Cannabis Grow Calendar 2026 (Outdoor + Indoor) – When to Germinate, Water, Feed and Harvest

IMPORTANT! If you need specific dates – what to do and when – go to this article: Lunar calendar for cannabis – exact days and timings!

Maximize your yield!

Growing cannabis isn’t only about good genetics and strong lights. The biggest difference in yield and quality often comes from timing — when you start, when you transplant, when you feed, and when you harvest.

That’s why many growers use a seasonal grow calendar (outdoor) or a step-by-step workflow (indoor). A good calendar helps avoid common mistakes like starting too early outdoors, overwatering during cold nights, moving plants outside too late, or harvesting too late in wet autumn conditions.

Below you’ll find a practical, clear guide: what to do and when, for both outdoor and indoor cannabis cultivation.

✅ Outdoor Cannabis Grow Calendar – Month by Month

Outdoor growing has a big advantage: sunlight is free. The downside is that you can’t control the weather, so planning the season properly matters a lot.

? MARCH – APRIL: Germination & Early Growth (Best Done Indoors)

In most European climates (including Poland), the outdoor season starts with indoor preparation. If you want strong plants for summer, starting earlier indoors makes a huge difference.

What to do in this stage:

• Germinate seeds (paper towel / starter plug / small pot)

• Start in a small container (light soil or coco)

• Keep seedlings growing steadily under light (LED/fluorescent)

• Water lightly — moist, not soaked

Common mistakes:

• overwatering (“muddy soil” = low oxygen = slow roots)

• weak light = stretchy, thin seedlings

• cold nights = slow growth and stress

Goal at this stage: strong roots, a thicker stem, healthy balanced growth.

? APRIL – JUNE: Hardening Off & Moving Plants Outdoors

Once temperatures rise, you can start thinking about outdoor transplanting. The most important thing is to avoid temperature shock and wind stress.

What to do:

• Harden plants off (outside for a few hours daily)

• Transplant into bigger pots or into the ground

• Choose the right spot: sun + airflow + no standing moisture

• Start light veg feeding (N-based), no heavy doses

Outdoor watering basics:

Outdoor problems are usually caused by watering mistakes:

• overwatering (cold nights + wet soil)

• underwatering (heat + small pots)

Simple rule:
✅ water when the pot feels light and topsoil is dry
❌ don’t water “because it’s watering day”

? JUNE – AUGUST: Fast Growth, Training & Plant Shaping

This is where you build your final yield. Your plant grows size and structure, and you can shape it for better production.

What’s useful here:

• LST (low stress training) – bend branches to create more tops

• Topping (optional) – encourages more branching

• Improve airflow (especially after rain)

• Feed regularly for growth — with control and balance

Big yield comes from:

• strong sunlight exposure

• large, healthy root mass

• correct watering rhythm

• sensible feeding (avoid nutrient burn)

✂️ JULY – AUGUST: Pruning, Cleanup & Mold Prevention

When plants get big and bushy, airflow drops and disease pressure rises — especially during humid nights.

What to do:

• remove some leaves blocking airflow (don’t overdo it)

• keep the center from becoming too dense and damp

• clean the lower weak growth

• watch closely for pests and mold

Outdoor isn’t sterile. Prevention is easier than saving the grow later.

? SEPTEMBER – NOVEMBER: Flowering & Harvest

Outdoor flowering can be amazing — but also risky. The key is harvesting at the right moment: not too early, not too late.

What to do:

• switch feeding to bloom nutrients (PK-focused)

• monitor rain and humidity

• protect plants from constant wetness if possible

• check trichomes (loupe) and bud condition

Biggest outdoor issue: mold

Once cold and wet weather arrives, mold can destroy buds fast. That’s why:

• harvesting slightly early is often better than losing everything

• airflow and spacing between buds matter a lot

✅ Indoor Cannabis Grow Calendar (Grow Tent / Grow Box)

Indoor gives you one major advantage: you can run a full cycle any time of the year. The key is a clean workflow:

Typical indoor timeline:

• Germination / seedling: 1–7 days

• Vegetative stage: 2–6 weeks (depending on your plan)

• Flowering: usually 8–10 weeks (strain dependent)

• Flush / finishing: 7–14 days (optional)

? Indoor Start – Germination & First Days

The #1 beginner mistake is overwatering early on.

What the plant needs at the start:

• moisture, but not soaked soil

• light growing medium

• lots of oxygen for roots

• gentle light + stable temperature

? Vegetative Stage – Building Roots and Structure

You build yield in veg, even before flowers appear.

What to do in veg:

• transplant gradually into bigger pots

• shape the plant using LST / topping (optional)

• keep stable climate (temperature + humidity)

• feed smart: slightly less is safer than burning the plant

? Flowering – Bud Quality and Final Results

Flowering is where mistakes show up fast.

What matters most in bloom:

• consistent watering (avoid waterlogging)

• strong light and good coverage

• airflow + extraction fan

• correct PK and micros (without overfeeding)

If leaves turn very dark and claw downward, it’s often a sign of too much nitrogen or overfeeding.

✂️ Indoor Harvest – When to Cut?

Don’t rely only on “days on a chart”. Harvest based on what you see.

Most growers harvest when:

• most pistils are mature

• buds are dense and fully developed

• trichomes show the right maturity (loupe)

After harvest, quality still depends on:
✅ slow drying (no rushing)
✅ proper curing in jars (this is where aroma really develops)

? Quick Grow Timing Guide – When to Do What?

✅ When to germinate / start?

• whenever you want to start a cycle (outdoor: spring, indoor: year-round)

• stable warmth + no overwatering = success

✅ When to transplant?

• when roots fill the pot quickly

• when soil dries out much faster than before

✅ When to feed?

• lightly from week 2–3 (depends on your medium)

• stronger during fast veg growth

• switch to bloom feeding when flowering begins

✅ When to water?

• only when the pot feels lighter

• don’t follow “fixed watering days” — follow the soil and plant

✅ When to harvest?

• outdoor: usually September–November (strain + weather dependent)

• indoor: often after 8–10 weeks of bloom, but check trichomes

❓ FAQ – Outdoor & Indoor Cannabis Grow Calendar

Does outdoor growing make sense in Europe/Poland?

Yes, but genetics and timing matter. The biggest risk is humidity and mold in autumn.

Is indoor easier than outdoor?

It’s more predictable, but you must control temperature, humidity and watering correctly.

What increases yield the most?

Stability: strong roots, good light, correct watering, and balanced feeding.

What is the most common mistake?

Overwatering and overfeeding. These ruin more grows than “missing supplements”.

✅ Summary

A good cannabis grow (outdoor or indoor) is built on:

• strong start and healthy roots,

• steady vegetative growth,

• correct watering rhythm,

• smart feeding,

• harvesting at the right time.