Why isn’t my cannabis plant growing?

If you’re wondering why your cannabis plant isn’t growing, you’re not alone. It’s one of the most common problems, especially when growing outdoors, when factors such as the weather, growing medium or watering aren’t quite right. In this article, we explain the real causes of slow growth in cannabis, for both autoflowering and photoperiod plants, and how to solve it step by step.

The 7 reasons why your cannabis plant isn’t growing outdoors

1. Lack of sunlight (the most common)

Cannabis needs many hours of light to develop properly. This is the main reason why your plant may not be growing properly. Typical problem:

• Less than 5–6 hours of direct sunlight per day
• Partially shaded location

Result:

• Slow-growing cannabis plant outdoors
• Weak, spindly stems

Solution:

• Location with at least 6–8 hours of direct sunlight
• South-facing (ideal in Spain)

2. Poor or compacted growing medium

A very common mistake is using poor-quality or overly compacted soil.

Problem:

• Lack of oxygenation in roots
• Poor drainage

Result:

• Small plant
• Limited root development

Solution:

• Use an aerated growing medium (mixed with perlite or coconut fibre)
• Avoid clay soils

3. Incorrect watering (too much or too little)

Poor watering management is one of the main reasons why cannabis fails to grow.

Too much:

• Root suffocation
• Fungal growth

Not enough water:

• Water stress
• Stunted growth

Result:

• Cannabis fails to grow outdoors → solution: adjust watering

Solution:

• Water only when the top layer is dry
• Avoid waterlogging

4. Inappropriate temperatures

The climate directly influences growth. So when you wonder why your plant isn’t growing, the climate could be directly affecting its development.

Problems:

• Cold (start of the season)
• Extreme heat

Result:

• Slow or stunted growth

Particularly important for:

• Autoflowering seeds → short cycle, more sensitive
• Photoperiod seeds → more resilient, but also affected

Solution:

• Plant at the right time (spring)
• Protect from night-time cold

5. Seed genetics

Not all seeds grow the same.

Problem:

• Weak genetics
• Low-quality seeds

Result:

• Small cannabis plant outdoors

Key difference:

• Autoflowering → faster but limited growth
• Photoperiod-dependent → larger size and development if given time

Solution:

• Choose quality cannabis seed banks such as Buddha Seeds (this directly impacts the result)

6. Pests or diseases

Sometimes the problem isn’t visible at first glance.

Common pests:

• Spider mites
• Thrips
• Aphids

Result:

• Stunted plant
• Damaged leaves

Solution:

• Check the underside of the leaves
• Apply preventative treatments

7. Lack of nutrients

If the plant doesn’t have enough food, it won’t grow.

Problem:

• Nitrogen deficiency during growth

Result:

• Yellow leaves
• Slow growth

Typical search:

• “why isn’t my plant growing after germination”

Solution:

• Balanced growth fertiliser
• Do not over-fertilise

Autoflowering vs photoperiod-dependent outdoors

This has a major influence on growth:

Autoflowering

• Fast cycle (60–90 days)
• Smaller size
• More sensitive to mistakes

If they don’t grow quickly at the start → difficult to recover

Photoperiod-dependent

• Prolonged growth
• Larger size and yield
• Greater margin for recovery

Ideal for outdoors if you’re looking for large plants

Reasons why your plant isn’t growing outdoors

If your plant isn’t growing outdoors, check:

• Sunlight
• Substrate
• Watering
• Temperature
• Genetics
• Pests
• Nutrients

In 90% of cases, the problem lies in one of these areas.

Buddha Seeds varieties with vigorous outdoor growth

If you want to avoid problems from the start, choosing good genetics is key. These varieties stand out for their vigour outdoors:

Autoflowers

• White Dwarf Auto
• Very hardy, ideal for beginners
• Red Dwarf Auto
• Good yield and quick adaptation
• Deimos Auto
• Very stable and productive outdoors

Photo-dependent

• Kraken
• Stands out for its vigorous growth outdoors, good structure and ability to develop strongly during the vegetative phase.
• Quasar
• A very interesting strain for outdoor growing if you’re looking for a plant with strong growth, solid structure and good development potential.