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Cannabis Flowering Stages Explained

The entire life cycle of marijuana plants is fascinating, but the flowering phase of the cannabis plant is where it’s at for cultivators. After germination and going through the seedling stage and vegetative growth, it’s time for action. This is when you’ll see your plants take their most significant stretch upwards and outwards, as well as the appearance of those all-important buds. In this article, we’ll take a closer look at what to expect and when to expect it as we present the cannabis flowering stages explained.

Errors during the flowering phase of growing cannabis can go a long way to make or break the size and quality of your eventual cannabis yield. Therefore, you must understand the needs of your plants at every step so you can take the appropriate action and treat your ladies with the right amount of tender loving care they need. We’ll help you by breaking down each stage of flowering and explaining what your plants are going through and what you need to do at each stage to optimise their potential. Bookmark this article and refer back to it when your plants begin flowering. All being well, you’ll see a bumper harvest by the end.

Stage One – Early Flowering/Preflowering

It’s important to note that cannabis plants don’t just exit the vegetative stage altogether and start producing buds. The first three weeks or so of flowering will likely see a considerable spurt, and it’s important to recognise this and care for your plants accordingly to help make this transition stage a healthy one. You’ll also want to take stock of your grow area and ensure you’ve got adequate space to accommodate the new growth of each plant as it progresses.

Week One

Prepare for lift-off – your cannabis plants will undergo a significant growth spurt. Many strains can double in size during this transition stage – for that reason, it’s often referred to as the stretch phase.

Your plants will begin packing on new mass and height, and you’ll see the formation of fresh leaves toward the top of the plant. Your plants are gearing up to bear fruit and are now producing adequate size to ensure that fruit can be carried. It helps to think of your plants reinforcing their structure – stems and leaves – to provide sufficient support for the upcoming new adornments.

Steps for Growers to take during Early Flowering

Nutrients

All this new size and new components mean extra feeding. Have you ever seen a teenager eat during a growth spurt? Your plant is much the same. Bigger plants need more sustenance, so be on hand with extra food at this stage, and your plants will thank you for it with quality buds in good quantity.

cannabis nutrients

Don’t skip to flowering nutrients right away, though. Keep up your nutrient schedule for veg growing initially, but increase the dose a little. Once flowering starts, give your girls about a week more of the growing stage nutrients before you reconfigure to flowering nutes.

Plant Training

The new stretch your plants undergo will cause changes in the way your plants stand – extra weight and size can lead to posture problems if left unaddressed, so now is a good time to bone up on plant training techniques and think about implementing them on your burgeoning beauties.

LST, or low-stress training, can help with eventual yields and is a worthwhile investment of your time. Bend those stalks down and away from the plants’ central core, and you’ll create a nice, even canopy that will utilise the light more efficiently, ensuring adequate light across a broader area of each plant.

Week Two

Things are heating up, and you can expect some exciting changes. For instance, in week two of flowering, you might notice the appearance of your first white pistils. These white, wispy hairs will rock up where the fan leaves join the plant’s main stem and are the first sign of a successful transition to flowering. These are the beginnings of bud sites and will later become those all-important buds, but it’s not time to rejoice just yet – more work lies ahead.

A warning – if, instead of seeing those fine white hairs, you start to notice tiny pollen sacs at the nodes, you’re dealing with a male plant, which won’t bear the type of fruit you’re hoping for. This is only a problem if you use regular seeds rather than feminized ones. If you see these sacs appearing, it’s time to swiftly remove these from any female cannabis plants in your grow room, lest they pollinate your fems and spoil your operation. A pollinated female won’t bud, so remove anything showing signs of sac production and keep them isolated away from the female plants.

Nutrients

Now is the time to switch up your nutrient schedule, away from growing and toward flowering. Check the instructions on your nutrients and change your delivery per the manufacturer’s recommendation. Failure to do this can hamper your yield potential, so don’t hesitate. Less nitrogen now, and more potassium and phosphorus. Make sure your concentrations fit the needs of your plants at this time.

Watering

Give your plants water a little less often than you did during the vegetative stage, ideally once every two or three days instead of daily.

Lights

For photoperiod strains, you’ll look to match up the light cycle during flowering. Get those timers set to 12/12 hours of light/hours of darkness if growing indoors under grow lights.

Week Three

Those hairs you noticed last week are now starting to take the shape of real buds, and all is going swimmingly. Thankfully, your plants won’t yet be particularly aromatic, as resin glands haven’t appeared in any significant number at this point.

Your plants are still growing at this stage and can be as much as 50% bigger than they were just three weeks ago. They’re also stretching somewhat, but you can expect that stretch to slow considerably and soon stop.

