Why are leaf tips brown, burnt, or yellow?
Leaves have burnt tips, yellow tips, brown edges… These are some of the most common symptoms growers see on their cannabis plants. It can be hard to identify the cause because a lot of different things can cause similar symptoms.
Today I’ll break down all the reasons you might see brown tips or yellow leaf edges. Get to the root of the problem and get back to green healthy leaves!
Nutrient burn is a common cause of burnt leaf tips, but not the only one!
1.) Nutrient Burn
There are a few possible causes for discolored leaf tips, but one of the most common is nutrient burn.
This happens when you are giving cannabis plant too high levels of nutrients. Usually, the first signs of cannabis nutrient burn are yellow or brown tips on leaves after increasing the overall amount of nutrients. As time goes on, the brown continues inward and the tips start curling up. The tips will be dry and easily break off with any pressure.
Nutrient burn is brown and appears on the tips of leaves and causes ends to curl up
2.) Light Burn
Plants can get light burn (sort of like a sunburn) even if the temperature is completely under control. The symptoms are usually concentrated close to the grow lights.
A lot of growers don’t realize that light stress (lights being too close) can cause yellow tips. This symptom is often mistaken for nutrient burn. You can tell the difference because the yellow tips on appear on leaves close to the light. With nutrient burn, the tips are usually brown and appear all over the plant.
Yellow tips from the grow light being too close (light stress)
Light burn can cause the leaves closest to the light to turn yellow or brown around the edges
If it keeps progressing, light burn can also cause the edges of leaves to start turning brown
Another example of light burn from the grow light being too close
3.) PH or Nutrient Problem
Certain nutrient deficiencies are often mistaken for nutrient burn.
Here are some common nutrient deficiencies that can also cause burnt or yellow leaf tips and edges. Nearly all of these examples were caused by Incorrect pH (the #1 cause of nutrient deficiencies).
A potassium deficiency causes the edges of leaves to appear burned
Another example of a potassium deficiency
A potassium deficiency is often mistaken for nutrient burn. One clue is the brown edges go in further that nutrient burn, and doesn’t affect tips as evenly.
A potassium deficiency can express itself in a few different ways
A copper deficiency causes dark leaves with yellow edges
A magnesium deficiency can also discolor the leaf edges
The best way to prevent nutrient deficiencies is to make sure you’re giving your plants the right type of nutrients and pH’ing the water to the proper level depending on your growing medium. But that doesn’t mean more is better. It’s important not to overload your plants with too high levels of nutrients.
Too Much Nitrogen (Nitrogen Toxicity) causes dark green leaves that often feel dry and crispy and get discolored edges
What about Calcium deficiencies?
It used to be that a lot of growers thought brown tips were caused by a Calcium deficiency. However, we’ve since learned that’s incorrect. Here is what a real Calcium deficiency looks like.
Calcium deficiencies don’t cause brown tips. This is a calcium deficiency.
Another example of a calcium deficiency (no brown tips). It mostly affects the middle of leaves.
4.) Heat Stress
Even if your grow light is a good distance away from your cannabis plants, they can still get stressed out by too much heat. Cannabis plants generally prefer temperatures under 85°F / 30°C, though some strains are more sensitive to heat (shorter, bushier strains are often more sensitive to heat than the longer, lankier strains).
Most plants are fine with a few hot days, but if it’s hot every day for weeks, your plants can really start to suffer. Most marijuana plants can handle a small heat spell, but they don’t want to live in a desert! Learn 5 secrets to controlling heat in the grow room.
Heat Stress can burn leaf edges
The following plant experienced 100°F (38°C) temperatures for several days during a heat wave. Burnt leaf tips doesn’t even begin to describe what happened to this poor plant.
An extreme case of heat stress
5.) Root Problems, Root Rot or Bad Watering Practices
Chronic overwatering can sometimes cause unusual deficiencies even if the pH is spot on, like this plant grown in muddy soil. The biggest sign that these symptoms are caused by overwatering and not pH (or something else) is that the plant is always droopy.
Another example of a deficiency that’s actually caused by overwatering (notice how this seedling is also droopy)
6.) Bugs or Pests
If you ever experience a big infestation, bugs and pests can cause a surprising number of symptoms including burnt leaf tips or edges.
Fungus Gnats are one of the most common. They look like tiny flies buzzing around your topsoil. Although a few fungus gnats won’t really hurt your plants, a ton of them will damage the roots, causing symptoms similar to other types of root problems. This can include brown or burnt leaf edges.
A bad fungus gnat infestation can cause a variety of symptoms
Leaves with brown tips, burnt tips, and yellow tips can be hard to diagnose because so many problems can cause similar symptoms. Once you know the cause it’s easy to fix, but if you don’t know it’s impossible! I hope this article helped you figure out what’s causing your symptoms so you can get back to growing.
