Growing Cannabis: Basics, Care and the Most Common Mistakes

Since the Consumer Cannabis Act (KCanG) came into force in April 2024, adults in Germany have been allowed to grow up to three cannabis plants for personal use. What sounds simple on paper requires a solid basic understanding in practice – because cannabis is a demanding plant.

In this article you will learn what really matters when growing cannabis: from the most important growth factors to typical beginner mistakes to general notes on harvesting and drying. No hocus-pocus, no half-knowledge – just well-founded basics that let you start the 2026 growing season well informed.

Legal Framework: What Is Allowed?

Before we get to the plant itself, a quick look at the rules. The KCanG allows adults:

• A maximum of three cannabis plants at a time at the place of residence or usual place of stay
• Possession of up to 25 grams of cannabis outside your own home
• Up to 50 grams of dried cannabis in the private sphere
• Seeds may be legally acquired and possessed in Germany

Important: The cultivation must be secured so that minors and unauthorized third parties have no access. An open balcony without a privacy screen is therefore not a good idea.

Note: Laws can change. Always find out about the current status before growing.

Understanding the Cannabis Plant

Cannabis is an annual plant with a clearly defined life cycle. Anyone who wants to grow successfully should know the three central phases:

Germination and Seedling Phase (1–3 weeks)

It all starts with the seed. In the germination phase, the taproot (the first main root growing downward) forms, from which the first cotyledons develop within a few days. Seedlings are sensitive – they need even moisture, moderate warmth (20–25 °C) and gentle light.

Typical mistake: Too much water in this phase. The roots are still tiny and can quickly rot in waterlogged conditions.

Vegetative Phase (3–8 weeks)

In the vegetative phase, the plant grows in height and forms leaves, branches and a strong root system. This is where it is decided how vigorous and resilient it will be later.

In this phase the plant needs:

• 16–20 hours of light per day (for indoor cultivation)
• Nitrogen-focused nutrient supply for leaf growth
• Good air circulation to prevent mold formation

Flowering Phase (6–12 weeks)

In photoperiodic strains, flowering is triggered by shortening the light duration to about 12 hours. Autoflowering strains bloom independently of the light cycle – an advantage for beginners.

During flowering, the nutrient requirement shifts significantly: less nitrogen, more phosphorus and potassium. The plant now forms flowers, trichomes and resins.

The Five Decisive Growth Factors

1. Light

Light is the most important factor in growing cannabis. Outdoors, the sun provides everything that is needed – provided the location gets at least 6–8 hours of direct sunlight.

Indoor growers rely on LED or full-spectrum lamps. As a guideline, around 150–300 watts (LED) per plant apply – depending on the growth phase and cultivation area. The rule of thumb: The more high-quality light the plant receives, the better its structure and flowers develop.

Caution: Too much heat from incorrectly positioned lamps is one of the most common causes of light burn – recognizable by yellowed, bleached leaf tips.

2. Watering

Cannabis needs even but not excessive watering. The top layer of substrate should dry out slightly between waterings. Waterlogging is the most common cause of root problems.

Rule of thumb: Better to water thoroughly once than constantly a little.

A well-draining substrate with a perlite content helps to drain off excess water. Anyone watering with tap water should check the pH value – ideally it is between 6.0 and 7.0 in soil (slightly lower for coco substrate: 5.5–6.5).

3. Substrate and Soil

The right substrate is the foundation for healthy growth. High-quality, pre-fertilized potting soil works well for beginners. Advanced growers mix their own substrates with coco, perlite and worm compost.

What matters:

• Loose structure for good aeration of the roots
• Sufficient drainage (holes in the pot are a must)
• Neutral to slightly acidic pH value (6.0–6.8)
• Sufficient pot size: 10–20 liters for the final pot, depending on the strain and available space

4. Temperature and Humidity

Cannabis thrives best at temperatures between 20 and 28 °C during the light phase. At night, the temperature should not fall below 15 °C.

The optimal humidity changes over the course of the life cycle:

• Seedling: 65–70 %
• Vegetation: 50–60 %
• Flowering: 40–50 %
• Late flowering: 30–40 %

During flowering, humidity that is too high is dangerous: mold (especially Botrytis) can destroy the entire harvest.

5. Nutrients

Cannabis has a different nutrient requirement in every growth phase. The three main nutrients (NPK) – nitrogen, phosphorus and potassium – should be supplied in the right balance.

• Vegetation: High nitrogen requirement (N), moderate phosphorus (P) and potassium (K)
• Flowering: Less nitrogen, significantly more phosphorus and potassium
• Micronutrients such as calcium, magnesium and iron are also important

Typical mistake: Over-fertilization. With cannabis, less is often more. Yellow leaf tips and burnt leaf edges are classic signs of nutrient excess.

Common Beginner Mistakes When Growing Cannabis

You learn a lot about growing through experience. But some mistakes come up so regularly that it's worth knowing them beforehand:

1. Overwatering
The most common mistake of all. Cannabis likes moist, not wet soil. If the leaves hang down limply and the soil is permanently moist, the plant is getting too much water.

2. Wrong pH value
Even with sufficient fertilization, nutrients cannot be absorbed if the pH value in the substrate is wrong. Invest in an inexpensive pH meter – it will save you a lot of problems.

