When To Switch To Flowering Nutrients (Avoid This Mistake)

The right time to switch to flowering nutrients depends on whether you are growing from seed or a clone, as advice is a little different for each method.

If You’re growing from seed…

If you are growing cannabis from seed, then there are three different ways you can tell that they are ready for flowering nutrients.

1. First signs of sexual maturity

The easiest way to tell when it’s time to switch to flowering nutrients is to inspect your plants for signs of sexual maturity. Sexual maturity begins when the first set of pistils appears. If you are seeing little white hairs (pistils) on your plant, your plant is sexually mature and ready to flower.

The first signs of sexual maturity is the ideal time to start giving early bloom nutrients to most cannabis plants.

Consider the image below. Looking closely, you can see long, wispy white hairs protruding from the nodes. This means the plant is sexually mature, and now is the perfect time to switch to flowering fertilizers. 


Can you see the white pistils? They are beginning to become many, and this is a sure sign that your plant is ready to switch to early bloom nutrients.

Here is another way to tell your plant is ready for flowering nutrients:

2. Your Plant Has Begun the Pre-Flower Stretch

If you really want to push your plants for optimal production, you can apply flowering fertilizers even before the pistils appear. You can switch to flowering nutrients as soon as your plant begins the pre-flower stretch phase.

If your plant has begun the pre-flower stretch or ‘flowering stretch,’ your plant has switched gears from childhood to adulthood. In human terms, a plant that has begun the pre-flower stretch is leaving its childhood and becoming a young adult. 

The pre-flower stretch may last from 1-3 weeks. You will likely notice the stretch has begun just two or three days into the stretch before pistils appear. 

Once you notice unprecedented, rapid, vertical growth each day for two or three consecutive days, you can give your plants their first flowering food, as they will soon show sex. Remember, be conservative when first switching to a flowering fertilizer. Less is more.

Consider the following image as an example:

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This plant began the pre-flower stretch less than a week before this photo was taken. Now is a great time to use early bloom nutrients if you want to push your plant for maximum flower production.

Your Plant is a Long Veg Plant

Veg plants rely heavily on nitrogen fertilizers with minuscule phosphorus and potassium (P & K). Conversely, flowering nutrients usually consist of reduced nitrogen (N) and increased (P) & (K). In theory, you should not give your veg plants flowering nutrients. 

However, if a cannabis plant is kept in the veg phase for three months or more, it will likely become deficient in (P) & (K). A marijuana plant in a prolonged veg period will likely require flowering nutrients before being sexually mature.  

One dose of flowering nutrients to a long-cycle veg plant should fix the problem if deficiencies arise. Don’t forget to add your micronutrients to your flowering nutrients for long veg period plants. 

Only use flowering nutrients on veg plants as needed.

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This plant is approximately 100 days old and has never left veg. A (K) deficiency developed mid-canopy (canopy is trained flat). Flowering nutrients were applied, and the new growth is healthy and green.

When to Switch from Early Bloom Fertilizers to Late Bloom Fertilizers

Once a plant has visibly stopped stretching, it focuses its remaining energy on fattening its buds. Vertical growth stops, and it’s the sweet spot for switching from early bloom to late bloom fertilizers.

Your Plant Started as a Clone… 

You can give your rooted and transplanted clones bloom food as soon as you place them in a flowering light cycle. 

Clones begin to flower almost immediately after exposure to a flowering light cycle and can immediately benefit from flowering nutrients. 

It seems simple, but the right time to feed clones bloom fertilizers depends on the purpose of cloning and the stage of growth the clones are currently in. 

Clones that go into the veg room do not need flowering fertilizers. Only when the clones go into the flowering room, and they have roots, should they receive bloom nutrients. 

Additional Tips on Flowering Fertilizers for Clones: 

  1. Allow your plants to recover a few days before being transplanted before applying flowering nutrients. The shock of transplant combined with the shock of new nutrients can harm your plants.
  2. NEVER apply flowering nutrients (or any nutrients) to a cutting that has not yet rooted. If so, you will burn your cuttings, and they will wither.
  3. Don’t give your plants flowering fertilizers before transplanting them. Wait until the plant has recovered from the transplant, and then give them flowering nutrients. The additional stress can stunt your plants or worse. 

When to Use Flowering Fertilizers in a SOG

Many gardeners place their cuttings in their flowering room as soon as they cut them from the veg mother or a flowering mother plant. This method lets the cuttings begin flowering even before their roots have formed. 

