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How to Spot the 7 Most Common Cannabis Plant Deficiencies by Leaf Symptoms

A cannabis plant is hardy, but its health and vigour will be negatively impacted if it is deprived of essential nutrients. If this is not corrected, it can cause plants to stop growing or even die. Deficiencies in cannabis can be hard to identify, so we have compiled a basic list of what to look out for if things go wrong, and how to fix them.

New cannabis growers are bound to come face to face with a problem or two. Thankfully, cannabis plants are resilient and can stand up on their own in the face of pests or improper growing conditions for a while. But if the problem isn’t rectified in a timely manner, there’s going to be consequences.

One of the biggest mistakes new growers make is overreacting, though. If an iffy situation is spotted, growers should simply acknowledge that and take the time to learn what the problem is and how to properly fix it.

This guide will go over some of the most common problems that can be identified by simply inspecting the leaves. It also will explain how to proceed and get those plants on the road to recovery… and a better yield!

While this definitely isn’t a conclusive list, here are some common growing problems and how they may be identifiable on cannabis leaves (read the rest of this guide for more in-depth help):

  • Yellow leaves: Could be a sign of all deficiencies mentioned below, or light burn
  • Leaves that curl upward: Could be a sign of potassium deficiency, or overwatering
  • Brown leaves: Could be a sign of phosphorus, potassium, magnesium, sulphur, manganese deficiency. Could also be nutrient burn (more solid brown colouring) or heat stress (brown on the edges)
  • Leaves droop: Could be a sign of overwatering
  • Leaves curl downwards: Could be a sign of potassium or phosphorus deficiency, or overwatering

Nitrogen deficiency in a cannabis plant

Nitrogen deficiency is probably the most common deficiency reported by cannabis growers. It’s usually easy to identify and correct as soon as it becomes apparent, although it shares a basic resemblance to several other deficiencies in the early stages.

In the early stages of nitrogen deficiency, leaves appear to be too light in colour—almost yellowish-green—compared to the desired deep green of healthy leaves. Nitrogen-deficient leaves also typically have slightly darker veins compared to the very light colour of the leaf tissue itself—although the contrast is not as marked as in some other deficiencies.

At the other end of the spectrum, nitrogen toxicity results in leaves taking on a very dark green hue that can look almost black in extreme cases.

In severe cases of nitrogen deficiency, the leaves appear lighter and lighter in colour, and eventually begin to dry out and die. The larger leaves on the lower and outer parts of the plant are often the first to be affected and the first to die.

How to fix nitrogen deficiency

If nitrogen deficiency becomes apparent in the later stages of flowering, it doesn’t need to be corrected. In fact, it’s natural for the older leaves to drop off and die at this point as they are no longer needed.

However, a nitrogen deficiency in vegetative growth or early flower can severely impact overall yield and quality, as it affects the plant’s ability to photosynthesize energy. Nitrogen deficiency can usually be corrected by simply increasing the strength of your normal NPK-based feed, but if fine-tuning is required then nitrogen-only additives are not hard to find.

Phosphorus deficiency in a cannabis plant

Phosphorus deficiencies are rare, but should be cause for concern. If it affects plants in the vegetative stage, it can cause reduced growth rates, small leaves, weak roots, and plants that are generally lacking in vigour. In the early stages, phosphorus deficiency usually causes leaves to appear dark but washed-out, with very dark veins and somewhat lighter leaf tissue.

As it progresses, purplish discolourations begin to appear on the main part of the leaves and the leaf edges begin to turn brown and curl downwards. The leaf petioles (the small stalk attaching the leaf to the main stem) may also begin to turn a purplish colour. In the final stages, large patches of the leaves become purplish-brown and dead, while the remaining sections turn mottled yellowish-green.

Again, phosphorus deficiencies usually affect the outer, lower leaves first. Unlike nitrogen deficiency though, phosphorus deficiency at any stage is cause for concern, as the plants continue to require high levels of phosphorus throughout the flowering period.

How to fix phosphorus deficiency

There are several ways you can fix a phosphorus deficiency. Just remember to take it slow. If any remedy is overdone, the plant could end up not getting enough of other nutrients and fare worse than if it had been left alone. With that said, here are a few methods for fixing it:

  • Temperature – Don’t let the temperature drop below 15 degrees Celsius, as colder temperatures make it difficult for cannabis plants to absorb phosphorus.
  • Water correctly – Ensure the plants are watered correctly. Too much water and soil that’s too packed can lead to a phosphorus deficiency.
  • pH Products – Use a pH up or pH down to ensure the roots have the correct pH level. It should be between 6 and 7.
  • Add Phosphorus Sources – Add sources rich in phosphorus to the soil. Some sources that can be used are fish meal, warm casting, soft rock phosphate and crab shell. (Or simply use a good organic fertilizer that automatically ensures balanced soil)

Once the problem is corrected, new leaves shouldn’t show the discolouring signs of phosphorus deficiency. Keep in mind that old leaves will likely not recover and that’s perfectly normal.

Tutorial: Cannabis plant nutrient deficiencies can be hard to identify. Use this guide to help you figure out what’s wrong and how you can fix it.

Leaf Septoria – An In-Depth Guide To Yellow Spots On Cannabis Leaves

There’s nothing worse than taking a routine look at your plants and spotting anything but beautiful, healthy green leaves. Discovering yellow spots or brown and black spots on leaves can be discouraging, to say the least. Luckily, it’s just a sign from the plant showing you that changes need to be made. If leaves could talk, this is how they’d do it. Leaf septoria shows up initially as yellowing leaves with brown spots. This plant disease is a fungal pathogen that can affect the growth of your marijuana plants. It’s therefore important to know how to prevent as well as effectively treat it if necessary. Here, we’ve put together an in-depth guide into leaf septoria and everything you need to know about this cannabis condition.

