Pay attention that growing marijuana may be subject to special restrictions and regulation in your country or state. Please contact your attorney to obtain advice before cultivating cannabis.
We know one thing for certain: Everyone wants chunky buds! However, with cannabis nutrient deficiency, you will harvest nothing but pea-sized ones. If that isn't bad news enough, remember that mineral-deficient plants are susceptible to pests and diseases, putting yet another constraint to flower development.
Before your cannabis gets in trouble, take a small lesson in cannabis nutrient deficiency, from the principles of cannabis nutrient deficiency identification to treatments and prevention of further issues. Time to refresh some schoolbook memories and become an even better gardener!
Cannabis Nutrient Deficiency Identification Signs
While state-of-the art methods of diagnosis exist, visual symptoms are often the most practical approach in small-scale cultivation, such as the following:
- General discoloration. The first noticeable cannabis deficiency symptoms would be in the leaves. Yellowing or chlorosis, interveinal discolorations, mosaic patterns, or leaf burns are some signs you might see, if your plants are malnourished.
- Leaf deformities. If the nutrient deficiency is quite severe, malformed leaves with shoe-stringing, cupping, or twisting symptoms can appear.
- Growth retardation. Key nutrients play a significant role in growth and development of the plants, so no wonder that stunted and sluggish growth is directly linked to nutrient deficiency in cannabis.
- Inferior buds. Defects in the cannabis plant that are not corrected early on will result in popcorn sized, less potent buds. This is a green thumb's nightmare.
Reasons for Nutrient Deficiency in Cannabis Plants
Cannabis deficiencies are not directly related to the lack of nutrients per se, but often underlying soil issues attributed to the following:
- Acidic soil. Most nutrients are readily absorbable near a neutral pH (6.0-7.0). However, as the pH becomes lower, aluminum and manganese become more available, which can be fatally toxic to the plants. Acidic media also hinder the uptake of calcium, phosphorus, and magnesium by the roots.
- Saline medium. Also known as alkaline or basic soil, a high pH soil medium above 7.0 is also detrimental to cannabis. It reduces the availability of phosphorus and many micronutrients in the rhizosphere, leading to the appearance of symptoms on the leaves.
- Nutrient concentration. Essential elements in plants are categorized into macro and micronutrients, each requiring a specific concentration to be efficiently absorbed by plants.
Types of Cannabis Deficiencies
Each cannabis nutrient deficiencies express unique symptoms and treatments, which you can find in the following:
Nitrogen
Nitrogen is a highly mobile element that forms pillars of chlorophyll and the building blocks of amino acids.
- Symptoms: Chlorosis can mainly be observed on the lower foliage during the vegetative stage, as the plant prioritizes the distribution of the nutrients to the younger leaves. In general, stunted growth and absence of blooms could be the severe consequences of N deficiency in cannabis plants.
- Toxicity: Leaves turn darker with excessive N concentrations and will profusely grow leaves. Weak stems become very prone to dislodging.
- How to treat: Add nitrogen fertilizers in the forms of fish-based foliar sprays, seaweed extract, compost, or well-composted manure.
- How to prevent: Add a few sprinkles of urea pellets in the potting medium or fortify the soil with the organic matter mentioned above.
Phosphorus
Phosphorus is a macronutrient required in the synthesis of structural proteins, amplifying plant DNA copies, and normal photosynthetic functions.
- Symptoms: You can spot purplish to dark-tinged leaves due to the accumulation of anthocyanins. Acute deficiencies in cannabis plants result in cessation of growth, bronzing leaves, necrotic spots, curling, or death.
- Toxicity: Yellowing in between leaf veins of younger leaves, scorched tips and margins can be observed. Plants also begin to grow shorter internodes.
- How to treat: Adjusting the soil pH range to near 6.0 makes the fixed P more available to the roots. P-rich fertilizers like earthworm castings, bone meal, and fishmeal are excellent alternatives.
- How to prevent: Prepare the soil well before planting by amending P from inorganic sources like monoammonium phosphate at the vegetative stage.
Potassium
One of the common marijuana plant deficiencies is potassium, as it executes vital plant processes like water regulation, leaf gas exchange, root development, and cell division.
- Symptoms: Bronzing, sun-burnt appearance, dry leaf edges, interveinal yellowing, and twisting can be seen in the lower leaves.
