How to Grow Autoflowering Marijuana: Complete Step-by-Step Guide

Autoflowering marijuana seeds have become very popular with growers of all levels. Their fast cycle, which lasts between 8 and 12 weeks, and their small size (usually between 50 and 100 cm) make them an ideal choice for outdoors with little space, such as balconies or discreet gardens. As they do not require photoperiod changes to flower, their cultivation is easier than photodependent marijuana strains.

If you are thinking of getting started in this type of cultivation or want to improve your results, this guide offers you a clear, practical and updated vision on how to grow autoflowering marijuana from seed to harvest, both outdoors and indoors; you will also learn what mistakes to avoid and how to get the most out of your autoflowering cannabis plants, whether they are seeds rich in THC or with high CBD content.

Nota legal: Este artículo es informativo y está destinado a adultos en países donde el cultivo de cannabis está permitido. Infórmate sobre la regulación del cultivo de cannabis que se aplica en tu región.

What are autoflowering seeds?

The autoflowering seeds are those that flower automatically, without depending on the photoperiod (hours of light and darkness). This is due to its ruderalis genetics, a cannabis variety native to cold regions with short summers. These plants have a short life cycle, which usually lasts between 56 and 85 days from germination to harvest.

Unlike photodependent seeds, which need changes in the hours of light to start flowering, autoflowering seeds flower automatically, which greatly simplifies cultivation, especially for novice marijuana growers. These varieties can be either THC-rich marijuana or CBD-rich cannabis, depending on the genetics chosen.

Advantages and disadvantages of growing autoflowering plants

Advantages:

• Fast harvests: It is possible to obtain several harvests per year or to bring forward the harvest before the cold weather arrives.
• Small plants: They adapt well to small spaces such as balconies, terraces, gardens or closets.
• Easy to grow: Their need for nutrients is lower and they are at less risk of pests as they are exposed for less time.
• Resistant to cold: The ruderalis genetics makes them resistant to low temperatures. Autoflowering plants can be grown even in winter, as long as the temperature is above 15-16ºC.

Disadvantages:

• Lower production due to its reduced size, compared to the cultivation of larger photodependent feminized seeds.
• Little margin to correct mistakes: its fast cycle does not allow much time to recover from problems. Any problem (lack of light, excessive irrigation, transplanting, stress) directly affects the final yield.
• They cannot be transplanted many times: stress slows down their development, so they must be planted in their final pot from the beginning.
• Lower THC potency: although much improved, they are still somewhat lower than photodependent strains in most cases.

Once you have assessed the advantages and disadvantages of autoflowering strains, you can decide whether it is more convenient for you to grow autoflowering or photodependent varieties. If you want small plants that give a quick harvest and you are not so concerned about production, or you just want to get started in cannabis growing, autoflowering strains will suit your needs perfectly. On the other hand, if your priority is larger harvests and a higher THC content, then it is better to opt for feminized photodependent seeds.

Stages of autoflowering cultivation: week by week

Seed selection

Opt for quality genetics, taking into account resistance to cold, if temperatures are not very high in your area. Check characteristics such as weeks of cultivation, estimated production or THC/CBD content to make sure they are adapted to your objectives.

Week 1: Germination and first days

Germination is the first step to successful cultivation. You can use several germination methods. One of the most practical and safest is the use of jiffys (pressed peat or coco pellets). Jiffys are easily hydrated, retain the necessary moisture and allow excellent aeration for the young roots. You can also opt for the wet napkin method or plant directly into the substrate.

During the first days of germination, try to maintain a stable temperature between 20 and 25 ºC and high humidity (70-80%). In a few days you will see the cotyledons and the first true leaves. Ideally, move from the jiffy to the final pot (or soil) as soon as possible, when the first true leaves appear, to minimize stress to the roots.

Week 2-3: Planting and vegetative growth

If the soil is suitable and receives as much light as possible, it is preferable to plant directly in soil. Prepare the soil by turning and aerating the soil and applying compost to ensure a loose and nutritious soil that facilitates rooting. If you grow in pots, use large pots, which will be the definitive ones (at least 18 liters, preferably 25), of light colors, such as brown or white, rather than black.

If you have used jiffy to germinate, remember that before transplanting the plant you must remove the paper mesh that surrounds the jiffy soil.

During this first stage, the plant needs a base rich in nitrogen (N), since this nutrient stimulates the development of stems, leaves and roots. Growth fertilizers with NPK 3-1-2 or similar formulations are used. Use a quality substrate to achieve the best results, as these are already prepared with perlite and fertilizer, perfect for good drainage and optimal plant growth.

During the first weeks, the plant develops new leaves, stems and roots. It is essential that it receives the maximum possible light and that the substrate is neither dry nor waterlogged. Avoid transplants at this stage so as not to slow its development.

Week 4-5: Beginning of flowering

We will know that our plants are beginning to flower when the first white pistils appear, which mark the end of vegetative growth. From then on, the marijuana plants will stop stretching to focus on the formation of buds. It is essential to adjust the feeding to this new phase: the need for nitrogen is reduced and the need for phosphorus (P) and potassium (K) increases, so it is advisable to use a good flowering fertilizer, with formulas such as NPK 1-3-2 or 0-5-4.

Week 6-8+: Fattening and ripening of buds

The buds increase in size, density, aroma and resin content. You can apply a flowering stimulator if you wish. Towards the end of this phase, observe the trichomes with a magnifying glass to determine the best time to harvest. Indoors, maintain good ventilation to avoid fungus.

