Best Nutrients for Vegetative & Flowering Marijuana Growth Phases

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Like all other plants, marijuana needs nutrients to grow bigger and bear flowers. However, you can’t just casually give fertilizer to your cannabis plants and expect a nice yield. More is not always better, you need to know the exact amount to give to your plant and usually, it takes experience to get it right.     

That doesn’t mean that you’re out of luck if you’re a beginner. If you’re totally clueless about where to start with nutrients for your marijuana plants, read on. 

The kind of nutrients your plants need

A bag of NPK fertilizer

Like most plants, cannabis also requires a particular set of elements called macronutrients and micronutrients. As you might have guessed, plants require macronutrients in larger amounts and micronutrients in trace amounts only. 

Macronutrients

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Calcium
  • Magnesium
  • Sulfur
  • Carbon
  • Hydrogen
  • Oxygen

Micronutrients

  • Zinc
  • Iron
  • Manganese
  • Molybdenum
  • Chlorine
  • Cobalt
  • Silicon
  • Boron
  • Copper

Plants get these mineral and non-mineral nutrients from the soil or planting medium, in water and air. Normal soil often has a lack or imbalance of these nutrients which is why growers prefer to use organic potting soil or add fertilizer to normal soil. Some even do away with soil altogether and instead use another planting medium like nutrient rich water like in the case of hydroponics.    

Is organic better?

Just like most people who prefer organic produce, lots of marijuana users say that they have a better experience with organic weed. So what exactly is the difference between organic and non-organic in the context of weed growing?

When growers talk about organic soil and fertilizer, they are referring to products made out of decomposed plant and animal material instead of straight-up chemicals. Ingredients in organic potting soil and fertilizers usually include the following: 

  • Compost
  • Mulch 
  • Manure – Guano (bat droppings), worm castings, etc.
  • Bone, soybean, fish or blood meal
  • Soft rock phosphate
  • Seaweed
  • Greensand

Organic soil and fertilizers allow your cannabis plant to grow in its natural setting where it can use up nutrients at its own pace. However, there can also be a presence of microbes and bacteria that impact the plant’s health. 

Hydroponics

Non-organic growing mediums like hydroponics and inorganic fertilizers like NPK (nitrogen, potassium, phosphorus) also have their own advantages and disadvantages. Giving your plant the exact amount of inorganic fertilizers can trigger explosive growth but if you get it wrong, you can end up overfeeding your plant. In fact, the incorrect amount of fertilizer can give your plant “nutrient burn” where its leaves can shrivel up and look dried up. 

Most home growers often get the best results using fully organic soil and fertilizers while supplementing with a very small amount of inorganic fertilizer whenever needed. Meanwhile, commercial cannabis farmers often prefer hydroponic setups since it gives them a number of advantages like bigger yields despite using less water, space and nutrients.   

Nutrient requirements at each marijuana growing stages

I’m sure that you are already aware that the cannabis plant, whether autoflower or photoperiod, will undergo two stages of growth after its seedling phase. The vegetative stage is when the plant uses all its energy and resources to grow while the flowering stage, as its name suggests, is when the plant focuses on growing buds. Each stage has a different nutrient requirement.

It’s a good time to be a home grower nowadays since you don’t even have to pore over stuff like what kind of fertilizer to give your plant when and how much. Companies like Fox Farm offer fertilizer packages like the Liquid Nutrient Trio Soil Formula that are specially formulated to give the right balance of nutrients per growth stage and even provide a feeding schedule on their website. With this, all you need to do is follow the feeding schedule and use the right bot tle on your plant, no more guesswork involved!

If you’re growing to get some nice buds, then you’ve probably also invested in good potting soil. Potting soil like Fox Farm’s Ocean Forest are already considered “hot”, meaning it’s already loaded with nutrients which can be too much for young seedlings. But if your seedlings or cuttings are showing signs of nutrient deficiency, you may need to gradually introduce a 1-1-1 balanced formula at about 100 ppm for each once the roots have developed a bit.

Vegetative

Nutrients typically required:

  • Nitrogen
  • Phosphorous
  • Potassium

Your plants will definitely start to eat up a lot of nutrients once it hits the vegetative stage. This stage lasts around 4 weeks to even 2 months, depending on the plant’s strain and growing conditions. You generally would want to increase feed rates up to about 200 ppm for nitrogen, 120 ppm phosphorus and 200-250 ppm for potassium. But generally, you would not need to bother with individual nutrients if you’re using a fertilizer pack that includes a growth formula like General Hydroponics’ FloraGro, just follow the instructions and apply. 

