Autoflowering Cannabis Flowering Time

Autoflowering cannabis seeds are also popularly known as autoflower, automatic or auto seeds. One of the main characteristics of these strains is that the beginning of their flowering stage does not depend on the number of light hours they receive (photoperiod). For autoflowering plants, flowering is triggered automatically when they reach approximately three weeks of age. But exactly… how long does an autoflower take to flower?

The flowering period of an autoflowering cannabis plant lasts around 4–5 weeks, a feature that makes them very attractive to home growers seeking almost instant results from their cannabis plants. Their key characteristics include:

• Fast growth and flowering: The plants are ready to harvest only 8 to 9 weeks after germination and the appearance of cotyledons. The vegetative growth phase typically lasts around 3–4 weeks.
• Cost-effective growing: Since their flowering period is short, they are exposed to pests and adverse weather conditions for less time. Additionally, they require fewer resources such as fertilizers, electricity, and labor.
• Discretion: With a short life cycle and an average height that usually does not exceed one meter, these plants are very discreet, making them perfect for home growing on balconies and in pots. Their discreet size helps avoid prying eyes and reduces the risk of plant theft.
• Resistance to fungal attacks: Autoflowering plants are perfect for spring growing and can be harvested before the end of summer and the rainy season, which often brings fungal attacks that can devastate large, beautiful buds.
• Immunity to light “contamination”: Since these strains do not depend on the photoperiod to initiate flowering, they are unaffected by light pollution from streetlights or other artificial lighting. In contrast, photoperiod-dependent plants are sensitive to light pollution, which can disrupt their flowering process.

At Sweet Seeds®, we are a pioneering seed bank in the development and improvement of modern feminized autoflowering genetic lines. Our autoflowering strains complete their flowering cycle in just 4–5 weeks, allowing you to harvest delicious flowers in as little as two months after germination.

From Autoflowering Seeds to Harvest

The main characteristic of autoflowering cannabis seeds is their short life cycle. But… how long does an autoflower take to flower? These plants flower automatically upon reaching a certain age, without depending on any specific daily light hours to enter the flowering stage. They allow growers to harvest in approximately 8–9 weeks after germination and the appearance of cotyledons.

Fast and discreet, they owe these traits to the primitive genetics of Cannabis Ruderalis. This subspecies of Cannabis Sativa L. originates from regions in Eastern Europe (Hungary, southern Siberia, Russia), Central Asia, and wild areas of North America and Canada—places with short growing seasons and generally low temperatures.

Although all autoflowering seeds develop quickly, the final size and life span of the cannabis plant depend significantly on the genetics and the environmental conditions provided by the grower.

Which Autoflowering Strain is the Fastest?

Generally, autoflowering strains take about 3–4 weeks from germination to start flowering, followed by another 4–5 weeks of blooming, completing their life cycle in roughly 8–9 weeks total. With autoflowering strains, the flowering process is similar for both indoor and outdoor grows. However, results can vary slightly depending on the genetics selected. Indica-dominant strains tend to flower faster than Sativa-dominant strains. In fact, some autoflowering strains can complete their flowering in as little as 20 days.

Among the fastest autoflowering strains from Sweet Seeds®, we can highlight a few:

+Speed Auto® (SWS27)

This is the fastest strain in the Sweet Seeds® catalog. This strain is the resulting hybrid from the cross between an autoflowering selected genetic line of Critical Mass from the Sweet Seeds® R&D Department, selected for its fast flowering and pleasant, intense aroma, with a selected genetic line of our Speed Devil #2 Auto® (SWS25), known for its ultra-fast flowering. Growers can harvest this plant in just 7 weeks from seed germination.

Fast Bud #2 Auto® (SWS23)

This is an autoflowering strain that produces abundant harvests of large, resinous buds with a rich aroma. This strain features a well-balanced Indica-Sativa profile and produces highly vigorous plants with large lateral branches. The harvest time of this autoflowering strain, both indoors and outdoors, is approximately 7 and a half weeks from seed germination.

Sweet Skunk Auto® (SWS34)

This strain is an autoflowering tribute to the classic and beloved Skunk family. It is fast, easy to grow, and the mature flowers produce a very fruity flavor. As a predominantly Indica autoflowering strain, the plants start flowering about 3 weeks after the germination of the seeds. Harvest is usually ready around 7 and a half weeks from seed germination.

Which Autoflowering Strain Takes the Longest to Flower?

In general, Sativa-dominant strains tend to take longer than Indicas, as their flowering stage is usually more extended. These autoflowering strains develop slower than the faster strains, but they can reach greater heights and produce larger yields. Among the longest flowering yet most productive autoflowering strains in the Sweet Seeds® catalog, we highlight the following:

Big Devil XL Auto® (SWS28)

One of our longest-flowering autoflowering strains. This predominantly Sativa strain reaches heights of 110 cm to 160 cm, making this version significantly taller than its predecessor, Big Devil #2 Auto® (SWS20). As an XL version, it far surpasses the height of the original. The plants are ready to harvest approximately 9 weeks from seed germination, both indoors and outdoors.

Jack 47 XL Auto® (SWS78)

This strain is an extra-large version of one of our most beloved autoflowering strains, Jack 47 Auto® (SWS31). Predominantly Sativa, this classic autoflowering strain displays strong hybrid vigor and produces abundant, highly resinous, and aromatic buds. It is also one of the most potent autoflowering strains on the market, with THC levels reaching 21%. The plants can reach heights of up to 130 cm, and harvest time is around 9 weeks after the germination of the seeds.

