September 24, 2022

How to spot and fix nutrient burn in cannabis plants

Cannabis nutrient burn (also known as cannabis “nute” burn) is one of the most common problems for beginner growers. These growers want to feed their plants as much nutrients as possible to ensure healthy plant growth. However, this becomes too much of a good thing as excess nutrients build up in the plant and begin to harm it. If left untreated, nutrient burn can kill off an entire plant. However, there are ways to detect this issue and save your plant.

Causes of cannabis nutrient burn

Nutrient burn occurs when a cannabis plants are overfed. Healthy plants need to process and assimilate all of the nutrients that they absorb over time. When there are too many nutrients in the soil, the plant will automatically absorb these nutrients beyond what it can process.

Cannabis plants will push the excess nutrients through the roots, them stems and branches, and then leaves, where they will first build up in the leaf tips. That is why the dying leaf tips are usually the first sign of nutrient burn.

There are several potential sources of nutrient burn during the growing process. These include:

Cause 1: A “hot” growing medium

Growing mediums consist of either soil for traditionally farmed plants, or inert mediums such a perlite for hydroponically grown plants.

A hot growing medium is one that contains too many nutrients for the plant they’re growing. Artificially nutrient enriched soil, fresh manure, or fertilizer all can overwhelm the plant if they’re too strong.

Hot growing mediums are mainly an issue for potted soil plants. Hydroponic setups deliver all of their nutrients using aquaponic solutions, and have no nutrients in the soil itself.

Cause 2: Excess nutrients from growth boosters

Many growers like to boost their plant growth by using a nutrient solution or bottled nutrients. These solutions include growth boosters for plants in their vegetative stage or bloom boosters for plants in their flowering stage. Using too many of these can easily overfeed your plant and hurt their growth.

Cause 3: Dry soil

Dry soil can also cause cannabis nutrient burn. Soil needs to be wet, so that cannabis roots can absorb the nutrient-containing water from the soil. Dry soil causes these nutrients and salts to build up, particularly if the soil is regularly fertilized.

Dry soil may make a grower believe that they are not feeding their pants enough, so that they then overfeed the plants with more fertilizer. These fertilizers build up in the soil until it’s properly watered, flushing into the plant at once.

Cause 4: Overwatering

Overwatering can cause a lot of problems for cannabis plants. Too much water will harm your plant’s roots, as the roots need dry periods to absorb oxygen.

Habitually overwatering plants can also lead to root rot. Root rot is very difficult to fix once it has begun, and often will cause the grower to lose the entire plant.

Cause 5: Low light

Light is what gives plants the energy they need to grow and process nutrients. If your cannabis plants don’t have enough energy to process their nutrients, the nutrients will then build up in the plant. This will cause the plants to get nutrient burn even if they are not overfed.

Nitrogen toxicity

Nitrogen toxicity is a special case of nutrient burn where the plants specifically get too much nitrogen. This nutrient is the main nutrient that plants need during their vegetative stage.

During this stage, plants take in a lot of this nutrient as it’s required to build bigger roots, stems, and leaves. Growers will feed their plants more nutrients during this stage to encourage growth and prevent nitrogen deficiency.

Once cannabis plants reach their flowering stage, they redirect their energy from growing bigger to producing flower buds. In the flowering stage, nitrogen requirements for cannabis plants drop significantly. It now becomes very easy for plants to absorb too much nitrogen.

Inexperienced growers may not realize that their plant’s nitrogen requirements have dropped, and mistakenly feed them a nutrient solution meant for pre-flowering stages.

Growers that reduce their plant’s nitrogen intake may still get nitrogen toxicity. This is because excess nutrients can still be in the soil from previous feedings, especially if they are grown with time-release nutrient capsules.

How nutrient burn damages plants

Cannabis nutrient burn, if left untreated, can stunt the growth of your plants and lead to reduced harvest yields. As previously discussed, excess nutrients absorbed by cannabis plants are first pushed out to the tips of the leaves. If left unprocessed, they will remain in the leaves as they have no place left to go.

The excess nutrients will first cause the tips of the cannabis leaves to wither and turn brown or yellow. As nutrient burn progresses, it will kill off more and more of the leaves.

The leaves of a cannabis plant act as solar panels that absorb the light and energy that the plant needs to grow. If the leaves start to die off, the plant won’t be able to absorb all of the light needed to sustain it, let alone to grow and eventually bloom.

Nutrient burn is more problematic when a plant is flowering

Cannabis nutrient burn is more problematic when the plant is in its flowering phase. During the flowering phase, cannabis plants will direct all of their energy towards producing buds. They will no longer spend their energy growing or repairing branches and leaves.

If leaves die due to nutrient burn while the plant is flowering, its unlikely that the plant will spend energy to replace their dead and dying parts. This can be a problem if enough leaves are lost from the plant, as a plant experiencing nutrient burn may not have the energy to produce significant buds.

