When Does Cannabis Flowering Start Outdoors?

Cannabis flowering timelines depend on a variety of factors. Generally, in the northern hemisphere most cannabis strains will begin to flower at the start of August, give or take a few weeks. However, the flowering time of your plants will depend on its genetics, environment, and growing practices.

Our outdoor cannabis grow guide covers the plant’s growth timeline and the factors that can influence its speed of growth and flowering.

If you want to be prepared for the coming flowering season, our guide will help you time your outdoor cannabis garden planting and harvesting for best results.

Outdoor cannabis plants generally begin flowering around August, when the natural shift in daylight hours triggers the bloom phase. This shift typically occurs after the summer solstice, as the days start to get shorter and signal to the plants that it is time to begin flowering.

Photoperiod cannabis plants typically begin flowering after the summer solstice when daylight hours decrease.

During the plant’s vegetative stage, it focuses on growing stems and leaves. When the days get shorter outdoors, cannabis plants begin to make buds (around late summer).

After the switch, cannabis plants can nearly double in height.

Introduction to Cannabis Flowering Stage

The cannabis flowering stage marks the most crucial period in the life cycle of cannabis plants. This is when female cannabis plants shift their energy from vegetative growth to producing the resinous buds that growers seek.

The onset of the cannabis flowering stage is triggered by a reduction in light hours, typically when plants receive about 12 hours of light and 12 hours of darkness each day.

The flowering stage occurs when plants receive longer hours of uninterrupted darkness, signaling the transition to this critical phase.

The length of the flowering stage varies depending on the cannabis strain, ranging from 7 to 14 weeks. Understanding the timing and requirements of the flowering stage is essential for growers aiming to maximize both the quality and quantity of their harvest.

By recognizing the signs that plants are entering this phase and adjusting care accordingly, cultivators can ensure their cannabis plants reach their full potential.

How Genetics Influence Growth in Cannabis Plants

Genetics play a big part in the rate of growth and the time of flowering of your cannabis plant. For best results, consult the marijuana strain’s growth timeline to plan your plant’s growth.

Fast flowering strains, such as certain indica-dominant varieties, can complete their flowering phase more quickly than others, sometimes in as little as 6-7 weeks.

Indicas vs. Sativas Cannabis Strains

Indica plants, which are typically shorter and bushier, tend to finish earlier than sativa strains, so their flowering stage comes sooner.

Indica strains have a flowering stage about 8 weeks long. For sativa strains, the flowering stage can take up to 10 weeks.

Landrace and Haze strains can take considerably longer than most strains to flower. Landrace strains that are grown outside of their native environment tend to take longer to grow and may develop smaller flower buds.

Autoflowering Strains

Autoflowering strains have different growth timelines than photoperiod strains. Autoflowering strains do not need a change in light cycle to begin their flowering phase.

Instead, they automatically begin to flower after a certain period of time. Autoflowering cannabis plants start flowering naturally 3-6 weeks after germination regardless of the light cycle.

In autoflowering strains, the vegetative and flowering stage time varies and depends on the strain's genetics.

The vegetative stage usually lasts between 3 to 4 weeks. Autoflowering strains can take up to 10 weeks to complete their entire life cycle.

How Environment and Growing Practices Influence Growth

Cannabis seeds can be planted between April and July. Many growers choose to plant their cannabis seeds in early June. When you grow seeds, it's important to monitor environmental factors to ensure healthy early development. The timing of your planting depends on your strain and how big you want it to get.

If you want to give your plants the most amount of vegetative time to grow, you should plant them earlier rather than later.

For instance, planting seeds in May can provide growers with about 3 months of vegetative time before the days get shorter and they start flowering.

Depending on your location some growers have the advantage of getting a long vegetative cycle if they want it. If you don’t want really tall plants, you can try pruning, low stress training (LST), or planting seeds later than normal.

A shorter vegetative phase may be desired if you want to limit the size of your plant.