3. Too much fertilizer, too early
Young plants need hardly any additional nutrients. Pre-fertilized soil is usually completely sufficient for the first 3–4 weeks.

4. Poor ventilation
Stagnant air encourages mold and pests. A light draft also strengthens the stems and promotes growth.

5. Impatience at harvest
Many beginners harvest too early. The trichomes (the small resin glands on the flowers) give the best indication of the right time: Clear trichomes mean: too early. Milky-cloudy trichomes indicate the start of the harvest window. When the first trichomes turn amber (approx. 20–30 %), the ideal time for most strains has been reached.

Recognizing Typical Problems

The plant communicates – you just have to look:

• Yellow leaves from below: Often a sign of nitrogen deficiency, especially normal during flowering (the plant shifts nutrients into the flowers)
• Yellow leaves from above / leaf tips: Can indicate light burn, nutrient excess or pH problems
• Brown, dry leaf edges: Often nutrient burn (over-fertilization) or humidity that is too low
• Drooping leaves with moist soil: Overwatering – water less, check drainage
• White dots on leaves: Possible infestation by spider mites or powdery mildew

When in doubt: change less, observe closely and adjust only one variable at a time.

Harvest, Drying and Storage – an Overview

Once the flowering phase is complete, harvesting, drying and curing follow. Without claiming to be a complete guide, here are the most important principles:

Harvest: The harvest time significantly influences the end product. A pocket microscope helps to assess the trichomes.

Drying: Dry slowly at 18–22 °C and about 55–60 % humidity. Drying too quickly impairs flavor and quality. Drying usually takes 7–14 days.

Storage: After drying, curing follows in airtight jars. During the first two weeks, the jars are opened daily for a few minutes (“burping”). For optimal results, curing should last at least four weeks – experienced growers let it mature for up to eight weeks. This significantly improves aroma, flavor and tolerability.

Outdoor vs. Indoor: Which Suits You Better?

Outdoor:

• Lower costs (the sun is free)
• Natural growth, more robust plants
• Dependent on weather, climate and season
• Growing season in Germany: approx. May to October

Indoor:

• Full control over light, temperature and humidity
• Possible all year round
• Higher investment (lamps, ventilation, electricity)
• More discreet
• Activated carbon filter for the exhaust air necessary (cannabis smells intense during flowering)

For absolute beginners with a limited budget, an outdoor grow on the balcony (with a privacy screen) can be the easier start. Those who want more control opt for an indoor setup.

The Right Time: When Does the 2026 Growing Season Start?

For outdoor growers in Germany, the schedule looks like this:

• 🌱 March / April – germinate seeds and pre-grow seedlings indoors
• ☀️ Mid-May – plant out after the Ice Saints (no more frost risk)
• 🌿 June – August – vegetative and early flowering phase
• 🍂 September / October – harvest (depending on strain)

Those who use autoflowering strains can, thanks to the shorter life cycle, also start later in the year and still harvest before the first frost.

Frequently Asked Questions

Is growing cannabis legal in Germany?

Yes, since April 2024 the KCanG has allowed adults to grow up to three cannabis plants for personal use at their place of residence. The plants must be protected from access by minors and third parties.

When should I start growing in 2026?

Indoors you can start at any time. For outdoor cultivation, March/April is the ideal time for pre-growing. Planting out takes place after the Ice Saints from mid-May.

How often do I have to water my cannabis plant?

That depends on pot size, substrate, temperature and plant phase. Basically: only water when the top layer of soil (2–3 cm) is dry. Overwatering is the most common beginner mistake.

What do yellow leaves on my cannabis plant mean?

This can have various causes: nitrogen deficiency, pH value problems, overwatering or light burn. It is important to consider the position of the yellow leaves and the overall condition of the plant in order to narrow down the cause.

Which is better – indoor or outdoor?

That depends on your budget and your possibilities. Outdoor is cheaper and more natural, but weather-dependent. Indoor gives you full control but costs more in purchase and electricity.

What is the difference between photoperiodic and autoflowering strains?

Photoperiodic strains begin to flower when the light duration drops to about 12 hours. Autoflowering strains flower automatically after a certain time, independent of the light cycle – ideal for beginners.

Why are activated carbon filters relevant for enjoyment?

A good filter reduces pollutants and ensures a more pleasant experience. Especially if you grow your own and value quality, a high-quality activated carbon filter is part of the basic equipment. More on this in our article about activated carbon filters.

How long does it take from germination to harvest?

Depending on the strain and method, between 3 and 7 months. Autoflowering strains are the fastest at approx. 10–14 weeks. Photoperiodic strains usually need 4–6 months.

---

Images: Unsplash

Conclusion

Growing cannabis is not rocket science – but it's not a sure thing either. Anyone who understands the basics, is patient and pays attention to the signals of their plant can achieve good results with relatively simple means.

The most important takeaways:

• Less is more – with water and fertilizer
• Light and air circulation are the underestimated game changers
• Observe instead of correcting blindly – the plant shows you what it needs
• Patience at harvest pays off

And when everything is dried and finished at the end, the right filter makes the difference. Find out here what activated carbon filters really do.