However, you must not give any nutrients to a clone that has not yet rooted! Conversely, you must not transplant a clone that has already been given bloom food.

Here’s an example:

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These cuttings were taken from a flowering plant and placed in water to root while flowering. 

DO NOT add early bloom nutrients to cuttings like these until they are rooted and transplanted, even though they are flowering. 

Wait at least three days after transplant to provide flowering fertilizers.

Therefore, transplant your clones once they have a strong root system before introducing chemical or organic bloom fertilizers. 

If you implement a similar system in your cannabis garden, it might be several weeks after the clone has started flowering before you should apply a flowering fertilizer. 

Grower’s Tip: Clones can be more delicate than plants grown from seed, especially when roots are first developing. Therefore, go light on the flowering fertilizers at first, increasing the dose slowly over time.

Should I Give Flowering Fertilizers to Outdoor Plants, and When to Start?

Outdoor cannabis plants rooted in the earth seldomly require fertilizers when switching to the flowering cycle. Nature provides everything they need. 

Cannabis plants grown indoors depend on organic or chemical fertilizers (or both) to be productive in flower. 

Since there may be ethical or even legal questions about using chemical fertilizers outside, outdoor plants should always be fertilized with natural, organic teas.

If you are compelled to fertilize your outdoor cannabis plants, start using bloom fertilizers after the summer solstice.

If your outdoor cannabis plant is in a container, such as a flower pot, then apply the same standards for switching to flowering fertilizers that you would for indoor plants. Indoor and outdoor container-grown plants will need added fertilizers.

Key Takeaway: Outdoor plants in containers need flowering fertilizers. Outdoor plants that are on the earth do not need flowering fertilizers.

How to switch to flowering nutrients

Using the timing cues described in this article, start using flowering nutrients no sooner than one week after the most recent veg feed. 

Also, flush your soil generously with plain water once or twice before implementing flowering nutrients.

Note: This is not a pre-harvest flush. Just apply water until you see approximately 25% run-off. This helps remove excess veg nutrients in the substrate. Let the substrate dry for two or three days. Then, switch to flowering fertilizers.

Also, when you switch from veg to early bloom nutrients, add micronutrients to the fertilizers for optimal plant health and nutrient uptake during the flowering period. 

Once is enough to apply micronutrients. This will help your plants to stay healthy and strong throughout the flowering cycle.

What Flowering Nutrients are Best for Cannabis Plants?

There are countless veg, early bloom, and late bloom nutrient formulations on the market. Here is a general guideline for cannabis fertilizers, though different product formulations will vary:

  • Veg fertilizer: 3-1-1 N-P-K

Veg fertilizers are heavy in nitrogen, low in phosphorus and potassium.

  • Early bloom fertilizer: 1-3-2 N-P-K

Early bloom fertilizers are low in nitrogen, high in phosphorus, and medium in potassium.

  • Late bloom fertilizer: 0-0-6 N-P-K

Late bloom fertilizers have no nitrogen or phosphorus but are heavy in potassium.

Is it Safe to Foliar Feed Chemical Fertilizers on Flowering Plants?

Many gardeners apply foliar nutrients when feeding their plants during the veg cycle. Yet, it might not be safe to apply foliar sprays onto cannabis flowers. Therefore, feed your flowering plants at the plant’s base, into the root zone.

Combusting fertilizers and inhaling them could be dangerous. If you have residue remaining on your buds after foliar feeding and you smoke it, you might be harming your lungs.

How to Use Bloom Fertilizers on a Male Cannabis Plant?

The moment your plant shows sex is always a great time to provide its first early flowering nutrient feed, even if your plant is a male. However, males typically don’t need much bloom fertilizer (if any) because males don’t produce heavy flowers as female plants do. 

If you fertilize a male cannabis plant, wait until you see the first set of pollen sacs at the top node of the plant before switching to bloom nutrients. 

Whereas a female plant produces pistils when she reaches sexual maturity, male plants reveal round balls that will grow into large pollen sacs. As soon as you see these round balls at the top of the plant, you can feed them with flowering nutrients.

James Alexander James Alexander
Hey, I'm James! The founder and head writer here at GreenBudGuru.com. I started this site to share my passion and knowledge of all things cannabis. I used to work as a budtender in central Amsterdam, and have over 7 years of growing experience.

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