For a short vegetative stage, you can plant your photoperiod cannabis seeds later in the planting season. This gives them a shorter time window to grow before the shorter daylight triggers flowering.

During the vegetative stage, vegging plants require specific water and nutrient needs to support healthy growth before transitioning to flowering.

During the plant’s pre-flowering stage in the vegetative period, cannabis plants will begin to develop their pre-flowers. If you do not know the sex of your plant by this point, monitoring the pre-flower formations can tell you if it is a male or female.

Male plants can be identified by the development of pollen sacs, which should be removed to prevent pollination of female plants. Female plants are the ones that will produce buds, so distinguishing them from male plants is crucial.

Preparation for Flowering

Proper preparation before the flowering stage is key to achieving healthy bud development and a successful harvest.

Start by ensuring your plants are robust and free from pests or diseases, as any issues during the vegetative stage can carry over and impact bud formation.

It’s important to provide a balanced nutrient profile, supporting strong root systems and healthy foliage without encouraging excess foliage that can block light from lower bud sites.

Many growers use pruning or training techniques, such as topping or low-stress training, to shape the canopy and promote even light distribution, which helps maximize bud growth.

For most cannabis strains, the transition to the flowering stage is initiated by changing the light cycle. Indoor growers can control this by switching from an 18/6 (18 hours of light, 6 hours of darkness) to a 12/12 light cycle, signaling to the plants that it’s time to start flowering.

Make sure your grow room can accommodate the potential stretch in plant height that often occurs as plants begin to flower. By preparing your plants properly and managing the light cycle, you set the stage for a productive flowering phase.

Outdoor Cannabis Flowering Stage Timeline

The cannabis flowering phase is the period when plants shift from vegetative growth to bud production, marking a critical stage in the cannabis lifecycle.

As the marijuana flowering stage begins, plants grow rapidly and enter early flowering, which is characterized by a noticeable stretch in height and increased nutrient needs. This initial period, known as the flowering stretch, is when plants grow the fastest, so it’s important to manage space and support stems as needed.

During mid flowering, you’ll notice significant changes: cannabis buds become denser, resin production increases, and pistils may start to change color. This is also when growing buds are developing quickly, and you should monitor for signs of healthy bud formation and maturing flowers.

As you approach the late flowering stage, typically in the final weeks before harvest (weeks 6 to 8 for most strains), focus on monitoring trichome development, pistil color, and overall bud ripeness.

The final weeks are crucial for flushing your plants, maintaining optimal relative humidity, and preparing for harvest to ensure the best possible quality.

In the final week, check for full maturity and readiness for harvest by examining trichomes and pistils closely.

Final harvest times for most cannabis strains indoors typically occur after 8-10 weeks of flowering.

Throughout the cannabis flowering phase, pay attention to how your plants grow and develop. Watch for the formation and ripening of cannabis buds, noting changes in size, density, and aroma.

Fan leaves play a vital role in photosynthesis, so manage them to optimize light exposure and airflow, which helps prevent mold and supports bigger buds. Heavy buds in flowering can require additional support to prevent branches from breaking under weight.

Use flowering nutrients and boosters to encourage bigger buds, but be careful to avoid nutrient burn by not overfeeding. Watch for signs of nutrient deficiency, such as yellowing leaves or poor bud development, and address them promptly.

Flowering cannabis plants generally prefer slightly cooler conditions than vegetative plants, around 20-24°C (65-75°F).

Finally, remember that some yellowing or leaf loss during flowering is completely normal and simply part of the plant’s natural lifecycle.

Nutrient Requirements for Bud Formation

As cannabis plants enter the flowering stage, their nutrient needs shift to support the development of dense buds and healthy flowers.

During this period, flowering plants require higher levels of phosphorus and potassium, which are essential for rapid bud growth and strong flower production.

While nitrogen is important during the vegetative stage, it should be reduced in the flowering phase to avoid excess foliage and encourage the plant to focus on bud sites.

During the flowering phase, cannabis plants become more sensitive and require closely monitored care to avoid issues.

