7 Must-Have Nutrients for Growing Weed
Article written by
Homegrown Cannabis Co.American Seed Bank and Cultivation Experts
Content reviewed by
Dr. Lewis JasseyMedical Director - Pediatric Medicine
Are you preparing to mix up or buy the best nutrients for growing weed? You need NPK and an assortment of secondary minerals in varying quantities. NPK stands for nitrogen (N), phosphorus (P), and potassium (K).
Natural environments contain all minerals necessary for plant growth. Relying solely on the soil doesn’t leave you with the highest possible quantity of sticky buds, though. Hydro and aeroponic cultivators have complete control and, therefore, responsibility over feeding. As a result, understanding cannabis nutrients is key to cultivation success.
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Why Nutrients Matter
Cannabis plants need food to fuel development. These minerals help the foliage develop, roots to stretch, and buds to become big and sticky.
Essential nutrients for cannabis cultivation are nitrogen, phosphorus, and potassium (NPK). These three are macronutrients, meaning plants need them in large quantities. We also have secondary minerals and trace elements (micronutrients).
Secondary minerals are calcium, magnesium, and sulfur. They’re necessary for healthy plants but in much smaller quantities than NPK. Micronutrients aren’t the primary marijuana food, but they support various life processes.
As a grower, you meet this need by using fertilizers. Feeding weed is one of the cultivation essentials to master.
You can make marijuana nutrients from organic matter at home or buy them in a gardening store. In the latter case, consider the following specifications of available products:
- NPK ratio: Plants need varying quantities of NPK in different stages of development. Brands vary in what they consider optimal, and you should rely only on reputable ones.
- Ingredients: Some manufacturers use all-natural sources, while others employ chemicals. The former suits organic soil and hydroponic cultivation; the latter is perfect for hydroponic and aeroponic setups.
- Optimal setup: Soil and hydroponic systems require varying amounts and compositions of minerals.
Sellers might also offer supplements on top of regular fertilizer. These contain low NPK amounts, focusing on micronutrients to help resolve deficiencies and boost growth.
What Do Nutrients Do?
We mentioned three categories of nutrients (macronutrients, secondary minerals, and trace elements) for growing marijuana. Here’s what they do:
- Nitrogen is primarily responsible for vegetative growth. It enables photosynthesis and creates amino acids, acting as a building block of branches, leaves, and buds.
- Potassium lets the plant acquire carbon dioxide for photosynthesis. It also strengthens the root system and makes marijuana more resilient to droughts. As such, it’s necessary throughout the life cycle (but more in blooming).
- Phosphorus is essential for the flowering phase. It supports energy storage, utilization, and flower formation, making buds big and resinous.
- Calcium strengthens plant cells and helps marijuana absorb other minerals.
- Magnesium supports photosynthesis and protein synthesis, making plants grow strong and sturdy.
- Sulfur boosts plant resistance to diseases and aids chlorophyll production.
- Manganese supports photosynthesis and enables the absorption of other minerals.
- Boron helps build the plant wall, strengthening the stem, branches, and stalks.
- Iron helps energy storage and utilization. It’s also a bud booster, making weed flowers thick and round.
- Zinc supports chlorophyll production, photosynthesis, and healthy green vibrancy in weed plants.
- Copper makes plants disease-resistant and supports seed production.
- Molybdenum optimizes how plants absorb other nutrients, especially nitrogen.
7 Must-Have Nutrients for Growing Weed
Cannabis growers don’t have to be chemistry experts and supply each nutrient in isolation. Fertilizers are concentrated sources of essential nutrients: pick the right one, and feeding becomes easy. Below are seven excellent options.
1. Super Soil
Super soil is an organic growing medium that contains all the minerals marijuana needs to survive and thrive. As such, it abolishes the need for weekly feedings.
You might buy blends with the best nutrients for cannabis, but they’re rather expensive. You can also mix them yourself. It’s a straightforward process of adding worm castings, blood meal, bat guano, dolomite lime, and Epsom salts in regular soil.
