Caring for 4-Week-Old Autoflower Cannabis Plants

Caring for 4 week old autoflower cannabis plants ensures their overall health, development, and, eventually, their potency and yield. In this comprehensive guide, we’ll dive into the importance of proper care, covering topics such as growth stages, watering, feeding, lighting, temperature, humidity, pruning, training techniques, and potential challenges. With a pinch of humor and years…

Caring for 4-Week-Old Autoflower Cannabis Plants

Growth Stage at 4 Weeks

At the 4-week mark, your autoflower cannabis plants will transition from vegetative to the flowering stage.

This is an exciting time as the plants develop their distinctive buds and aromas.

However, it’s also a critical period for the plants, requiring specific care and attention to ensure healthy growth and maximum yield.

Growth Stage at 4 Weeks

Understanding the Transition to Flowering

Autoflower cannabis plants differ from photoperiod strains in that they begin flowering automatically, regardless of the light schedule.

That is due to their genetic background, which includes Cannabis ruderalis, a hardy species adapted to grow in harsh environments with short summers.

Autoflowering strains typically have an average seed-to-harvest cycle of 8 to 12 weeks, making them an excellent option for growers seeking a quick turnaround.


When it comes to watering your 4-week-old autoflower cannabis plants, there are a few guidelines to follow:

  • The water pH should be between 6 and 6.5 to ensure proper nutrient absorption.
  • At this stage, water your plants with 1 liter every 24 hours or 1.5 liters daily to keep the root zone moist without overwatering.
  • Be sure to use dark pots to prevent light from reaching the roots, which can lead to algae growth and other issues.

Feeding and Nutrients

Feeding your autoflower cannabis plants the right nutrients is crucial for their development.

At 4 weeks old, your plants will require a balance of nutrients, including:

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)

A good rule of thumb is to use a 2-1-2 ratio (N-P-K) for the vegetative stage and transition to a 1-2-3 ratio during flowering.

Additionally, consider supplementing with Cal-Mag to promote healthy growth and bud development.


The ideal lighting conditions for 4-week-old autoflower cannabis plants include the following:

  • light spectrum of 4000K to 5000K for the vegetative stage, shifting from 2700K to 3000K during flowering.
  • Light intensity should be between 400 to 700 μmol m-2 s-1.
  • Maintain a lighting distance of 70 cm (27.5 inches) from the canopy during the vegetative stage, reducing it to 45 cm (18 inches) during flowering.

Temperature and Humidity

Maintaining optimal temperature and humidity levels is essential for your 4-week-old autoflower cannabis plants. Aim for:

  • Temperature: 20°C to 24°C (68°F to 75°F)
  • Humidity: 50% during the vegetative stage, dropping to 40% during flowering

Use a hygrometer to monitor humidity levels and adjust as necessary.

Temperature and Humidity

Pruning and Training Techniques

Pruning and training your autoflower cannabis plants can help improve airflow, light penetration, and overall yield.

Here are some techniques to consider at the 4-week stage:

Low-Stress Training (LST)

Low-stress training (LST) involves gently bending and tying down the branches of your cannabis plants to create an even canopy and expose more bud sites to light.

This technique is highly effective for autoflower plants, encouraging horizontal growth without stressing the plant.

Benefits of LST for 4-week-old autoflower cannabis plants include:

  • Increased light penetration to lower bud sites
  • Improved airflow, reducing the risk of mold and pests
  • Enhanced yield potential

Other Training Techniques

Some other training techniques suitable for 4-week-old autoflower cannabis plants include:

  1. Topping: Removing the top growth tip of the main stem to encourage the development of multiple colas. However, this can be stressful for autoflower plants and is best suited for those with extended vegetative periods.
  2. Fimming: A less invasive alternative to topping, fimming involves cutting only a portion of the growth tip, promoting bushier growth without causing significant stress to the plant.

Potential Challenges

Growing 4-week-old autoflower cannabis plants can present a few challenges.

We’ll discuss common issues and offer solutions to help you quickly navigate this stage.

Pests and Diseases

Some common pests and diseases that may affect 4-week-old autoflower cannabis plants include:

To prevent and treat these issues, maintain a clean growing environment, ensure proper airflow, and use organic pest control methods such as neem oil or beneficial insects.

Other Potential Issues

Some other potential issues when caring for 4-week-old autoflower cannabis plants include:

  • Overwatering or underwatering
  • Nutrient deficiencies or toxicities
  • Light stress or burn

To address these issues, monitor your watering schedule, adjust nutrient levels, and ensure proper lighting conditions.

Tips for a Successful Autoflower Grow

To maximize the yield and potency of your 4-week-old autoflower cannabis plants, consider the following tips:

  • Monitor and adjust pH levels regularly
  • Use high-quality soil or coco coir as a growing medium
  • Rotate your plants to ensure even light exposure
  • Be patient and observant, making adjustments as needed
Tips for a Successful Autoflower Grow


Why is my autoflower small after 4 weeks?

A small autoflower plant after four weeks could be due to several factors, such as inadequate lighting, nutrient deficiencies, or genetics.

How many weeks does it take for Autoflowers to flower?

Autoflowers typically begin flowering between weeks 2 and 4, with most strains finishing their seed-to-harvest cycle in 8 to 12 weeks.

What should my autoflower look like at 3 weeks?

At three weeks, your autoflower plant should be around 15 cm (6 inches) tall, with several sets of leaves and possibly some early pre-flowers or pistils.

What are the first signs of autoflower flowering?

The first signs of autoflower flowering include the appearance of white hairs (pistils) at the nodes and the development of small, tight bud sites.

What week do Autoflowers stop growing?

Autoflowers typically stop their vertical growth during weeks 4 to 6 as they shift their energy towards flowering and bud development.

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