Cannabis Flowering Stage Week-by-Week: A Visual Grower’s Guide

In this guide, we are going to show you how you can make the best out of the flowering stage week by week. By the end, you will know what to look out for and practical steps to optimize the growing conditions for the developing buds.

What is the flowering stage of cannabis?

During veg, your plants stretch upwards and sideways to create potential bud sites. When the time is right, the plants stop growing to refocus their energy on producing flowers.

The flowering stage timeline varies from one strain to another due to genetic differences.

• Indicas finish in about 7-9 weeks.
• Sativas take more time and may need from 10 to 14 weeks for full maturation
• Hybrid strains combine the two and have more middle ground, with an average of 8-11 weeks
• Autoflowers are essentially hybrids, but they have an even faster flowering period of about 5–8 weeks.

This guide will paint a picture of the expected outcomes week by week over these timelines, taking into account the slight variations for each case.

Week 1-3

Primarily known as the pre-flower phase, the initial 1-3 weeks are very crucial in sex determination. This is the time that you get the very first signs that your plants are flipping from veg to flower.

First signs of the flowering stage

• The plants experience rapid vertical growth, often doubling or tripling their height in the first week. The stretch hits its maximum in the second week before slowing down.
• For male plants, their main sign of transition is the formation of pollen sacs that appear as small and rounded sacs at the node site.
• Female flowers show up with preflowers (first pistils) at the junctions between branches and the main stem. You will also see tiny white protrusions (stigmas) that look like hair strands.

Practical Grower’s Tips

Here is what you can do when you see these signs:

1. If you are after female flowers but have regular cannabis seeds grow, this is the time to remove the males from the grow room to prevent pollination of the flowers.
2. Adjust the lighting to feature longer hours of darkness and shorter periods of light to signal the production of pro-flowering hormones. This change also prevents further stretching, resulting in a tighter structure.
3. You can choose to flush the growing medium and remove excess minerals intended for the vegetative stage.
4. The pre-flower stage is the time to adjust the nutrition regimen to higher ratios of phosphorus and potassium, which aid in bud development.
5. Implement structural support for the lanky stems and branches to support the weight of the buds.

Weeks 4-5

Heavy Bud Stacking

After the pre-flower frenzy, faster-finishing varieties, such as autoflowers and some indicas, start stacking as soon as they enter week 4. The main indica colas form a dense cluster of nugs while autoflowers rack up their density.

One other thing you should notice is the first resin glaze, which will increase the intensity of the smell inside the grow room. Heavy trichome strains begin to form sugar leaves with tiny, glittering structures.

It is not surprising to see some sativas stretching late in week 4, continuing into week 5. However, the rate should have slowed down by now with the formation of numerous calyxes.

Practical Grower’s Tips

1. Lower the humidity levels to about 40–50% to prevent mold issues early on.
2. Install or ensure that your carbon filter is working properly to get rid of the intensifying terpene odor.
3. Continue feeding the plants with higher phosphorus and potassium ratios. These feeds boost the bud densities to increase their weight.
4. Now that all the bud sites are clearer, you can finesse your defoliation by shading fan leaves from obscuring your best bud sites.
5. What is the ideal PPM for cannabis flowering week 4? Generally, you can push for around 800 PPM, rising to 1000 PPM in hydroponics setups.

Week 6-8

Often referred to as the powerhouse period, week 6-8 is the time when cannabinoid production goes through the roof.

Peak Flowering and Maximum Resin Production

• Many autoflowers should be looking to end their cycle as early as week 6. You will notice a change in their pistils’ color to a few red and orange hairs.

• Indicas are usually done with canopy formation and are visibly focused on bud density.
• Sativas start to fill out their canopies. Their long and airy colas will also start connecting to create a more solid structure.
• With resin protection at its peak, expect an even stronger smell. The distinct aroma notes are also now more discernible at this point.

Practical Grower’s Tips

1. Grab a jeweler’s loupe to assess the maturity of trichomes for those early-finishing strains. They should be turning from clear to cloudy or milky.
2. As the bud density increases, watch out for straining branches so you can give them extra support. These branches can bend too low into the high humidity growing medium and away from light exposure and air circulation.
3. Sativvas can give you a window to do lollipopping or final structural pruning so as to get rid of popcorn buds at the bottom of the plant at the expense of the main colas.

Week 9-10

You are on the homestretch for many strains.

The Harvest Window

By now, most indica-dominant strains are fully focused on ripening their heavily stacked buds. Their pistil colors change dramatically, with 70-90% of them appearing dark or receded.

Pro Grow Tip : Harvest time is not about how many weeks are being counted, its about trichome maturity.  Milky and cloudy trichomes show peak THC.

The trichomes are the ultimate signal for you to start thinking of chopping the buds. Most growers wait until the trichome heads have turned 70% cloudy and about 15% amber.

While some sativa hybrids may start to show the signs above, original landraces should still be cruising in peak bulk mode.

Practical Grower’s Tips

1. Once the pistils and trichome heads start to change in appearance, flush the grow medium with pH-neutral water for about 7-14 days before harvest. Flushing improves the final taste of the buds.
2. If you want darker pigment expression, like purples, drop the temperatures slightly, mostly during lights out, to about 50°F to 65°F (10°C to 18°C)
3. Watch out for signs of nutrient deficiencies in the still-bulking sativas and keep humidity optimized.

Week 11-14

For the patient Sativa growers and some hybrids, it is finally time to start thinking of harvest.

Preparations for Sativa Harvest

Early on, you will notice leaves fading as the plant shifts to full-time bud ripening and consumes any energy reserves in the leaves.

Practical Grower’s Tips

What is the ideal trichome ratio for Sativa harvest? After flushing, your harvest day will depend on whether you want a more energetic high (mostly cloudy trichomes) or a heavier hit (more amber).

Takeaway

The flowering stage can be broken down into three distinct phases. We have pre-flower for stretching and sexing, peak flower for rapid bud stacking and trichome production, and finally ripening for trichome maturation.

Once you have nailed all of them, all that is left is proper drying and curing. The final potency, smell, and taste heavily depend on these next steps.

Bruno Eastman Cannabis Specialist / Content Writer

Bruno Eastman is a seasoned cannabis cultivation expert with over fifteen years of experience in the Cannabis Seed industry. Throughout his career, Bruno has managed some of North America's top cannabis growing facilities, earning recognition as an authority in the field. His expertise lies in understanding the intricate dynamics of cannabis plants and making the small adjustments that drive successful yields.

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