Why are leaf tips brown, burnt, or yellow? Leaves have burnt tips, yellow tips, brown edges… These are some of the most common symptoms growers see on their cannabis plants. It can be hard to
Quick Summary: Nutrient burn or fertilizer burn is one of the most common beginner cannabis growing problems. The yellow or brown leaf tips are caused by too-high levels of nutrients at the roots, which disrupts the flow of water through the plant and causes the symptom of burnt tips on leaves.
(Nutrient burn is often called “Nute Burn” in the cannabis growing community).
When the roots take in more nutrients than a cannabis plant can use, the overabundance causes problem with water flow in the plant, triggering brown or bronze “burns” on the tips of your leaves. If nutrient levels are not lowered, the burnt tips start traveling inwards and the ends of leaves start becoming crispy and twisted.
As nutrient burn progresses, the tips start getting bronze, crispy, curled and sometimes twisted. Although you can stop nutrient burn from getting worse, the burnt appearance won’t go away on the leaves that were already affected.
Nutrient burn is most common when feeding cannabis too-high levels of bottled nutrients and especially chemical or mineral nutrients. This is what you’ll find in most non-organic plant food.
Mineral-based nutrients can help increase cannabis growth rates and yields compared to organic-based nutrients due to the fact that these nutrients are so easily absorbed by the plant roots. The plant doesn’t have to do any “work” to get the nutrients. The downside is your plant can easily take in more than it can use if the nutrient levels are too high.
Nutrient burn affects the tips of marijuana leaves. You may just see it on one or two leaves, or it can appear all over the plant.
Nutrient burn can also happen when plants or seedlings are grown directly in soil that has a high level of nutrients (a “hot” soil or growing medium) such as fresh compost, manure or a nutrient-amended soil mix. This usually happens to young seedlings, and they will “grow out of it” as they begin to use up all the nutrients in the soil, as long as more nutrients are not added.
In general, plants use overall higher levels of nutrients as they get more light. Therefore plants in relatively low light conditions can get nutrient burn at lower levels of nutrient than the same plant would under bigger grow lights.
Each cannabis plant is different, so you might have just one out of many plants get nutrient burn! That is completely normal.
Sometimes you’ll also see nutrient burn leaf tips also curl or “claw”. The clawing can be caused by an overabundance of Nitrogen (Nitrogen Toxicity), which is common for plants that are experiencing nutrient burn from overall high levels of nutrients.
Problem: You will notice the tips of your marijuana leaves showing the first signs of nutrient burn by turning yellow, tan, gold or brown. A light case of nutrient burn will only affect the tips of your leaves.
The yellow tips will eventually turn rusty brown and crispy. If you do not correct the problem, you may also notice the burn slowly spreading from the tips to the whole leaf. At this point, if you haven’t done so already, you should immediately treat your plant (directions below) before there’s more damage.
Nutrient burn can also manifest itself as brown or bronze spotting around the edges of the leaf serrations (often when there’s a problem with proper absorption of potassium), or with leaf tips curling downwards (tips pointing down is often associated with too much nitrogen).
Nutrient burn causes tips to start curling up if it gets bad enough
These Are NOT Nutrient Burn!
(Sometimes Mistaken for Nutrient Burn)
Light Stress can cause yellow tips or edges, which can sometimes be confused with nutrient burn
This is actually a Potassium Deficiency, not nutrient burn!
Why Growers Should Try to Prevent Marijuana From Getting Nutrient Burn
I have heard some growers say that a little nutrient burn is actually a good thing, because it means that you are giving your plant the highest level of nutrients it can use. A lot of growers have the mistaken idea that nutrients are somehow “food” for your cannabis plants, and so more food = more energy = bigger yields.
This is wrong, instead nutrients are more like a multi-vitamin for your plant. Just like you can’t give a child 10 multivitamins a day to make them grow faster, you can’t give your plants 10x the regular does of nutrients and expect anything good to happen.
The real “food” for your plant is light. Your plant produces energy from light through a process known as photosynthesis, which is most effective when the plant has healthy green leaves.
Your leaves are like solar panels, and the energy produced by the leaves is used as energy for the whole plant. You need the leaves to be in tip-top shape to get the most energy from the lights, so your plant has plenty of energy to grow and produce buds.
Therefore, the biggest problem with nutrient burn is the fact that you are losing leaf mass and overall leaf robustness on your cannabis plant.
A little nute burn won’t slow down your plants much, if at all, but if nute burn is left out of control, you will begin to lose serious leaf mass and it will dramatically slow down plant growth and reduce your overall yields.
What’s worse, if excess nutrients are not flushed out of the plant’s system before harvest, the buds may contain trace amounts of extra nutrients, giving the buds an unpleasant chemical-like taste. Speaking of the flowering stage… (Wait, what’s the flowering stage?)
Nutrient Burn is More Serious in the Flowering Stage
Cannabis plants spend the beginning part of their life in the vegetative stage. When cannabis plants enter the second part of their life, the flowering stage, they stop focusing on making leaves and stems, and put all their focus on making buds/flowers.