What Is Yellow Leaf Spot?

Yellow leaf spot, or leaf septoria, is a common disease that affects many types of foliage and plants including cannabis. When left untreated, leaf septoria can stunt the growth of the plant and negatively affect the final size and quality of the harvest.

Leaf septoria is caused by the fungus Septoria lycopersici. This fungus is known for originating on dead foliage and is often found in garden weeds, meaning the spores can be transferred quite easily to common garden equipment or found abundantly in outdoor environments. When transferred to cannabis, leaf septoria causes unnecessary stress and hinders the overall growth of the plant.

Cannabis Plant Symptoms

Tips For Identifying Leaf Septoria

If you’re looking to avoid disappointing harvests, you’ll want to keep an eye out for the growth-deterring leaf septoria. Fortunately, it’s pretty simple to identify. If your plant is infected, you’ll find yellow leaves with brown spots on the lower areas first. The spots tend to vary in color but usually begin as uniform yellow circles. Inside the circle, there may be a raised bump, which is actually the spore of the fungus. The affected areas will transform from yellow to brown before drying out and withering to death. Once you’ve identified and confirmed that your marijuana leaves are turning yellow with brown spots, a sure sign of leaf septoria, there are a few ways to treat the disease. Let’s cover these treatment options next.

How To Treat Leaf Septoria

To effectively treat leaf septoria, remember: the condition originates from spores, which makes it easy for them to travel through water, direct contact or wind. So, in addition to treating the disease with one of the methods below, you’ll want to deep clean the entire area along with any tools or materials you’ve been using. The spores are capable of hiding out in winter and re-emerging with the arrival of warmer weather, so it’s important to completely dispose of any of the plant material that’s been affected, too.

Top Reasons Of Slow Growth

Here are a few methods you can use to treat yellow spots on weed leaves, aka leaf septoria.

Remove Infected Leaves

As we’ve mentioned, any infected leaf is carrying a spore of the fungus. The first action you need to take when discovering yellow spots on cannabis leaves is therefore to completely remove every one you find. However, do so carefully. You won’t want the spores traveling to other plants if they’re not infected yet. At the same time, you might want to de-leaf or prune any stems to improve nutrient circulation.

Potassium Deficiency

Improve Air Flow And Temperature And Eliminate Moisture

Because leaf septoria thrives in hot and wet conditions, you’ll want to immediately improve your air circulation. In addition, adjust or monitor the temperature and humidity to remain at 20-25C (68-77F) and 50% respectively. Improving your airflow could be as simple as adding a fan or adding ventilation in heat-retaining rooms. De-leafing will also help, as this allows more air to circulate throughout the plant. These measures are obviously more important to implement in indoors rather than outdoor grows.

Avoid Moisture

What adds to the spread of spores? Excess moisture. Therefore, you’ll want to take a few precautions to avoid any additional moisture pooling up or affecting plants that have leaf septoria. This includes being careful not to spray the plant leaves with water. You may even consider watering less to allow your soil to completely dry out. When you do water, be sure to do so in the morning so that the water can dry out throughout the day in full light or sun.

Mediate Your Soil And Remove Weeds

If you’re growing outdoors, you’ll want to mediate your soil to ensure you’ve eradicated leaf septoria spores completely. To do so, rake the area and remove all vegetation or leaves that may have fallen from the plants and weeds in the ground. If you can, let the area dry out as much as possible. Once dry, add a layer of mulch, which will help protect the emergence of the spores again. After your harvest is complete, you may want to move your growing area completely or else replace all the soil.

Best Soil For Growing Weed

Apply Anti-Fungal Sprays

Copper-based fungicides and broad-spectrum fungicides can be effective at eliminating the spread of the leaf septoria fungus. These options can also be used as preventative measures, too. A more natural option that could help treat the spread of leaf septoria is neem oil. Be careful with the application of neem oil, however, as you won’t want it to get on your buds. It can leave an unpleasant taste and smell.

How Do I Prevent Leaf Septoria?

To avoid finding yellow spots on weed leaves or preventing the spread of leaf septoria there are a few measures you can implement. First, be sure you monitor your environment for proper air circulation, temperature and humidity levels. This includes avoiding extra moisture, watering in the morning when possible, and allowing for proper drainage. Of course, keeping your plants healthy is just as important. Leaf septoria is less likely to infect healthy plants or strong genetics that are more immune to detrimental diseases. Purchasing your seeds from trusted breeders will also help you from the get-go. Lastly, begin with fresh soil that has plenty of nitrogen to get off on the right foot with the proceeding crop. Adding helpful bacterias or fungi like Bacillus Pumilis and Trichoderma to your soil is an extra supplement that can promote health and prevent disease.

Finally Armed Against Yellow Leaf Spots

Coming across yellow spots on leaves isn’t a good sign for any cannabis plant, but fortunately, leaf septoria is both treatable and preventable. As always, it’s important to take preventive measures and monitor your plants for proper nutrient uptake and normalcy in growth. If you’re not already doing so, make sure you’re taking a good look at your plant’s leaves regularly. Doing so can help you discover leaf septoria early and treat the condition before your crop’s end product is affected.

Coming across yellow spots on leaves isn’t a good sign for any cannabis plant, but fortunately, leaf septoria is both treatable and preventable. Here, we’ve put together an in-depth guide into leaf septoria and everything you need to know about this cannabis condition