This article is about the Cannabis plant life cycle, divided into stages. You’ll find information about what to expect from the plant’s growth at each stage, some of the plant’s basic needs and what to watch out for!
- Storing your Cannabis seeds
- Cannabis seed germination (3 to 10 days)
- Cannabis seedling stage
- Vegetative stage (3 to 16 weeks)
- Flowering stage (8 to 11 weeks)
- When to harvest?
Cannabis growth is divided mainly in seed germination, seedling, vegetative, and flowering stages. Each one has its own environmental and nutritional needs, even different photoperiods. Let’s find out…
Storing your Cannabis seeds
This is how the life of a Cannabis plant begins. A viable seed looks brown with some stripes, dry and hard to the touch. If it feels weak or it’s white or light green, it’s probably an undeveloped seed and it won’t produce a healthy plant.
Keep your seeds in a dark, cold place, for example, in the fridge inside a plastic bag for better conservation. When the time of germination comes, get your seed out in ambient temperature. You can better your germination chances by putting your seed no more than 12 hours in a glass of water; if it floats it’s probably not viable, although it may germinate anyway. If it sinks, it’s probably because it’s viable and full of life, ready for germination. Don’t let it in the water for much longer, as the seed needs to breathe and it may drown and die.
Cannabis seed germination (3 to 10 days)
For germinating, Cannabis seeds need warm temperature, humidity, air, and water. Place them in a dark, warm, and humid place, for example between two plates in a damped napkin.
When the seed opens up and starts showing the first white tap root, it’s time to put it in its next growing medium (soil, coco, etc) in a small pot. This root starts to develop and eventually the plant produces the first two oval leaves, called cotyledons. Now it’s a seedling!
Cannabis Seedling stage (2 to 3 weeks)
Factors that lead to the healthy growth of Cannabis seedlings
- Warm temperature, around 22 – 27º C
- Relative humidity: around 65 – 80%.
- Low light intensity, blue spectrum preferred
- Adequate light distance (hand test)
- Light/Photoperiod: 18 hours of light / 6 hours of darkness.
- Nutrition: a low dosage of nutrients for start, then increasing
- Small pot size: Once germinated, place your seed/seedling in a small pot or cup with drainage for better results
- Watering: Water your seedlings with a sprayer to avoid overwatering
- pH levels: between 6.5 and 7
Here’s how the seedling stage begins: when the seed opens, the first pair of small round leaves that appear are called “cotyledons”. After that, the little Cannabis plant starts producing serrated leaves, not the characteristic digitate leaves, only single serrated leaflets. As the seedling grows, new leaves with more leaflets start to develop until the plant produces digitate leaves with serrated borders we can all identify as Cannabis fan leaves. When these leaves appear, the plant enters into the vegetative stage. This process may take up to three weeks.
Cannabis seedlings growing conditions
Cannabis seedlings like relatively moist conditions. Temperatures should remain warm and lights should be placed near the plants and moved up as they grow. Finally, these baby plants need little amounts of nutrients and their needs will grow as the plant gets bigger and stronger.
Always check lights, airflow, limit the watering to its minimum and keep them in a small pot for a few days instead of planting it in its final container. This helps the root system to develop easier and stronger, with less risk of overwatering and drowning your little plant. Check your seedlings are receiving enough light, or else they’ll grow very tall and weak, with few leaves and a stretched white stem.
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Cannabis vegetative stage (3 to 16 weeks)
Factors that lead to the healthy growth of Cannabis in the vegetative stage
- Warm temperature, around 22 – 26º C
- Relative humidity: around 40-60%
- Increased light intensity / blue spectrum
- Adequate light distance: hand test
- Good airflow, extraction and CO2 intake.
- Light/Photoperiod: 18 hours of light / 6 hours of darkness
- Nutrition plan: Apply nutrients as needed – set a feeding schedule and follow it
- Bigger pot size: Once germinated, place your seed/seedling in a small pot or cup with drainage for better results. Transplant if needed to avoid becoming root bound.