Your plants will now refocus all their energy on producing flowers (buds) instead of growing, as their frames should now be adequately equipped to handle the weight of the buds.

Nutrients

This is a critical step in terms of your plants’ nutrient requirements. Take great care to double-check that your nutrient schedule is on point, and dial in the correct dosages for the flowering stage. It’s game on now, and your input here can go a long way to determining your harvest.

Grower’s Checks

You should be checking the health of your plants intermittently throughout the operation, but at this stage in the game, it helps to know what to look out for. By this point in the growth cycle, your plants may begin to put out distress signals that make it easy for you to identify specific deficiencies.

For example, a common issue at this stage is yellowing leaves, indicating a condition called nutrient burn. This results from overfeeding nutrients to your plants, which can happen accidentally or as the result of an over-zealous cultivator looking to maximise bud production. If you see yellowing tips in the leaves of your plants, this is a sign of nutrient burn, and it’s best to dial back the amount of nutrients you’re giving your plants immediately.

Pruning

Now is an excellent time to grab a pair of shears and get pruning. All that extra mass on your flowering cannabis plants means there’s a chance airflow through the central body of the plant may be hampered. To avoid mold and other issues, prune away excess foliage from this area, and the airflow will be optimal and help reduce risks.

Week Four

By now, your plants should have stopped growing/stretching altogether, with all energy concentrated instead towards bud production. You should see those buds getting bigger and fatter by the day, and mark this as a sure sign that things are going well. Now is the time to elevate your odour control game, as growing buds means trichome production and cannabis reek.

Nutrients

If you’ve made it this far, you’re doing well – moreso if you’ve avoided nutrient burn. You’re doing great, so keep that feeding schedule as is, and feel free to consider using a flowering booster at this stage.

Plant Training

Your plant has stopped growing, so bending down branches is not something you have to keep doing. Conversely, you may need to think about ways to hold branches up – at this stage, such is the size of your plant, that it may be up to you to provide structural support to keep everything tight and together.

Week Five

Full flowering mode activated! Week five of the flowering stage should see bud production and growth taking off. Those dense nugs you’ve been dreaming of every night are now manifesting on your plants, and you’ll also start seeing new buds appearing along the main cola.

Things to Check

This is the time to ensure – if you’re growing indoors – that your ventilation is on point because the aromas from your plants will be strong. Check the pistil hairs on your plants – once white, they should now be starting to show signs of turning amber or brown. Eye your trichomes closely, too. If they’re becoming milky white and opaque, your plants are edging towards time for harvest.

Weeks Six, Seven, and Eight

In these weeks, many cannabis strains will be near ready to harvest.

Of course, not all strains have the same flowering time; some are ready quicker, while others can take nine weeks, ten weeks, or more. However, most cannabis strains will be in flowering for eight weeks before they’re ripe for the picking. This is where it helps to know your strain.

What’s the estimated flowering time for the plants you’re growing? Make a note, and then, two weeks from the end of the predicted flowering cycle, it’ll be time to flush your plants.

Week six will see your buds continue to grow and ripen. Week seven is more of a waiting game where not a lot will likely change other than a continued fattening of buds, darkening of the pistils, and trichomes becoming whiter. By week eight – depending on your strain, of course – at least half of the pistil will turn dark and begin curling back inwards toward the flower.

Cannabis flowering stages explained

Flushing Cannabis Plants

Flushing your cannabis plants means halting your nute delivery and administering only plain water for the last two weeks. Doing this will flush out the minerals and salts from the soil and ensure a better-tasting, smoother-smoking cannabis. After all your hard work and patience, the last thing you want is for the end product to have a chemical taste, so flush your cannabis approximately two weeks out before harvest to guarantee you can taste all the beautiful flavours and terpenes of your chosen strain.

Look out for Mold

Keep a close eye on your plants from top to bottom, and beware of the dreaded late mold! You’re approaching harvest time, but you’re not out of the woods. There’s still a chance of bud rot at this point, so be vigilant.

Support your Plants

Those flowering buds will be at their fullest and heaviest now, so ensure you provide ample support to your plants if they require it. Sticks and canes are your best bets here, so attach them to your plants using string to ensure adequate support for the extra weight of all those lovely big buds.

Eye Your Trichomes

Use a magnifying glass or similar device to inspect your trichomes. If they’re still primarily clear in their appearance, it’s not yet time to harvest. However, if they’re predominantly amber and opaque, this is considered a sign that the plant is ready to harvest. If this is you, and most of your pistils are darkened and curling inwards, THC content is near maximum, and it’s time to start pulling. 

Congratulations! Now you can enjoy the fruits of your labour (after drying and curing, of course).

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

Duncan Mathers