Why are my Cannabis Buds turning Gray?
If your flowering cannabis buds are turning grey, they're being attacked by a fungus called Botrytis (aka bud rot). If your plant stem is turning black or a dark color, that's most likely bud rot too. Believe me when I tell you that bud rot is not something you want to deal with. It will devour your largest cannabis colas like a fat chick gone vegan. Botrytis on cannabis progresses very rapidly and each day you will notice previously fresh, clean buds turning grey or brown. Bud rot sucks but as you'll read there are ways to prevent bud rot and a few things you can do to get rid of bud rot if you already have it.
What causes Bud Rot?
Botrytis likes an atmosphere with high humidity and lower temperatures. Low airflow also helps bud rot form. For outdoor marijuana growers in California like us, late-summer humidity or rain showers is bad news for our flowering cannabis plants and we need to be vigilant to make sure Botrytis doesn't attack our plants.
How to spot Botrytis early
Identifying Botrytis early is critical to avoiding a cannabis catastrophe. The earliest sign of Botrytis is a single brown leaf tip protruding from your bud. The leaf is brown because it's dead. Note that this looks very similar to the signs of caterpillar damage, so you'll need to pull the bud open to know whether it's Botrytis or budworms. In some cases it could be both, where the caterpillar ate and damaged your flower, pooped, then Botrytis got tagged-in and took over.
Pull the bud open and inspect it. Bud rot is gray and mushy. Remove bud rot if you find it per the instructions below.
Pull the bud open and inspect it. Bud rot is gray and mushy. Remove bud rot if you find it per the instructions below.
Ways to Prevent Bud Rot
As mentioned in my #1 Rules for Growing Outdoor Marijuana Organically, you should never spray your flowering plants with anything, including insecticides, when the outdoor humidity is high. If it's very humid outside and you decide to spray the buds of a late-flowering cannabis plant, you're basically just growing Botrytis at that point instead of cannabis. DO NOT ADD MOISTURE TO BUDS THAT ARE LATE INTO FLOWER IF IT'S HUMID OUTSIDE.
Another good way to prevent bud rot is to grow cannabis strains that are less likely to get bud rot. As noted on the Should I grow Cannabis Clones or Seeds page, I recommend growing outdoor strains with earlier harvest times (also referred to as shorter flowering times. The less time your outdoor cannabis has to grow, the less chance it has to encounter higher humidity, lower temps, and rainfall. For further bud rot prevention, you should grow a cannabis strain that doesn't have dense buds and is rated well for mold resistance. Dense marijuana buds trap and retain more moisture and don't allow as much air circulation as a lighter, fluffier bud. Determining whether a particular strain of cannabis will have lighter buds or whether the strain has good mold resistance is not always easy to find out, even for experienced growers. Usually the strain description will just say that it's recommended for novice growers, and for your first time growing cannabis I would urge you to grow those outdoor strains.
Botrytis likes to colonize on dead plant matter. For that reason, you should remove any dead leaves or stems on and around your plant. Sometimes you'll have leaves fall off your cannabis plant, but the stem remains. Remove those stems to prevent Botrytis from setting up camp close to your buds.
Finally, remember to keep your gardening tools and hands clean. Wash your hands before moving between plants and clean your garden tools regularly with alcohol or hydrogen peroxide. Remember that the fungi and molds that attack your cannabis plants are microscopic and will happily hitch an invisible ride on your dirty trimmers from plant A to plant B.
Another good way to prevent bud rot is to grow cannabis strains that are less likely to get bud rot. As noted on the Should I grow Cannabis Clones or Seeds page, I recommend growing outdoor strains with earlier harvest times (also referred to as shorter flowering times. The less time your outdoor cannabis has to grow, the less chance it has to encounter higher humidity, lower temps, and rainfall. For further bud rot prevention, you should grow a cannabis strain that doesn't have dense buds and is rated well for mold resistance. Dense marijuana buds trap and retain more moisture and don't allow as much air circulation as a lighter, fluffier bud. Determining whether a particular strain of cannabis will have lighter buds or whether the strain has good mold resistance is not always easy to find out, even for experienced growers. Usually the strain description will just say that it's recommended for novice growers, and for your first time growing cannabis I would urge you to grow those outdoor strains.
Botrytis likes to colonize on dead plant matter. For that reason, you should remove any dead leaves or stems on and around your plant. Sometimes you'll have leaves fall off your cannabis plant, but the stem remains. Remove those stems to prevent Botrytis from setting up camp close to your buds.
Finally, remember to keep your gardening tools and hands clean. Wash your hands before moving between plants and clean your garden tools regularly with alcohol or hydrogen peroxide. Remember that the fungi and molds that attack your cannabis plants are microscopic and will happily hitch an invisible ride on your dirty trimmers from plant A to plant B.
How do I get rid of Bud Rot on my Outdoor Marijuana Plants?
Because Botrytis moves so rapidly on a flowering cannabis plant, finding and removing it quickly are critical to saving the rest of your plant. I've had bud rot that I caught very early and which only affected a couple buds, and I've had bud rot that destroyed half of my plant. Catching it early is critical, so if you see that single brown bud leaf poking out, inspect it immediately.
To get rid of bud rot on an outdoor cannabis plant:
Please understand that this is not guaranteed to work if you have a lot of rot on your plant. Bud rot on one little bud won't be too much problem, but a large Botrytis outbreak is very hard to get rid of. If Botrytis is firmly established on your cannabis plant, these steps will mostly just slow the progression of it until you can get your plant harvested.
To get rid of bud rot on an outdoor cannabis plant:
- Remove the buds affected by Botrytis
- Carefully cut off any buds that are damaged by the bud rot. Be as delicate as possible to avoid transmitting spores to other areas of the plant. If anything looks suspicious, remove it. Depending on the severity of the outbreak, you might have to remove entire branches to get the bud rot under control. I'm sorry for you but that's what has to happen if you want the best chance at keeping the other branches clean.
- Spray remaining affected areas with a hydrogen peroxide solution
- Mix up a solution that's half water and half hydrogen peroxide (the typical 3% stuff that you get from any drug store). Lightly spray the areas where you cut away the bud rot to kill off the Botrytis spores that are lingering. Remember, if it's humid outside don't spray any areas of dense foliage since you'll just be contributing to the conditions that allow Botrytis to grow. You can also apply hydrogen peroxide directly if you'd like, as long as you're using the 3% stuff and you're not spraying it on the flowers everything should be fine but go slowly.
Please understand that this is not guaranteed to work if you have a lot of rot on your plant. Bud rot on one little bud won't be too much problem, but a large Botrytis outbreak is very hard to get rid of. If Botrytis is firmly established on your cannabis plant, these steps will mostly just slow the progression of it until you can get your plant harvested.