Cannabis nutrient burn is easier to fix if found while the plant is in its vegetative stage. During this stage, the plant the plant goes through a large growth spurt, and can quickly replace dead or dying leaves.

Signs of nutrient burn

While nutrient burn is bad for cannabis plants, there are some early signs that can help growers identify this issue. The following are the most common signs of nutrient burn:

Yellow or brown leaves

Nutrients pushed out to the leaf tips will cause the tips and then entire leaves to turn yellow. These leaves will often exhibit brown marks or brown spotting as well. This browning is often known a “burnt tips”.

Leaves bent at 90 degrees

Leaf tips in plants suffering from cannabis nutrient burn will begin to curl. Some tips will look like they’re bending at a 90 degree angle.

Leaves turn deep green

When cannabis plants are oversaturated with nutrients, their leaves will often turn a very dark green. Oftentimes, the leaves will be deep green but with brown or yellow dying leaf tips.

Stalks and branches change color

Nutrient burn can cause the branches and stalks of a cannabis plant to turn deep red or purple.

Nutrient burn vs nutrient deficiencies

The biggest problem when diagnosing nutrient burn is telling the difference between nutrient burn and a nutrient deficiency. This is because there is significant overlap between nutrient burn symptoms and signs of a nutrient deficiency. Even symptoms from other issues such as light/heat stress or ph fluctuations can look like nutrient burn.

Nutrient deficiencies can have many different causes, but the most common ones are nitrogen deficiency and potassium deficiency. Since the symptoms look similar for over feeding and underfeeding your plants, it’s important to monitor your plant’s feeding schedule to help diagnose your problem.

All of these issues (nutrient burn, nutrient deficiencies, light stress, and ph fluctuations) have a tendency to turn leaves yellow. Therefore, when diagnosing nutrient burn, look for other signs of curling leaf tips or deep green leaves.

One way to to determine if your issue is due to nutrient deficiency is to check the Ph level of the growing environment. This can be done by measuring the Ph of your water runoff from the plants.

An incorrect Ph level will interfere with the nutrient absorption of cannabis plants. Incorrect Ph levels are a sign of nutrient deficiency. this issue should be corrected before trying to treat your plants for nutrient burn.

Here are some pictures of these other issues:

Potassium deficiency

Light burn

How to fix nutrient burn

If recognized and treated early, nutrient burn is often fixable. If you determine that your plant has nutrient burn, follow these simple steps to help it recover:

Step 1: Trim away all dead plant material

The first step to recovering your plants is to trim away all dead material. If leaves and branches are dying, they will not recover. They will only drain resources from the plant as it tries to keep them alive. Removing this material will allow the plant to redirect its energy to new growth.

Any dead material also has the potential to rot which can then spread elsewhere. This can lead to issues such as mold or bud rot, which can ruin the whole plant.

Step 2: Flush the plant’s growing medium

This step is only necessary if the plant is being grown is soil. If this is the case, the soil should be flushed with ph balanced water to remove excess mineral nutrients. This will ensure that no remaining nutrients continue to harm the plant.

Its best to flush the soil multiple times to ensure that all excess minerals have been washed out. One can even measure the ppm of the runoff to ensure that everything has been rinsed.

If this plant is being grown hydroponically, then skip this step as there is no soil to flush.

Step 3: Adjust your nutrient levels

Next, diagnose what caused your cannabis plant’s nutrient burn. If it was due to improper watering or from excess growth boosters, take steps to make sure that is not an issue in the future.

If you’ve been feeding your cannabis plants a nutrient mix that is too strong, then you should reduce your dosage of the mix. Find the appropriate nutrient level, and then to be safe, mix the nutrients at 3/4 the dose to ensure that the affected plants recover properly. This will help the plants to gradually nurse themselves back to health.

Step 4: Recover the roots

To help these plants recover quickly, tend to the roots. There are root-specific nutrient solutions which can nurse them back to health and help them recover quickly.

How to prevent nutrient burn

Cannabis nutrient burn can be an inconvenience to fix in your plants, and also has the potential to harm your harvest yields. Thankfully there are a couple of things that can be done to prevent nutrient burn.

Be aware of your plant’s growing stage

As can previously discussed, the required cannabis nutrients for plants can change depending on the growth phase. Make sure that once the plant begins to bud, you switch from a growth oriented mix to a mix of flowering nutrients. Also make sure to flush your soil if you have reason to believe that it is too nutrient rich (especially if nitrogen levels are too high).

Use less than the recommended nutrient levels

Keep in mind that the recommended dose of many fertilizers is often too high, and will tend to over fertilize the plants. Usually the amount recommended is a maximum dose.

Additionally, different plant strains have different nutrient requirements, so there is no “one size fits all” approach to fertilizer dosing that will work. We recommend starting off a grow using 3/4 of the recommended fertilizer dose, and then adjusting based on your results.

Monitor your nutrient levels with a EC/ph meter

One of the easiest ways to check your nutrients is by monitoring the ph levels yourself. If they become unbalanced, this is a sign that you are either overfeeding or underfeeding your plants.

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