The flowering stage is the most vulnerable stage for cannabis plants, because they don’t have much ability to bounce back from any problems.
The further you get into the flowering stage (and the closer you get to harvest), the less likely the plant will replace a leaf that is damaged or dies. By the time harvest is around the corner, your plant basically stops making any effort to recover from leaf damage, and its complete focus is on fattening buds.
That’s why budding cannabis plants need extra care to thrive – in the flowering stage, a little bit of nutrient burn will probably be okay, but too much nutrient burn can seriously hurt yields because the plant will not be able to recover. If you are adding nutrients to your water, it can be very easy to burn your plants in the flowering stage (even with nutrient levels it was fine with before) as different strains have different needs throughout budding.
Solution to Cannabis Nute Burn
If you are using bottled nutrients – Most people who get nute burn are feeding their plants extra nutrients in the water. First off, make sure you are using a quality set of nutrients that has been specifically designed for cannabis plants. Any nutrient system designed for plants like a tomato will also work in a pinch. Also make sure you are feeding nutrients for the right growth stage – for example, all cannabis nutrient systems have you feed different nutrients for the vegetative and flowering stage. If you are feeding the wrong type of nutrients for the stage your plant is in, that is an easy way to give your plants lots of nutrient problems including nutrient burn.
If you are using the wrong type of nutrients for a plant like cannabis, you will eventually run into nutrient problems, one way or another.
Many nutrient systems come with instructions to feed your plant more nutrients than most plants actually need. It’s good business for the nutrient companies if you use more nutrients. However, in my experience it’s a good idea to view the feeding charts that come with any nutrient system as the maximum amount of nutrients and actually start with much lower levels. I tend to start with half the recommended amount, and slowly work my way up only if needed.
Hand-watered system – If you are growing in a handwatered system (like in soil or coco coir), flush your system with plain, pH’ed water if you notice the first signs of nutrient burn. (Learn about pH). If you are not adding any extra nutrients in your grow, then you simply need to wait until the plant uses all the excess nutrients in the soil – after the nutes have been used up, the plant will naturally get over the nute burn (old leaves won’t recover, but leaves should no longer be getting new brown or burnt tips).
Hydro system – Reduce the overall levels of nutrients in your water reservoir by either adding plain pH’ed water to dilute the water, or you could also mix up a new set of nutrients (at lower levels) and completely change the water.
Be careful not to make big changes too fast, it’s better to go relatively slowly in hydro.
In hydro, once you change the water and lower the nutrient levels to an appropriate level, you should immediately notice the nutrient burn stop spreading. Old leaves won’t recover, but you shouldn’t notice any leaves getting worse.
If you don’t have a TDS meter to measure the levels of nutrients (and other extra stuff) in your water, I would normally start your plants with a fraction (perhaps 1/2) of the nutrients you were giving them before – and then work your way up to higher nutrient levels only if you notice the lower leaves are starting to yellow too quickly (nitrogen deficiency). Even then, try to move up nutrient levels as slowly as you can. If you lose leaves to a nitrogen deficiency from slightly too-low nutrient levels, you will lose a few of the least important lower leaves. But if you raise nutrient levels to fast and get nutrient burn, all the leaves on the whole plant will be affected and never recover fully.
One of the things that can be frustrating about hydro is that different plants or strains will be okay with different amounts of nutrients. You can be giving 2 plants the exact same levels of nutrients, and one might get nutrient burn while the other plant is getting a deficiency at the same level. This is because different plants absorb the nutrients at different rates.
Plus, plants drink more or less water depending on the temperature and humidity of your grow area, so even if you’re familiar with the nutrient levels of a particular strain, it can be hard to keep track of the exact right nutrient levels until you get familiar with your setup, unless…
Luckily, there is an awesome tool to make this much easier in hydro.
In hydro, it is very helpful to get a tool called a TDS meter to help you regulate the amount of nutrients in your water. A TDS meter will be able to tell you how much “stuff” is in the water, and whether the levels of nutrients are getting higher or lower each time you check. You can test your reservoir at any time to see if the levels of nutrients are rising, so you’ll be able to stop nutrient burn before it even affects your plants.
To find out more about using a TDS meter to measure nutrients in your water, check out our article: PPM: What It Is and How To Track It.
Could your cannabis also be suffering from Nitrogen Toxicity? – Nitrogen toxicity is common on cannabis plants with nutrient burn
Are the ends of leaves curling like a claw or pointing down like talons? If your plant is experiencing “the claw” and not just normal drooping like from underwatering or overwatering, then you may have a nitrogen toxicity (too much nitrogen).
These Plants Are NOT Overwatered, These Leaves Show Signs of Nitrogen Toxicity
Learn more: Nitrogen Toxicity
(“The Claw”, tips bent down, curling / clawing, dark green leaves)
Nitrogen toxicity is relatively common with plants experiencing nutrient burn.
Nutrient burn causes the tips of cannabis leaves to turn yellow or brown. The burnt tips are the result of too-high levels of nutrients. Learn how to fix it!