- Watering: Water your plant regularly, avoid overwatering and watch for good drainage
- pH levels: between 6.5 and 7
In the vegetative stage, a healthy Cannabis plant grows in height and size as much as it can with the given conditions. Now the plant grows only leaves and stems. Meanwhile, it may show pre-flowers to indicate sex but the buds will only start growing when the days grow shorter, in Autumn, or the photoperiod is changed to 12/12.
How long does the vegetative stage take?
Most growers vegetate their indoor plants for 4-8 weeks, depending on the desired plant size. Cannabis plants are, depending on their strain, able to start flowering from the 4th week of the vegetative stage, but those plants will be smaller. Giving your plants more vegetative time will result in bigger plants and more likely to produce higher yields. In indoors, you must change your lights timer to a 12/12 hours schedule to trigger the flowering stage. By week 6 from seed, some Cannabis plants are able to start showing their gender by growing preflowers.
Male, female or hermie?
At this point, you should know (soon) if your plants are male, female or hermaphrodites. If you are growing with the intention of harvesting Marijuana buds, you should only allow female plants to grow and kill the males and hermies ASAP. Male and hermaphrodite plants soon start to pollinate the female plants and you’ll end up with lots of seeds and very little buds. As said before, only female plants produce buds, male and hermaphrodite won’t do it!
Full article: Determining the sex of your Cannabis plants
Flowering stage (8 to 11 weeks)
Factors that lead to the healthy growth of Flowering Cannabis plants
- Warm temperature, around (18 – 26º C)
- Relative humidity: around 40-50%.
- Higher light intensity, red spectrum preferred
- Adequate light distance: hand test
- Light/Photoperiod: 12 hours of light / 12 hours of darkness.
- Nutrition: a higher dosage of flowering nutrients
- Bigger pot size: Transplant to its final pot before starting the flowering stage
- Watering: Water as needed
- pH levels: between 6.5 and 7
Flowering stage indoors
To enter the flowering stage in indoor crops, the photoperiod must be changed to a 12 hours of light / 12 hours of darkness schedule.
It’s extremely important NOT TO INTERRUPT the hours of darkness (lights off) for the plant to start flowering correctly. If this dark period is interrupted, the plant gets “confused” and flowering may be delayed or worse, the plant may revegetate (go back to veg stage) or start producing hermaphrodite flowers. You definitely don’t want that to happen!
Flowering stage outdoors
Growing outdoors, plants will start the flowering stage when the days grow shorter, usually when Autumn is coming.
Autoflowering strains don’t need a photoperiod change to start flowering, their vegetative stage lasts around 4 weeks and then it changes stages automatically.
How long does the flowering stage take?
The duration of the flowering stage varies among different strains.
The flowering stage usually goes from 8 to 11 weeks, depending on the strain. It’s usually divided into weeks or three stages. The flowering period for Indica strains is typically around 8 weeks, but it may take up to 10 weeks. Sativa strains may take up to 10-12 weeks. Typically, hybrid strains will take up to 6-10 weeks to fully develop.
Flowering initiation – week 1-3
From week 1-3 plants stretch and grow in size and height. This phase is also known as the transition phase, as plants experiment drastic changes these days. Plants stretch and double their size in this phase. The female Cannabis plant starts blooming by producing pre-flowers, their pistils look “white hairs”.
Towards the end of the third week, the plant starts forming its bud sites in the plant nodes (where the main stem and the branches meet). Look for clusters of female preflowers.
All those places where white pistils have been growing are future bud sites. If you accidentally cut the preflowers along with the fan leaves, there’s a chance that that bud stops growing. You may lightly defoliate your plant during this phase, but be careful not to touch or damage the forming bud sites.
