Macronutrients vs. Micronutrients in Cannabis: What Each One Does

Macronutrients are the elements a cannabis plant needs in large amounts (nitrogen, phosphorus and potassium), while micronutrients are the ones it needs in tiny doses, like iron, zinc, boron and manganese. Your plant needs both at every stage of growth, and if you want killer buds, neither can run short.

What are macronutrients?

Macronutrients are essential to a plant's overall health, and it needs them in large quantities. Think of them as the plant version of the protein, fat and carbs we need to survive.

So which ones are they? There are three primary macronutrients: nitrogen (N), phosphorus (P) and potassium (K). How much of each your plant needs (the NPK ratio) shifts depending on the stage of the grow.

What is NPK? On a fertilizer label, NPK refers to the main macronutrients involved in plant nutrition: nitrogen (N), phosphorus (P) and potassium (K). Together they go by the acronym NPK.

In the vegetative stage, for example, plants need more N and less P and K. Once your weed hits the flowering stage, it needs a lot less N and more P and K.

To give your plant these elements, you can go with natural organic nutrient sources or use commercial fertilizers (some of which are also organic) from your local grow shop.

Nitrogen (N): fuel for leaves, stems and branches

Among plant nutrients, nitrogen is one of the most abundant elements on the planet. It's a core component of chlorophyll and it's constantly on the move inside the plant. It handles several jobs at once: it keeps photosynthesis running and it's a building block of the amino acids that go on to form proteins.

Cannabis plants use nitrogen mainly to build stems, branches and leaves. Bloom nutrients push the plant to stop putting out new leaves and branches and focus on growing flowers, using mostly phosphorus and potassium.

Nitrogen goes into making chlorophyll. Without nitrogen, plants can't make the food they need, and they won't have what it takes to grow. Without enough chlorophyll, the plant can't photosynthesize and will eventually start to wilt.

Watch out for overwatering and extreme temperatures, because both can make your plants lose nitrogen. On the flip side, too much nitrogen will turn your plant dark green and can delay flowering, so it keeps pumping out leaves instead of calyxes.

If you're using bottled fertilizers, go easy when you water them in. Don't overdo it, because you can burn the roots beyond repair.

If you're going organic, pay attention to what goes into your compost, like ferments, leachates and other natural inputs.

Phosphorus (P): roots and flowers

Phosphorus is another macronutrient that's essential for life. Phosphates are part of the DNA and RNA of every living thing, and phosphorus binds strongly and stubbornly to soil, so it doesn't wash out easily when you water.

Among cannabis nutrients, this one is key for photosynthesis and root development. In flower, you ramp up phosphorus along with potassium after cutting back on nitrogen.

A phosphorus deficiency can mess with the plant's ability to absorb other essential nutrients and can seriously hurt your cannabis plant's health, disease resistance, bud quality and final yield.

One more heads-up about phosphorus in particular: be careful with bottled PK boosters. More food isn't always better, and instead of fattening up your buds you might end up with an overdose you can't undo this late in the cycle.

Potassium (K): bud weight and water balance

Potassium is one of the most important nutrients for weed plants and it's involved in synthesizing proteins and amino acids from nitrogen in its ammonium form, so the interaction between these two nutrients is vital for a bunch of the plant's metabolic processes.

It's an alkali metal your cannabis plant can't do without. Potassium plays a starring role in flowering, and running short on it can make a real difference in your final harvest. Its big jobs: helping your buds fatten up, regulating salt levels in the plant and opening and closing the stomata on the leaves, the tiny pores that handle CO2 intake.

When a cannabis plant is short on potassium, it shows visible symptoms like leaf discoloration. The leaves yellow from the tips toward the center, ending at the base of the leaf. You'll also notice the stem gets weak and bends easily.

What are micronutrients?

Plants also need a fairly long list of micronutrients to stay healthy, productive and disease-free. They only need them in small amounts, but running short can cause serious problems.

Micronutrients are a lot like vitamins for us: we don't need huge amounts, but our health takes a hit when we don't get them.

Which micronutrients does a plant need? Beyond the secondary nutrients calcium, magnesium and sulfur, the main ones are iron, manganese, boron, zinc, copper and molybdenum. They're in most, if not all, fertilizers, but usually in much smaller amounts than the primary macronutrients.

What do micronutrients do? They're essential for a plant to develop and function properly. Your cannabis plant relies on a whole roster of these trace elements to build the strength it needs to hold up heavy flowers.

Micronutrient deficiencies aren't very common, but when they do happen they can hurt your plant's health, growth and yield.

Boron: stronger cell walls

Boron helps reinforce cell walls. It has a major structural role: about 90% of it goes into cross-linking the large carbohydrate molecules that make up cell walls.

If your plants have a boron deficiency, their structure can suffer.

Copper: photosynthesis and metabolism

Copper is one of the soil micronutrients that also pitches in on photosynthesis. This fairly immobile nutrient helps plants metabolize carbohydrates and proteins.

Iron: healthy chloroplasts

Iron is one of the micronutrients that really matters: it helps plants maintain the structure and function of their chloroplasts, the organelles that turn light energy into sugars the plant's cells can use.

Understanding what micronutrients bring to the table, especially iron, is key, because iron is a major component of a huge number of enzymes and pigments.

Manganese: nitrogen use, respiration and pollen

Manganese contributes to some of the most important systems and functions in cannabis plants, including nitrogen assimilation, respiration and photosynthesis.

Like other weed nutrients, it also plays an important role in reproduction, helping pollen tubes develop and pollen germinate.

Molybdenum: turning nitrate into amino acids

Molybdenum plays a key role in two enzymes that let plants synthesize amino acids. One helps convert nitrate into nitrite, while the other converts nitrite into ammonia.

The cool thing is that plants can easily move this mobile nutrient to wherever it's needed most.

Zinc: growth hormones and internodes

Zinc influences a lot of plant processes, even in tiny doses. This immobile nutrient is part of several enzymes and proteins, and it helps produce growth hormones and develop the internodes (the stretch of stem between nodes).

Both macronutrients and micronutrients are a must when you grow cannabis. They're vital for healthy plant development. That said, how you feed will vary depending, of course, on the growing medium you use.

One more thing: the best advice when feeding is to start with half the dose recommended on the fertilizer label, and work your way up as long as your plant isn't showing signs of overfeeding.

Investing in good nutrients is always worth it, in our book. Just stick to trusted brands with solid reviews from other growers. Finally, it's crucial to watch for changes in the leaves and the whole plant so you know whether you're feeding your grow right.

Overdoing nutrients is dangerous for your plants because it can lock out elements like calcium, magnesium, zinc and iron. If that happens, you can flush the roots with at least three times as much water as the container holds to wash out the excess nutrients.

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