2. Soluble Fertilizer
Soluble fertilizer is the most efficient and straightforward way to feed cannabis plants. These powders contain the right nutrients for each growth stage: all you need to do is follow the manufacturer’s instructions.
Choose your nutrient companies right to ensure success with this alternative. We recommend that you shop with a reputable seller like Homegrown Cannabis Co. They offer synthetic and organic fertilizers for optimal plant development.
3. Bone Meal
Bone meal is an organic nutrient blend of ground slaughterhouse waste products and animal bones. It’s a fantastic source of phosphorus, calcium, and secondary nutrients for plants in the vegetative and flowering stages.
This blend offers a slow nutrient release, so the risk of nutrient burn is minimal. If looking to resolve a deficiency, blood meal acts more quickly.
4. Manure
Manure is an organic fertilizer that mainly consists of animal feces. It’s an excellent bud booster, rich in nitrogen, potassium, phosphorus, copper, manganese, and zinc.
You can get hot and cold manure. The former is rich in moisture and quick to decompose, offering a quick nutrient infusion. The latter is slower to release minerals, feeding your plants across an extended period.
Most manure sources have similar nutrient compositions. If striving for accuracy, choose horse feces for vegging and cow feces for flowering.
5. Compost
Compost is an organic blend of decomposed plant materials, food waste, and manure. Mixes of coffee grounds, kelp, and green waste are rich in nitrogen; those with feces supply phosphorus.
Composting provides a constant source of nutrients, reducing the risk of deficiencies. It’s also gentle enough not to burn plants.
6. Bat Guano
Bat guano consists of bat droppings and contains plenty of nitrogen, phosphorus, and potassium. It’s not rich enough to be the primary source, but it can support plants in vegging and flowering while promoting a rich microbial life.
7. Alfalfa Meal
Alfalfa meal is an organic plant booster made of ground-up alfalfa plants. It’s a fantastic soil amendment for replacing lost nitrogen between growing seasons. It also kickstarts vegetative development and supplies secondary nutrients: calcium, sulfur, magnesium, iron, copper, zinc, and boron.
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How to Identify Nutrient Deficiencies
Nutrient deficiencies harm marijuana plants and reduce the harvest potential. Symptoms vary with the mineral and growth stage. Since they often overlap, we list common warning signs and their potential reasons below.
Stunted Growth
Cannabis needs ample light and nutrients for healthy growth. When there’s an NPK shortage, they become slow to stretch and fatten. A lack of calcium or sulfur may also trigger this issue, leaving you with new leaves and stems that lack vibrancy and vitality.
Here’s how to differentiate between these three:
- A lack of NPK introduces overall discoloration and drooping.
- Calcium deficiency makes young leaves and shoots yellow and purple.
- Mid-section foliage pales first due to a sulfur deficiency. The leaves also become narrow.
Discolored Leaves
Yellowing leaves on weed plants are among the leading deficiency symptoms, and nitrogen, calcium, magnesium, and iron shortages are responsible.
Since nitrogen is mobile and the others aren’t, the location of this symptom can tell you what you’re dealing with:
- Yellowing progresses upward: When there’s a nitrogen deficiency, plants prioritize new growth. The mineral travels up from the base, and older leaves are the first to appear pale and lifeless.
- Yellowing progresses downward: Calcium, magnesium, and iron don’t move upward. When they’re in shortage, young blades are pale and yellow, while the old ones retain greenery.
Potassium and zinc deficiencies may also cause discoloration. The blade becomes pale in this case, and the veins remain green for some time longer.
Curled Leaves
Leaf edges curling inward often point to nutrient toxicities, but they also happen due to potassium or molybdenum deficiency. Here’s how to differentiate between these two:
- Potassium shortages emerge as discolored leaves, stunted growth, and dying foliage. They’re more common than the alternative option.
- Molybdenum shortages cause curling, clawing, and crimson coloration on leaf tips.
Spotted Leaves
Spotting is a dangerous deficiency symptom. Brown, rusty, and yellow dots appear on the blade and eventually spread, making the entire leaf die. A lack of potassium, calcium, magnesium, or boron can trigger it.