- Toxicity: Excessive application does not lead to toxicity but interferes with positively charged elements like nitrogen, calcium, and magnesium, rendering them less available to the roots.
- How to treat: Water the media with a pH-calibrated solution to make it more bioavailable. Actively adding K fertilizers (chicken manure, seaweed extract, potassium nitrate) as top dressing can also provide the same benefits.
- How to prevent: Test the soil's K content. Sprinkle K fertilizers just before the flowering.
Calcium
Calcium’s indispensable duty is to thicken the plant cell wall. Physiologically, it aids in the intercellular transport of nutrients like carbohydrates and nitrogen.
- Symptoms: Weak, thin stems and lack of flowers are the main symptoms. Lower, older leaves can collapse and/or develop sporadic brown spots.
- Toxicity: Might raise the soil’s pH, resulting in micronutrient lockout, including magnesium, potassium, phosphorus, copper, zinc, iron, and boron.
- How to treat: Apply a Cal-Mag solution. Adding dolomite lime or using calcium nitrate fertilizer can also be beneficial to your greenie's health.
- How to prevent: Add a few spoons of powdered limestone to the potting mix or use calcium-based fertilizers prior to planting to prevent weed plant deficiency.
Sulfur
Sulfur makes up the chemical backbone of enzymes and proteins. Also, it has an irreplaceable role in the metabolism of lipids in plants.
- Symptoms: You will notice younger leaves becoming paler and eventually turning yellow. Plants grow weak and thin, slowly becoming incapable of producing potent buds.
- Toxicity: Prevalent in hydroponics (rarely occurs in cannabis), but overdose of the element interferes with the absorption of other nutrients by depriving root respiration.
- How to treat: Apply sulfur plant sprays, powdered elemental sulfur, or ammonium sulfate fertilizers.
- How to prevent: To avoid cannabis plant deficiency, adjust the soil’s pH (i.e., use neutralizing products like lime or organic matter).
Magnesium
Magnesium deficiency is mainly observed in the leaves because it is essential in building the green pigment chlorophyll.
- Symptoms: Mature leaves at the lower part develop yellowing in between veins. As the plant begins to lose its ability to photosynthesize, spots may also appear.
- Toxicity: As a result of overapplication, stunted growth is observed. Similar to salt toxicity, the foliage turns dark green.
- How to treat: This cannabis leaf deficiency is often treated with Cal-Mag or Epsom salts. Foliar fertilizers with Magnesium could also provide similar effects.
- How to prevent: Amending the potting soil with compost to neutralize the pH and with a few sprinkles of Epsom salts makes Mg more readily accessible to the roots.
Manganese
Manganese is responsible for the routinary physiological activity in cannabis, primarily with nitrogen transport, leaf “breathing,” carbohydrate assimilation, and root development.
- Symptoms: Mn problems can be recognized by chlorotic leaves, interveinal or uniform, that later develop necrotic or dark spots.
- Toxicity: Mottles or bronze mosaic patterns on the leaves develop as Mn concentration increases in the soil. The symptom slowly progresses to the older leaves.
- How to treat: Mn deficiencies are often linked to off-balanced pH, so a good neutralizing solution such as humic acid could resolve the issue effectively.
- How to prevent: Prepare the soil well by incorporating organic materials that buffer pH changes.
Boron
A common soil element, boron rarely causes deficiencies, but its absence could lead to reduced cell division and weakened cell walls.
- Symptoms: General wilting, twisting, and bronzing of interveinal leaf spaces are common symptoms of boron deficiency. Typically, both stems, and roots grow less vigorously.
- Toxicity: The leaves turn yellow, with a distinct gradient starting from the top, and eventually drop.
- How to treat: Flush the pot with an acid-correcting solution and apply light, heavily diluted boric acid.
- How to prevent: The issues can be prevented by proper media preparation and infusion of organic matter.
Iron
One of the micronutrients linked to weed deficiencies is iron, as it is directly involved in manufacturing leaf pigment, functional enzymes, and respiration.
- Symptoms: Watch out for yellowing of young leaves and dark green appearance of veins, resembling magnesium deficiency, later progressing to the old leaves.
- Toxicity: Rusty or brownish leaves on top, reminiscent of phosphorus deficiency.
- How to treat: You can fix the pH imbalance by putting a layer of compost on top of the soil or flushing the media.
