart to resort to when things happen for those who have not experienced any issues(eh,ehm, like that's never going to happen to the new and or inexperienced as well as the pro's) mabey you have a chart on this site I haven't dug that deep yet.

By jerry on 28 November 2017

oops, looks like you already have that here, thank you

By RYNO on 24 January 2018

My plants are showing signs of white powdery mildew. I'm seeing this for the first time and it's my 1st attempt at using grow bags. I've been using apple cider vinager to control the PM but it's becoming a pain in the ass. It appears that it's working at a solution of 1/2 cup A.C.V. - 1 quart water and mist every sq. inch on all the leaves and branches. Just coming into flower and the nitro is gone now 0-10-10 fert from now until the trichomes are ready for harvest.

By Cachadream on 9 February 2018

I had same problem month ago, used spray of 500mls water, 2 table spoons of Soda powder, 2 table spoon of vegetable oil and 1 tea spoon of non harmful washing up liquid (emulsifier)
Spray plants making sure all plant is covered
Spray grow bags generously
Wipe clean your grow room, including trays, etc
Following day flush your plant with water and spray generously but over foliage only (don't wet buds)
Feed your plant, remember you have flushed the soil so must likely will need all-around nutrients
I also used on the next watering a tea spoon of Epson Salts
Up air circulation
Noticed difference on plant on second day, for now seems problem is gone, my baby is happy therefore I am
BTW, I also used healing frequencies, music, rain sounds and lots of Love

By Carol on 30 August 2018

I started my first ever 4 plants in April and they were transplanted the end of May outside. They did great up until a month ago (first part of August) when they developed light green spots on most of the fan leaves but not on the new growth. I couldn't/can't find anything about what is wrong or how to help them. The soil tested a 7ph. I'm stumped

By latewood_ILGM on 30 August 2018


The best way for us to help you is to invite you to join our support forum where we are set up to help you. As a member you can post images and discuss the issue daily with our friendly members or expert staff. Just click FORUM in the upper right corner of this page and sign up! See you there 🙂

By Cotton top on 25 September 2018

Three weeks to harvest help problem with powdery mildew ,reply 😟😟

By latewood_ILGM on 4 October 2018

Cotton top,

Join our forum at: for real time replies to your question. There are commercial sprays, and homemade remedies. Best to throw this out in the forum or search for "how to treat plants with powdery mildew. Look for the cause. There is something off in your grow environment. Good Luck 🙂

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