Cannabis Flowering Stage Week by Week: What Your Plants Need

A cannabis plant in flower needs shorter days to kick things off, room to stretch in the first weeks, close attention to its sex, good odor control as the buds get stinky, and a well-timed finish. Outdoors, flowering usually starts in late summer as the days naturally get shorter. Indoors, you're the one who decides when it starts.

Most indoor growers flip their plants to flower after about four weeks of vegetative growth, but technically you can keep a plant in veg as long as you want.

Below is a detailed breakdown of a typical eight-week flowering stage. Some strains finish faster and others take longer, but this guide will show you what to expect as your plants close in on harvest and how to get the best possible buds out of this make-or-break phase.

Cannabis flowering weeks 1-3

The first three weeks of flower bring a bunch of big changes, and growers need to keep an eye on them to get the most out of their plants.

Week 1: the flowering stretch and a growth spurt

Right out of the gate, plants go through what's known as the flowering stretch, and growth speeds up noticeably. The stretch is the plant's natural response to switching into flower.

The plants reach for as much light as they can get, so the space between nodes grows and the whole structure opens up. Depending on the strain, some plants can double in size during this phase.

Week 2: sexing your plants and the first pistils

By the second week of flower, you can tell the sex of your plants. Females start pushing out long white pistils at the nodes, while males show little round pollen sacs.

Spotting the males and getting them away from the females is key to avoiding unwanted pollination, unless you're actually trying to make seeds.

Week 3: the focus shifts to flowers

In week three, plants start to wind down the stretch and put their energy into flowers. The buds are still small, but you'll see the calyxes getting bigger and the first trichomes showing up. Trichomes are the tiny resin glands that hold the cannabinoids and terpenes behind a plant's aroma and effects.

Cannabis flowering weeks 3-4

During weeks 3 and 4 of flower, plants focus on building bigger buds and pumping out strong, complex aromas. Here's what to expect during this crucial phase:

Bigger buds start to form

By now your plants should be done growing upward and putting all their energy into bud development. You'll watch the buds get thicker and denser day by day, with more and more resin piling up as trichomes.

Stronger, more complex aromas

Over these weeks, the smell coming off your plants gets more noticeable and more complex. As buds mature, they release a whole range of aromatic compounds, terpenes included, that give each strain its signature scent.

Expect intense aromas that run from sweet and fruity to earthy and spicy, depending on the genetics and other environmental factors.

Cannabis flowering weeks 4-6: peak bloom

During weeks 4 to 6, cannabis hits full bloom, and the big, dense buds you'll eventually harvest really start to fill out. Here's what to expect:

In full bloom: what buds look like as they fill out

In these weeks, your weed plants are in full bloom, which means the buds are growing as fast as they ever will. They should be getting big and dense, and covered in white pistils.

You may notice the calyxes, the small teardrop-shaped pods that stack up to form each bud, getting larger, and the buds looking denser and heavier than in previous weeks.

Aroma at its peak

This is when the smell of your cannabis peaks. The buds are building a thick coat of trichomes, the resin glands that hold the plant's aromatic compounds.

The result is a strong, pungent smell that's unique to each strain. If you haven't already, now's a good time to set up an exhaust fan and a carbon filter to keep odors under control.

Weeks 6-8: late flower and getting ready for harvest

Weeks 6 to 8 are the final stages of the plant's life cycle. Here's what to watch for as harvest closes in:

Dense buds caked in trichomes

In these last weeks, buds should be dense, firm and covered in a thick layer of trichomes, the resin glands that hold the cannabinoids and terpenes. The trichomes will start changing color, going from clear to milky white, with a few turning amber.

Flushing and prepping for harvest

During the last two weeks before harvest, many growers flush their flowering plants with plain, pH-adjusted water. The idea is to wash out nutrient buildup in the growing medium and push the plants to use up the nutrients stored in their leaves, which many growers believe helps keep the buds' natural flavor.

Some leaves will turn yellow during this process, and that's normal: the plants are burning through their nutrient reserves.

When to harvest

The best time to harvest comes down mostly to trichome color. When most of the trichomes have turned milky white and a few are amber, it's time to chop.