- How to prevent: Ensure enough drainage, use well-decomposed manure, and avoid over-supplying micronutrients like copper. We recommend choosing a mixed medium rather than clay or reddish soils.
Silicon
Silicon is the primary component of sand, making it quite unlikely to cause deficiency symptoms in cannabis growing.
- Symptoms: Pay attention to general deformities of the leaves.
- Toxicity: Typically, the leaf margins dry out.
- How to treat: Add silica sand or silicate minerals to the soil.
- How to prevent: Add sandy materials and a proportionate mix of other components.
Zinc
When it comes to the league of micronutrients, zinc is amongst the common weed plant deficiencies because it is essential in the secretion of growth hormones and proteins.
- Symptoms: Signs of chlorosis can be noticed on freshly emerged leaves, often in between the veins.
- Toxicity: Excesses of zinc levels are uncommon, typically characterized by sudden appearance of symptoms similar to those in iron-deficient plants.
- How to treat: Use foliar sprays of chelated zinc. Other all-purpose fertilizers with high enough concentration can also be considered.
- How to prevent: Lower the pH in saline soils by applying sulfur, avoid overwatering, use seaweed foliar spray.
Copper
Copper is a micronutrient involved in enzymatic and photosynthetic activities. It infrequently occurs in most soil types, even well-prepared mediums.
- Symptoms: Weed leaf deficiencies can be identified by the discoloration of the young foliage, also typically developing a bluish or mauve tinge.
- Toxicity: Reduced plant growth is usually observed.
- How to treat: Restore the pH near 6.0 to make copper easily diffusible to the roots.
- How to prevent: Avoid over-applying phosphorus, which hinders the absorption of copper.
Molybdenum
While used in tiny amounts, molybdenum mediates the absorption of nitrates used in building plant proteins.
- Symptoms: Weed leaf deficiency symptoms of molybdenum often start at the young leaf margins. The margins can appear distorted, chlorotic, or dried.
- Toxicity: Produces iron-like deficiency symptoms if there is an excess molybdenum since iron is locked-out.
- How to treat: Use foliar sprays containing diluted concentrations to avoid toxicity.
- How to prevent: Focus on adjusting the pH to the optimal range.
What Are the Most Common Marijuana Plant Deficiencies?
Weed plants deficiencies vary depending on the soil type and method of cultivation. Usually, the lack of micronutrients like iron and magnesium deficiencies results from the overapplication of the macros. For instance, elevated concentrations of phosphorus and potassium in the soil can lead to the nutrient lockout of less potent elements, such as iron and magnesium. Meanwhile, the soil pH can also influence the nutrient plant deficiencies; so it might be challenging for a beginner to successfully locate and eradicate the issue. No worries, this is why we're here to help!
The names of the nutrients are not just vague memories from chemistry classes at school, they are building blocks that your plant uses to grow. Fortunately, with this guide at hand, you can now call yourself a proud plant parent and a smart plant dietologist. Time to help your cannabis eat healthy!
FAQ
What Are 3 Symptoms a Plant Could Use to Show You They Have a Nutrient Deficiency?
Depending on the weed nutrient deficiency, the symptoms can vary. However, the most common signs are the general yellowing of the younger leaves, purpling or bronzing, and the uneven yellowing of the leaves.
What Is Deficient in Cannabis During Flowering?
Potassium deficiencies are often linked to the burnt appearance of the leaves, typically starting on the older ones during the flowering stage. This is because growing buds demand higher concentrations as they increase in size.
Can Cannabis Recover from Nutrient Deficiency?
If you notice nutrient deficiency early, your greenie has a high chance of quickly getting better. Unfortunately, late-stage symptoms such as deformities and necrosis (death of leaf tissue) usually signal irreversible injuries that cannot be repaired by simply supplementing nutrients to the plant.
What Is a Nutrient Burn?
A nutrient burn is characterized by partial or complete leaf necrosis as a result of fertilizer overapplication. Although various chemical processes influence the symptom appearance, it is often associated with the toxicity of the overapplied elements or the salt concentrations in the roots.
When Do Nutrient Deficiencies Typically Occur in Cannabis Plants?
Nutrient deficiencies can occur anytime during the growing season. For instance, nitrogen and sulfur deficient plants manifest symptoms at vegetative stage, while potassium deficiency may only become evident during the bud formation.