- A potassium deficiency is an all-around problem, causing discoloration, spotting, foliage death, and stunted growth.
- A calcium deficiency halts growth and stunts the root zone. Young shoots are tiny, deformed, and pale.
- A magnesium deficiency makes plants appear weak, limp, pale, and sickly in the vegetative phase.
- A boron deficiency causes burnt and brown leaf tips and dead spots across the blade.
Burnt Leaf Tips
Burnt tips often point to excessive amounts of nutrients. They also appear due to potassium, boron, and copper deficiencies.
- A potassium deficiency hits the entire leaf, stem, and flowers. Growth halts, the plant loses color, and leaves die and become spotted.
- A boron deficiency causes dead spots on the blade and red or brown tips.
- A copper deficiency attacks the leaf tips, making them gray or blue.
Brittle Stems
A lack of nutrients for cannabis weakens the stem and branches. As they progress, many deficiencies cause this symptom. It happens early in nitrogen and silicon shortages.
- A nitrogen deficiency slows down growth and makes old foliage weak and pale. Leaf stems are fragile and brittle, too.
- A silicon deficiency is near-impossible outdoors but happens with inadequate hydroponic nutrients. A lack of this mineral makes photosynthesis impossible and weakens plants.
Color Changes
Discoloration is more frequent than other color changes, but some deficiencies make the stem and leaves turn blue, red, and purple.
- Red and purple stems are telltale signs of a magnesium deficiency.
- Blue and purple stalks point to a phosphorus deficiency.
- Blue leaf tips suggest a copper deficiency.
Resolving Deficiencies
Once you diagnose a nutrient deficiency, it’s time to resolve it. Don’t rush to supply fertilizer or added nutrients, though. Due to secondary reasons, your plants are likely not absorbing the available minerals.
Inadequate pH levels in the growing medium are the leading cause of deficiencies. Cannabis can only consume food in a slightly acidic setting (6.0-7.0 in soil, 5.5-6.5 in hydro). To start, test your medium and see if there’s an imbalance.
If there is, flush the soil or reservoir with pH-neutral water before supplying new minerals. Regularly test your water source, nutrients, and runoff to catch future trouble.
Once you fix the issue, removing all affected branches and foliage is a good idea. Otherwise, they might rot, die, and spread pathogens to healthy growth.
Tip: The necessary amount of minerals depends on the medium. If using hydroponics or coco coir, you might need to supply additional calcium and magnesium. Research your soil type or system to prevent potential hazards.
The Bottom Line
Getting the nutrients right is among the critical factors of successfully growing cannabis. Get the best genetics, water generously, provide plenty of light, and feed well to get top-tier buds.
As a soil cultivator, NPK is your primary concern. Hydroponic growers should acquire fertilizers with macro and micronutrients. In either case, learn the signs of deficiencies and act quickly to get your garden back on track if anything goes wrong.
This guide outlined the basics of feeding weed, so why not put the theory into practice? Visit our partner Homegrown Cannabis Co. to buy high-quality seeds and fertilizers to grow like a pro.
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Frequently Asked Questions
What nutrients do seedlings need?
Seedlings don’t demand fertilization during the first week of their life. The nutrient stores found in cannabis seeds are enough to sustain this initial growth. They require moderate amounts of nitrogen, phosphorus, and potassium (usually a 2-5-2 ratio) once they reach three inches tall.
What nutrients do vegetative plants need?
The feeding schedule in the vegetative stage should focus on nitrogen and contain smaller amounts of phosphorus and potassium. The ratio in most fertilizers is 9-1-7.
Other essential nutrients for vegging include calcium, sulfur, magnesium, and trace minerals. Most soils contain ample quantities of these, so only supplement if you notice a deficiency. You should provide them all manually in hydroponic systems.
What nutrients do weed plants need during the flowering stage?
The flowering stage requires gradually increasing phosphorus and potassium concentrations while reducing nitrogen. The optimal ratio is 6-2-12. Cannabis still needs all micronutrients in small quantities, too.
Feed once a week and stop ten days before you harvest. That way, plants use their nutrient stores, and your buds have no harsh chemical flavor.