Avoid Nutrient Deficiencies in Your Cannabis Plants

Philip Ghezelbash September 5, 2019 0 comments

How can you ensure your plants are healthy, thriving, and free from nutrient deficiencies?

Keeping a plant healthy and flourishing can be quite tricky, especially for those without green thumbs. What are the signs that a plant is experiencing trouble? How will a grower know there are cannabis deficiencies?

Cannabis plants can encounter a range of issues – from insect damage, to mold, to poor nutrient levels. But, while these problems may seem catastrophic, there are solutions to each. Treating these issues correctly can take a dying cannabis plant and turn it into a healthy specimen capable of producing a high yield.

Bud Rot Means the Plant is Garbage

This is the one problem that can’t be solved. Bud rot is cause by a mold that grows on cannabis buds, rendering them useless and dangerous to consume. It is a particularly fearsome condition as mold-ridden buds make spores that can quickly spread to contaminate the entire grow. Even more insidious is the fact that most infections start on the inside of the bud.

Bud rot typically occurs when plants are grown in a high-humidity environment with inadequate airflow. This is an environment in which mold thrives. Unfortunately, as mentioned, bud rot can start at the insides of buds before revealing itself. This means some plants may look perfectly healthy at first glance.

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Since detection can be difficult, it’s advisable to keep indoor grows at a humidity level around forty five per cent during the flowering stage. This can range from forty to fifty per cent without problem. If things get above sixty per cent, mold damage becomes a big risk.

Ensuring that proper airflow reaches the plants will also help to reduce bud rot. If the dreaded mold infiltrates, cut off all buds with visible growth and those nearest to it. This should save your grow and avoid cannabis deficiencies, but be vigilant.

cannabis deficiencies represented by browning leaves

Light Burn Causes Crispy Leaves – and Deficiencies in Cannabis

Cannabis loves light, and typically the more it receives, the better it will grow. However, the plant does have limits and too much light can result in burnt plants.

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Light burn typically turns cannabis leaves yellow and crispy. The stress from too much light can seriously damage the health and production of cannabis plant as these leaves will no longer be able to photosynthesize. Luckily, there is an easy solution. Light burn is typically only seen in indoor plants someone has placed too close to artificial LEDs. The easy fix is to raise the lights.

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A good test for determining light placement: hold the back of your hand up to the lights where your tallest plant reaches, if the light is too warm for your hand then it is likely going to be too hot for the plants. Ultimately, the strength of the grow light will determine the distance from the plant. T5 Fluorescent bulbs will need to be closer than HIDs, for example, because the energy emitted from T5s isn’t strong enough when hung from a distance of over twelve inches (from the plants).

The grower will need to hang HID lights between twelve (400w) and thirty one inches (1000w) away from the plant. LED lights can be especially hard on plants if they are hung too close so position these no closer than sixteen inches (240-400w) and no higher than forty two inches for the stronger models (900w +). High pressure sodium or HPS grow lights generate a lot of heat so must be mounted between six (150w) to thirty four inches (1000w) from the plant.

Light Bleaching Means Unhealthy “Albino” Buds

Light bleaching happens with high-power LEDs and HPS grow lights. This is how growers create “albino” or “white buds.” The bud bleaching is the result of over-exposure to light. A bleached bud also has minimal scent due to the destruction of the terpenes. Bleached cannabis also tends toward very low potency. So, although it may look cool, “white cannabis” is not healthy and is unlikely to offer any medicinal benefits. Sadly, even if the grow is set up perfectly, there is still a tiny chance albinism could affect the plant. Albinism is characterized by a partial loss of chlorophyll (pigments which give plants their green colour). This lack of chlorophyll hinders a plant’s ability to photosynthesize, reducing its chances of survival and dramatically reducing yield.

Nitrogen Deficiency

Nitrogen deficiency can be tricky to diagnose because this is often mistaken for light burn. Much like light burn, nitrogen deficiencies cause yellowing cannabis leaves. The main way to tell the difference is that light burn leaves typically upturn; while nitrogen-deficient cannabis leaves wilt, and fall off. Light burn is also typically first seen at the top of the plant, while nitrogen-deficiency in cannabis starts from the roots up.

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So why does this happen?

Nitrogen is a nutrient key to plant survival and without it, the plant will start to die, with yellowing leaves being one of the early symptoms. Although not all yellowing is a sign of disaster, it’s important to keep in mind that when cannabis buds grow, the leaves may turn slightly yellow as the bud growth saps some nitrogen content.

cannabis deficiencies represented by dying cannabis leaves

But don’t go feeding your plant too much nitrogen to avoid a deficiency. Like all plants, cannabis requires a balance of nutrients. Too much nitrogen will also result in damage. Nutrient burn causes leaves to turn dark green and curl.

Other Nutrient Deficiencies

If the plant has a phosphorous deficiency, it will experience stunted growth and a red coloring on the stem. Another symptom is the darkening of lower leaves. Organic fertilizer containing phosphorous may remedy this issue. Be aware that the damaged areas may not heal. But, the newer growth will be healthier once you’ve cleared up the issue.

A calcium-starved plant could be the result of over-acidic soil. Foliar feeding (applying liquid fertilizer directly onto the leaves) may fix a calcium deficiency. Try one teaspoon of dolomatic lime per 32 ounces of water until the plant’s health perks up. Alternatively, push eggs shells into the soil, around the plant, at the time of planting. This organic practice is often enough to maintain calcium levels.

Insects Can be a Gardener’s Worst Nightmare

While growing cannabis hydroponically can reduce bug damage, insects such as spider mites, caterpillars, and aphids will likely always be a threat.

Spider mites are particularly frustrating for cannabis growers. They can destroy whole crops of plants. Like spider mites, aphids also suck the nutrients from the cannabis plant and cause it to die. These pests normally hide underneath leaves, so make sure to vigilantly check for any creepy crawlies. Aphids and spider mites may be hard to see individually because they are so small, but they breed fast and you will see them clumping over parts of the plant.

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cannabis deficiencies represented by bugs on a leaf

What Can You Do When Insects Cause Cannabis Deficiencies?

One organic option for tackling spider mites and aphids is introducing ladybugs. These red-backed, flying insects prey on both of these pests. For large infestations, however, you may need to try an organic pesticide or insecticide. Caterpillars tend to be slightly easier to treat. Due to their larger size you can simply remove them from the plant and dispose.

Since pests like spider mites and aphids breed fast, you need to make sure you remove every insect from the plant. Neem oil is one herbal pesticide that some gardeners prefer. Extracted from the seeds of the neem tree, the oil has pesticidal and insecticidal properties but it should be used with care.

There are many factors to consider when in keeping cannabis plants healthy. The old adage, ‘but it’s a weed, it will grow anywhere’ is not exactly true when you want to ensure maximal yield. This is a tightrope walk and a labour of love all mixed into one so go forth bravely and grow your own.

Author avatar

Philip Ghezelbash

Philip Ghezelbash is an ex-personal trainer with a science background who currently operates New Zealand's only health specialized writing studio. He is passionate about presenting complex science in an easy to digest manner and is a firm believer that cannabis has substantial potential to be used as a medicine for degenerative disease.