Gorilla Girl XL Auto® (SWS82)

The wildest autoflowering girl in the Sweet Seeds® catalog, presented in an XL version. This Super Strong, tall strain is the result of crossing two powerful American strains from the Cookies family: Gorilla Girl® (SWS74) × Sweet Gelato Auto® (SWS76). Sativa-dominant, this strain delivers a potent effect and produces extremely high THC levels, up to 25%. Some specimens can reach heights of up to 120 cm, with harvest times similar to the previous strains—around 9 weeks from seed germination.

Stages of Growth of an Autoflowering Strain

In general, all cannabis plants go through three stages of development: vegetative, pre-flowering, and flowering. Although autoflowering seeds complete their life cycle faster, they follow the same sequence of development. However, autoflowering cannabis plants switch phases automatically once they reach a specific age, around 21 days after germination. In other words, autoflowering plants begin to flower after a specific time and do not depend on the photoperiod.

We have seen how long an autoflower takes to flower, and now we will review each stage of its life cycle one by one:

Vegetative Stage

The approximate growth period for autoflowering cannabis seeds is around 3-4 weeks. During this time, the plant will develop stems, leaves, branches, and roots, building its structure using air, light, water, and nutrients.

As the weeks of vegetative growth progress, you will notice new leaves developing, which help with photosynthesis. It is essential to provide a suitable growing environment to ensure the plant grows healthy and strong, so that it can be ready for the flowering stage. It’s important to bear in mind that a successful flowering stage largely depends on optimal development during the growth stage.

It is best to plant seeds in small pots of about 1 liter. This way, when watering, the soil will not stay wet for too long, improving aeration and root development. It also helps prevent slow or stunted root growth, nutrient deficiencies, or even fungus contamination in the roots of the plants.

During the early days of growth, it is crucial that the roots remain healthy. Any root problems, deficiencies, or stress in the first stages of an autoflower’s growth can significantly reduce the plant’s height and yield. Once the plant reaches twice the pot’s height, you can transplant it into a larger pot of 7 to 11 liters or even bigger.

Pre-flowering Stage

Autoflowering cannabis plants usually begin their pre-flowering stage about three weeks after entering the vegetative stage, meaning the growth phase is about to end.

It is important to recognize when autoflowering plants start to flower because this marks some sort of hormonal shift that affects the plant’s nutritional needs. During this stage, the plants will require a bloom-specific nutrient formula with higher doses of phosphorus and potassium, which are essential for bud production. It is easy to identify the beginning of pre-flowering: you will see the first flowers appear at the nodes on the stem and branches.

Flowering Stage

After the first flowers appear, buds will start to form, and the plant will enter the flowering stage. During this flowering stage, autoflowering plants usually need more phosphorus, potassium, calcium, and magnesium, while requiring less nitrogen.

As the final phase of flowering approaches, it is advisable to begin flushing the roots. This involves watering the substrate thoroughly and allowing it to drain for a few minutes. You can use specialized products to aid in the flushing process, helping to remove excess nutrients more effectively from the roots of your plants. As a result, the leaves may start to lose color and eventually fall off. Generally, autoflowering strains will begin flowering around 3-4 weeks after the cotyledons appear, and the flowering stage will last for about 4-5 weeks.

How to Know if My Autoflowering Plant Is Ready for Harvest?

Autoflowering strains usually finish their flowering stage about 8 weeks after the germination of the seeds. The buds will appear dense, compact, resinous, and aromatic, giving you an idea of how they will look after harvest. In general, there are two key aspects to determine the ideal harvest time:

1. The Color of the Trichomes:

This is the most precise method and involves carefully observing the color of the heads of the trichomes. You will need a jeweler’s loupe, thread counter, or a field microscope to detect changes in trichome color. The general rule is to harvest when around 20% of the trichomes show amber tones, with the rest appearing milky white. This is considered the optimal time to harvest autoflowering cannabis plants. However, you can adjust your harvest time slightly depending on the strain and the effect that you prefer. It is well-known that the choice regarding the harvest time directly affects the amount of resin produced, as well as its quality and cannabinoid profile. For a more energizing and cerebral Sativa-type effect, harvest a bit earlier than you would usually do. For a more relaxing Indica-type effect, let the plant mature slightly longer.

2. The Stigmas of the Flowers:

This is the easiest and simplest method to determine when your autoflowering cannabis plants are ready to harvest. It involves observing the color of the flower pistils (the two small white hairs emerging from the flowers). When approximately 75% of these stigmas turn dark brown, it is time to harvest your autoflowering cannabis plants.

Sweet Seeds®: High-Quality Results, Fast and Convenient

Autoflowering seeds complete the flowering stage very quickly and deliver high-quality results in extremely short periods. In just 8 weeks, you can have your harvest ready.

Additionally, because we know that size matters, at Sweet Seeds®, we have introduced our XL line, composed of autoflowering strains that grow taller and produce higher yields without compromising the high quality of aromas and flavors that are a hallmark of our seed bank.

At Sweet Seeds®, we encourage you to explore our range of autoflowering seeds and expand your seed collection with these genetics. We have invested great effort to preserve the best traits of each strain, focusing on maintaining the quality that defines us.

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Sweet Seeds S.L. is not responsible for any misuse of the information provided in this article. Growing Cannabis may constitute a criminal offense or administrative infraction; please check the Cannabis legislation applicable in your place of residence. Sweet Seeds S.L. does not, under any circumstances, intend to promote illegal practices. del mal uso de la información contenida en este artículo. El cultivo de Cannabis puede ser constitutivo de delito o de falta administrativa; consulte la legislación sobre Cannabis en su lugar de residencia. Sweet Seeds S.L. no pretende en ningún caso incitar a prácticas no legales.