Most growers switch to specialized bloom nutrients at the start of the flowering cycle to provide the right balance for healthy bud formation. It’s important to monitor your plants closely for signs of nutrient deficiencies or excesses, such as yellowing leaves or nutrient burn, and adjust feeding schedules as needed.

Maintaining proper nutrient levels throughout the flowering period helps ensure robust bud development, maximizes yields, and reduces the risk of issues like bud rot.

By understanding and meeting the specific nutrient requirements of flowering cannabis plants, growers can support vigorous growth and achieve a successful cannabis harvest.

Detailed Flowering Stage Timelines

While the flowering stage is often divided into early, mid, and late phases, growers benefit from a week-by-week guide. Here’s a more detailed breakdown:

• Week 1–2 (Transition Stage): Plants stretch significantly as they adjust from vegetative to flowering. First white pistils begin to appear at bud sites.
• Week 3–4 (Early Flowering): Budlets form, and the plant’s energy shifts from vertical growth to flower production. A strong aroma may begin to develop.
• Week 5–6 (Mid Flowering): Buds gain density, trichomes start to form, and resin production increases. Pistils multiply and darken slightly.
• Week 7–8 (Late Flowering): Buds swell to full size. Trichomes turn from clear to milky, signaling peak cannabinoid production.
• Week 9+ (Ripening): Depending on strain, flowering can extend 9–14 weeks. Growers monitor trichomes closely; when they turn mostly milky with some amber, it’s the ideal harvest window.

Harvesting and Curing

The flowering stage doesn’t end until harvest, and knowing when to cut plants down is key:

• Signs of Ripeness: Look for trichomes that are mostly cloudy/milky with some turning amber. Pistils should be 70–90% darkened.
• Harvest Timing: Harvest too early, and potency and yield suffer; too late, and THC may degrade into CBN, creating overly sedative effects.
• Drying: Hang branches in a cool, dark, well-ventilated area for 7–14 days until stems snap instead of bend.
• Curing: Place dried buds in airtight glass jars, opening daily for the first two weeks to release moisture. A proper cure enhances flavor, aroma, and smoothness, while also stabilizing cannabinoids and terpenes.

Common Problems During Flowering

The flowering stage is vulnerable to multiple issues that can reduce yields or ruin crops:

• Bud Rot (Botrytis): Grey mold forms inside dense buds. Prevent with strong airflow, humidity control (40–50%), and regular inspection.
• Powdery Mildew: White powder-like patches on leaves and buds. Treat with organic fungicides (sulfur, neem oil) and reduce humidity.
• Nutrient Deficiencies: Yellowing leaves or burnt tips may signal imbalance. During flowering, plants need more phosphorus and potassium but less nitrogen.
• Pests: Spider mites, aphids, and thrips can thrive in flowering. Use preventative treatments like neem oil before flowering and beneficial insects during bloom.

Indoor Growing Considerations

Flowering indoors presents unique challenges and advantages:

• Light Schedule: Switch to a strict 12/12 light cycle (12 hours light, 12 hours dark). Even small light leaks can disrupt flowering.
• Light Spectrum: Red and orange wavelengths encourage bud development. Many growers switch from “veg” (blue-heavy) lights to “bloom” (red-heavy) during this stage.
• Airflow & Humidity: Use oscillating fans and exhaust systems to keep humidity between 40–50% and prevent mold.
• Temperature: Aim for 68–77°F (20–25°C). Cooler night temps can bring out purple hues in some strains.
• Training & Support: Indoor plants may need trellising, stakes, or nets to support heavy buds as they mature.

Learn to Grow Weed Outdoors at Cannabis Training University

If you want to learn more about flowering or how to grow a weed plant outdoors any place in the world, enroll in Cannabis Training University (CTU).

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Our comprehensive cannabis curriculum covers every aspect of cannabis cultivation for students of all skill levels. Learn everything about timing your planting, taking care of your plant, and harvesting at the right time in our marijuana growing classes.