Look at the color of the fan leaves and the general look of each plant to have a better idea of their health and needs. The fan leaves should be vibrant green, not too light nor dark. For example, yellow and discolored leaves may indicate a deficiency, while dark and clawing leaves may indicate nutrient burn. Track these changes as soon as you notice them for a better chance of diagnosing your plants correctly and in time to heal them!
It’s also important to check for pests, mold, and fungi before our plants start making their buds. Most importantly, to eliminate these at this point is usually easier than doing it later into the flowering stage.
Mid-Flowering – week 4-5
From week 4-5 plants stop growing in size and start growing, fattening their buds and darkening their pistils.
- Humidity levels need to be lowered to 40-50%
- It’s best to slightly lower temperatures in flowering
- Temperatures with lights on 18-26 ° C (avoid high temperatures)
At this stage, you should continue to train your plant if you started some weeks earlier and you should be seeing some changes. In addition, if you need to tie or move your plants, bear in mind that now they are putting all their efforts into growing buds, so any stress or damage may slow that process.
Remember to continue to move your lamp or plants so they maintain their adequate distance. Now your plants are growing at a fast rate and they need their feeding and watering schedule to be followed for optimal results.
It’s normal at this phase to see some old leaves yellowing and finally turning brown and falling. That’s because some nutrients are “mobile”, meaning that once the plant has absorbed them, they can be stored and distributed inside the plant as needed. So an old leave may “send” nutrients to the newer ones and once the plant doesn’t need that leave anymore, it lets it die and fall. If you notice lots of leaves yellowing or any changes in color or texture in the new or old leaves, check for nutrient deficiencies or burn!
Late flowering / Ripening – week 6 to harvest
In the last few weeks, buds gain the most weight. They are sticky to the touch and can be very smelly. You are very close to reaching your goal = harvesting!
- Bring down humidity levels: 35-45% if possible
- Increase the temperature difference (day/night)
- Temperatures with lights on 18-24 °C
- Start checking trichomes for signals or ripening to know when to harvest
- Remember to flush your plants 1-2 weeks before harvest
Most importantly, buds are now covered in trichomes, which are rich glandules for secreting THC and other cannabinoids. These are responsible for the stickiness in the colas. Depending on the strain and the breeding, these buds may have strong aromas, reminding of fruits, flowers, and spices for example.
In this stage of the Cannabis plant, pistils may show white, cream and brown colors. They also start curling inwards and they get covered in trichomes. Similarly, trichomes also change colors and you should pay close attention to these changes because they are one of the best clues for knowing when is the best time for harvesting.
Remember you’ll need to do flushing prior to harvesting, so calculate your times in advance!
Flush for better results!
Flushing involves watering your plants with no nutrients added to “flush” all the salt excess from the roots. It may be done one or two weeks before harvesting (in soil) and in one day, two or more, depending on your feeding schedule and crop size. During this period between flushing and harvesting, plants use most of the nutrients they’ve been building up and the result is a much tastier and aromatic weed. If you don’t flush, those buds may have a bad and strong flavor and smell and may feel harsh on your throat when smoked.
Set reminders with the Grow with Jane app to start monitoring trichomes and pistils changes around week 6-7 with a magnifying glass or loupe to determine the best moment for harvesting.
When to harvest? (Week 8+)
Around week 8 of the flowering stage, buds will start fattening quickly. Likewise, you’ll see that trichomes and pistils are maturing and changing colors. Usually, when trichomes turn from transparent to a milky / white-ish color (and maybe 5-10% of them turn amber), your plant is ready for harvesting. In conclusion, it’s up to each grower the harvesting moment, depending on the effects and flavors desired.
We hope this guide helps you understand the Cannabis plant stages and life cycle. Now you know how much time each stage takes and what to expect.
Remember to download and try our Cannabis growing journal app, Grow with Jane! You’ll find lots of tools for planning and tracking your Cannabis crop through their stages, calculators, reminders, photos and much more coming soon! And it’s free!!