Here are some other popular fertilizer products:

Flowering

FoxFarm Water Soluble Plant Foods, Pack of Three 1lb Canisters

Nutrients typically required:

  • Nitrogen
  • Phosphorous
  • Potassium
  • Boron
  • Calcium
  • Magnesium

Adding nutrients during the flowering stage is a little bit more complicated. Experienced growers already know the process so well that they are able to fine-tune the feeding ratio even further into sub-stages. 

Once your plant enters the flowering stage, you’ll need to introduce a bit of calcium and magnesium which helps improve your plant’s root system. At this point, start reducing nitrogen then shift to around 200-250 ppm NPK at the start of bloom with a bit of boron in the feed program. 

During the late stages of the flowering period, you can reduce the nitrogen even further to around 125 ppm. Make sure that you apply adequate amounts of phosphorus once you can see the calyx or sepals forming. A ratio of 1 to 1.5 of N to K in the last four weeks of bloom is recommended. You can also consider some potassium silicate to help strengthen your plants until flushing. 

Then again, if you don’t want the headache of micromanaging your plants’ nutrients during this stage, you can just pick up a bottle of “bloom” fertilizer. Here are some popular examples:

How to feed nutrients to your cannabis plants

If you’re running a hydroponic setup, it’s likely that you already have a decent amount of experience using “nutes”. If you’re a beginner who’s using soil as a medium, getting the right balance of nutrients all the time can be a challenge. Aside from dealing with the changing nutrient requirements of your plants as they transition from one stage to another, here are few other things that cause a nutrient imbalance in your soil that you need to keep in mind:

  • Micronutrient lockout – this is when some nutrients react with others and become unusable.
  • Plant waste – as your plant consumes the nutrients in the soil, it will generate byproducts that will contribute to the nutrient imbalance of the soil.
  • Soil pH imbalance – chemical reactions needed for nutrient uptake can be inhibited by improper soil pH.

As you can see, using fertilizer on soil can be a bit trickier which is why it is a good idea to always check the nutrient and pH level of your soil.

When using most brands of fertilizer, you want to start at 25% strength, despite what the label might say. It’s easier to start low then increase from there than to burn your plants on the first try. In almost all cases, diluting your chosen brand of fertilizer with water to 1/4 strength is usually enough for indoor homegrown plants. Never ever put the fertilizer directly into the soil!

Of course, not all plants are the same. Bigger plants will naturally use up more nutes and some strains are known to require more than others. If you notice that your plant is looking a little yellow and not a lush green, try going up to 33% strength first then observe for a week. At first you have no choice but to figure out by trial and error what concentration of your chosen fertilizer works best but as you grow the same strains over and over, you’ll start to have a good feel for it.

Nutrient Brands to Consider

While fertilizer blends and packages make life easy for new growers nowadays, the sheer number of brands and products to choose from can be confusing. To help you out, we’ve made a list of some of the most popular fertilizer brands that frequently get good reviews from the cannabis community.

Frequently Asked Questions

Is soil good enough for growing marijuana plants?

Soil is a good growing medium for beginners since it is easier to manage than a hydroponic setup. However, you should use good potting soil instead of regular garden soil if you want your plants to grow well.

Do I need to give nutrients to marijuana plants?

Yes, if you want to increase your yield. Although your cannabis plant will grow fine with just light and water, what you want is to maximize the time and effort you spend on taking care of your plants. Using fertilizer will tremendously improve the quality of your buds and quantity of your harvest.

Why do I need to add nutrients for cannabis plants?

Cannabis plants can use up a lot of nutrients and they can even deplete hot potting soil in a few weeks as they grow. For hydroponic setups, you cannot do without nutrients since water is basically your medium.

What is the best fertilizer for my cannabis plant?

This depends on what kind of growing setup you have. For most home growers that are using soil as a growing medium, the best would be “grow and bloom” fertilizer packs like Fox Farm’s Liquid Nutrient Trio.

Which is better for my marijuana plant, organic or inorganic fertilizer?

Both methods has its advantages and disadvantages. For home growing purposes, organic fertilizers are typically more advantageous as they won’t damage the plant as much if you don’t apply them correctly.

Conclusion

Feeding your cannabis plant throughout its life cycle is a detail-oriented task, that is, if you want to harvest buds that you would be proud of. Thankfully enough, there’s now a plethora of choices when it comes to a complete plant food solution that would take you from start to finish of your marijuana plant’s life. These fertilizer products eliminate the guesswork out of plant feeding so that you can achieve a harvest of buds that can rival those sold at dispensaries. Although these fertilizers will provide all the steps that you need to do, it would be good to understand the nutritional requirements of your cannabis plant so that you can adjust whenever the situation calls for it. 

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