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How Often To Fertilize in Flowering Stage: Things To Know

By Last updated on May 9, 2024Last updated on May 9, 2024No Comments

You’ve been taking care of your cannabis plant for weeks now. Finally, you start seeing blooms. Oh, the sheer joy of that!

But the appearance of blooms is not a sign for you to get lax. Instead, you need to make sure your plants are getting the proper nutrients and environment for the flowering stage.

The common question most growers have is: how often should I fertilize my plant? Let’s find out.

An Overview of the Flowering Stage

An Overview of the Flowering Stage

Just because your buddy’s plants flowered after eight weeks doesn’t mean yours would too. The process can take anywhere up to 11 weeks.

How soon your cannabis plants flower will depend on a few conditions. For one, where are you growing the plant? If your plant pots are outside, they will be influenced by the changes in outdoor temperature and sunlight. Such plants flower at the end of summer when the days are short.

But when you grow your plants indoors, you can control the flowering stage. Many growers let their plants stay in a vegetative state for about four weeks and then move them toward flowering. But you can take your time.

The key is to reduce light exposure. When weed plants get less light, they stop making foliage. Instead, they use up their nutrients to grow buds.

But lighting is not the only factor that impacts the flowering stage. Nutrients also have an equal role to play.

How Often Should You Fertilize Cannabis Plants in the Flowering Stage?

Ideally, you should fertilize your cannabis plants once or twice per week in the flowering stage. But don’t simply throw in as much fertilizer as you want.

Most growers follow a 5-20-5 NPK ratio. Not familiar with NPK? Let us quickly explain.

The ‘N’ is for nitrogen, ‘P’ is for phosphorus, and ‘K’ is for potassium. The NPK ratio shows the concentrations in which these nutrients are present in a fertilizer mix.

Here’s what a 5-20-5 ratio means: 

  • Five parts nitrogen 
  • 20 parts phosphorus 
  • Five parts potassium 

Some growers also put in a 5-25-10 NPK ratio during the flowering stage. Notice the pattern here. The concentration of phosphorus has to be the highest because it promotes bud growth.

You don’t want to add in a lot of nitrogen because it would boost growth. That requires a lot of energy that the plant can otherwise use to create buds.

But you want the plant to develop buds rather than leaves or stems. Meanwhile, potassium concentration should also be high as it makes the roots stronger.

When buying fertilizer for your cannabis plants’ flowering stage, opt for specialized varieties. These cannabis-blooming fertilizers have pre-determined ratios. So, you don’t need to do any math yourself.

If you think your plant needs some extra boost, add secondary nutrients to the mix, like iron and magnesium.

Secondary Nutrients for Cannabis Flowering

These nutrients can help your plant grow bigger buds during the flowering stage:

  • Sulfur: Lets cannabis plants absorb water and other nutrients
  • Calcium: Allows the plant to absorb nitrogen from the soil
  • Magnesium: Allows light absorption for better bud productions
  • Iron and Manganese: Help the plant produce chlorophyll, the green pigment which helps the plants convert light to energy
  • Copper: Strengthens stems and branches

You don’t necessarily need a lot of nutrients for your weed plants during the flowering stage. But it might help to add them, especially if you think your plant needs an extra push.

Fertilizing Cannabis Flowers from Week 6 to 8

Weeks 6 and 7 mark the end of the blooming stages. So, it’s time for you to get ready for harvest.

At this point, the cannabis plant buds must be firm and dense. They should also have a thick trichome layer, most of which should be milky white. By Week 6, some trichomes turn amber too.

In the next week or so, the pistils will become even darker. You can check this out using a magnifying glass or a pocket scope.

Calcium, potassium, and phosphorus are important nutrients for the plant in these stages. Make sure to use fertilizers that are specifically designed for the flowering stage.

Once most of the trichomes turn milky white, it’s time for harvest. Cannabis plants harvested early have a euphoric and uplifting effect. Meanwhile, if you wait for a week or two, your plant will have a more ‘sleepy’ effect.

When to Use Enzymes

Enzymes are proteins that speed up several biochemical reactions in cannabis plants. They can help your plant decompose soil organic material to maintain a nutritional balance.

Most growers use enzymes throughout the cannabis growing process. But they are especially helpful during flowering stages because the plant has high nutritional needs during this time.

You can easily find cannabis enzymes in the market. Go over to your local garden store and ask for one.

When to Stop Fertilizing Cannabis Plants?

Weed is a hardy plant. That means it doesn’t require too many nutrients at all times. So, when do you stop fertilizing your cannabis plants?

There’s some debate about that, but most growers believe you should limit fertilizing three weeks before you harvest the plants. Stop fertilizing completely two weeks before time.

After that, simply water your plants to ‘flush’ out the excess fertilizers. Flushing is a process where you water your plants to get rid of the extra salts and minerals that may have built up over time.

If water alone doesn’t do the trick, you can use cannabis root cleaners. These help absorb any remaining minerals from the soil, flushing them out from the substrate and cannabis roots.


The cannabis plant doesn’t have excessive fertilizing needs. But once it enters the flowering stage, it requires certain nutrients to develop stronger buds and make flavorful flowers.

That’s where nitrogen, potassium, and phosphorus come in. The latter is more necessary for the plant compared to nitrogen. You can also supplement your plant with secondary nutrients like manganese, iron, magnesium, and sulfur.

The simplest way to ensure your plant gets the nutrients it needs is to buy a premade weed fertilizer. Choose one that focuses on the flowering stage.

The Sanctuary Editorial Team

Our writers use a combination of research and personal experiences to eloquently tackle these topics. The research process utilizes multiple levels of information. We reference informal channels for details relating to casual topics such as describing slang or how to create a bong out of fruit. We also examine scientific publishings for up-to-date research. The accuracy of our articles is crucially important to us and they are written with the idea of inclusiveness for readers of all walks of life.