Root washing

Root washing is essential to improve the taste and final aroma of the buds. It is usually done 7 to 10 days before harvest, watering with plenty of clean water (pH adjusted) and applying at least twice the volume of the pot to wash away excess salts. After this process, the plant continues to ripen with water alone until cutting. The intensity of rinsing varies according to the type of fertilizer: with biological fertilizers it is sufficient to suspend their use 3 or 4 days before harvest and do a light rinsing, while with mineral fertilizers a more intensive rinsing is necessary to remove accumulated salts thoroughly.

When to harvest autoflowering plants?

The color of the trichomes of marijuana indicates the optimal point of harvest, the one that preserves the profile of cannabinoids and terpenes, which are the active principles of the plant, responsible for its flavor, aroma and effects. The trichomes are small glands that cover the plant, and are found in greater concentration in the flowers or buds of cannabis.

The best way to know when to cut is to observe the trichomes with a magnifying glass (minimum 30x):

• Transparent trichomes: still lacking development.
• Milky trichomes: maximum concentration of cannabinoids, potent effect.
• Amber trichomes: more relaxing and narcotic effect.

Most growers harvest when 70-80% of the trichomes are milky and 10-20% are amber.

How to identify mature buds in cannabis

How to grow autoflowering plants indoors

Growing autoflowering plants indoors is an excellent option to control all environmental factors and guarantee fast harvests all year round.

Necessary material for indoor cultivation

• Growing cabinet or a space with good ventilation and light control
• LED or LEC grow lamp
• Timer to program the hours of light (18/6) – Automates the switching on and off of the light to maintain a constant photoperiod.
• Extractor fan, intractor fan and oscillating fan – regulate the temperature, renew the air and prevent moisture accumulation.
• Definitive pots, preferably made of fabric, between 11 and 18 liters – They allow a good root development without the need of transplanting.
• Light and aerated substrate (a mixture of peat, coco and perlite) – favors oxygenation and drainage, ideal for autoflowering plants.
• Specific fertilizers for growth and flowering
• Jiffys or reliable germination system – Facilitate safe and stress-free germination for the seedling.
• pH and EC meter (optional but very useful) – Controls the acidity of the water and the concentration of salts for a balanced nutrition.
• Thermohygrometer to monitor temperature and humidity – Monitors key environmental conditions of the crop.

Drying and curing of buds

Once the plants are cut, the process is not over. Drying and curing are essential to preserve the flavor, aroma and potency of the buds.

Drying:

• Hang the branches upside down in a dark, ventilated place with a temperature between 18 and 22 ºC (64 and 72 ºF).
• Relative humidity should be between 50% and 60%.
• The process lasts between 7 and 14 days, depending on the climate and the size of the buds.
• The buds are ready when the small branches crackle when breaking.

Cured:

• Store the dried buds in airtight glass jars (mason jar type).
• Open them once a day for the first 10-15 days to renew the air (this is called airing).
• Curing can take from 3 weeks to several months. The slower and more controlled, the better the final result.

Good drying and curing greatly improves the flavor, smoothes the smoke and stabilizes the cannabinoid and terpene profile.

More information on cannabis drying and curing

Common mistakes when growing autoflowering plants (and how to avoid them)

• Excessive watering: can choke the roots and cause fungus. Let the substrate dry out between waterings.
• Unnecessary transplants: the stress of transplantation can halt their development.
• Lack of light: limits growth and bud formation.
• Substrate heavily fertilized from the start: can burn young roots.
• Do not measure the pH of the water: it affects nutrient uptake. Keep pH between 6.0 and 6.5.

Frequently asked questions about growing autoflowering plants (FAQ)

Final tips for successful cultivation

• Select quality autoflowering seeds, from reliable banks, preferably with a good breeding work that guarantees stability, productivity and resistance. Choose genetics adapted to your objectives, be it high THC production, CBD content or cultivation in specific conditions.
• Keep a cultivation calendar with watering, fertilizing and observations.
• Perform a root flush (water only) at least 10 days before harvest, especially if mineral or high concentration fertilizers have been used. Although the cycle of the autos is short, a well programmed washing helps to eliminate the excess of salts accumulated in the substrate and improves notably the flavor, the aroma and the smoothness of the final bud.
• Do not over-handle plants, especially during flowering.
• Take photos and notes to learn from each crop.

Growing autoflowering marijuana can be as easy as it is rewarding, even for those who are just starting out in the world of cannabis. Thanks to their fast cycle, resistance and ease of management, these plants allow frequent and quality harvests with a minimum of complications. By following this step-by-step guide and avoiding the most common mistakes, you will be able to optimize each crop, whether indoors or outdoors, and enjoy your own autoflowering cannabis flowers, whether rich in THC or high in CBD. Much success and happy growing!

This content is for informational purposes only and is intended for adults in countries where cannabis cultivation is permitted. Find out about the cannabis cultivation regulations that apply in your region.

Bibliography on the cultivation of autoflowering plants

• Marijuana: cannabis horticulture. The bible of the indoor and outdoor medical grower by Jorge Cervantes (2006). Van Patten Publishing.
• The Cannabis Encyclopedia by Jorge Cervantes (2018). Van Patten Publishing.
• The Cannabis Grow Bible: The Definitive Guide to Growing Marijuana for Recreational and Medicinal Use by Greg Green (2017). Green Candy Press.
• Cannabis Grower’s Handbook: The Complete Guide to Marijuana and Hemp Cultivation by Ed Rosenthal (2020). Quick American.
• Revista Cáñamo, magazine specialized in cannabis cultivation. The number 1 of reference in Spain.
• Introduction to autoflowering cannabis cultivation by Jeff Lowenfels (2019). Melusina Editions.