The outdoor cannabis season is eagerly awaited each year. The most important questions—"When to plant outdoor cannabis?", "When to harvest?" and "What is the cannabis growing calendar?"—return every spring and autumn. The answer depends on your frost zone, day length, and chosen genetics. Here you'll find a complete outdoor cannabis cultivation calendar for European countries and regions, from the last spring frost to safe harvest dates, with practical advice.
Frost Zones in Europe — Last and First Frost Dates
Europe is a climatic mosaic:
The North (Scandinavia, Baltic countries) is characterized by the shortest summers and high risk of night frosts.
Central Europe (Poland, Germany, Czechia) has moderate springs and autumns with frosts possible until mid-May and again from mid-September.
Southern Europe (France, Italy, Spain, Greece) offers the longest outdoor growing season, almost free of frosts.
The last spring frost—when it's safe to plant outdoors—depends on the region. The first autumn frost marks the limit for harvesting late strains. Your local microclimate may shift these dates by a week or two.
Table: Frost Dates in Europe
| Region | Last spring frost | First autumn frost |
|---|---|---|
| Northern Europe | May 20 – June 10 | September 1 – September 20 |
| Central Europe | April 10 – May 10 | September 20 – October 20 |
| Southern Europe | March 1 – April 1 | October 20 – November 30 |
Photoperiod and Latitude
Photoperiod—that is, day length—controls flowering in photoperiod cannabis strains. When the day shortens below around 14–15 hours, the plant starts to flower. The further north, the longer the days in summer, so flowering begins later. In Central Europe, days below 15 hours start from mid-July; in the south, earlier. Automatic strains ("autoflowering") do not react to day length—they flower about 2–4 weeks after sprouting, regardless of light.
Optimal Planting Dates by Region
Safe planting starts after the last frost. Too early—risk of damage; too late—smaller yields. Before moving plants outside, harden them for at least a week. Automatic strains can be sown outdoors earlier, as soon as soil temperature exceeds 12–15°C.
Table: Outdoor Cannabis Planting Calendar in Europe
| Region | Indoor seed sowing | Planting after hardening |
|---|---|---|
| Northern Europe | late May – early June | June 5–15 |
| Central Europe | April – mid-May | May 10–25 |
| Southern Europe | March – early April | April 1–15 |
Harvest Dates: Photoperiod vs Autoflowering
Photoperiod strains:
Early: late August – mid-September
Medium: mid-September – early October
Late: second half of October – first frost
Autoflowering:
Sown in May: harvest in late July or early August
Sown in June: harvest in late August or early September
Sown in July: harvest in late September to early October
Table: Harvest Dates by Region
| Region | Early photoperiod | Medium photo. | Late photo. | Autoflowering |
|---|---|---|---|---|
| North | Sept 1–15 | Sept 15–Oct 1 | Oct 10–25 | July 20–Sept 5 |
| Central | Aug 25–Sept 10 | Sept 10–30 | Oct 1–20 | July 20–Sept 5 |
| South | Aug 10–25 | Sept 1–20 | Sept 20–Nov 10 | July 20–Aug 20 |
Weather Contingency Plan
Cold nights: Use garden fleece or move potted plants under plastic tunnels.
Heavy rains: Ensure good drainage, remove lower leaves, maintain spacing between plants.
Heat waves: Water in the morning and evening, use shading, add hydrogel to the soil.
Table: Calendar Adjustments According to Microclimate
| Parameter | Calendar effect | Date adjustment |
|---|---|---|
| South-facing patio | Warmer, earlier | Plant/harvest -7 days |
| North-facing | Cooler, more humid | Plant/harvest +7 days |
| Near water | Mild temp. variation | Plant/harvest -7 days |
| Open field | Frost/wind risk | Plant/harvest +7–14 days |
FAQ
When is the earliest to plant outdoor cannabis after frost?
The earliest is after the last frost—early June in northern Europe, mid-May in central, as early as April in the south. Soil temperature should be at least 12–15°C.
How does day length affect flowering in Poland?
Photoperiod strains start flowering when the day shortens below 15 hours (usually mid-July). Autoflowering strains are not affected by day length.
When to harvest autoflowering vs photoperiod plants in northern/southern EU?
Photoperiod: mid-August to first frost, depending on type. Autoflowering: 7–11 weeks after sowing—earlier in warmer regions.
What to do if frost is forecast in September?
Protect plants with fleece, move pots to warmer places, reduce watering, and trim leaves to accelerate harvest.
Can you speed up or delay harvest without losing quality?
Harvest can be sped up by reducing water and increasing potassium/phosphorus, but doing so too quickly lowers quality. Delaying increases risk of mold and frost damage—follow forecasts and don’t wait too long.
Summary
Choose planting date by frost zone.
Day length determines flowering in photoperiod strains.
Adjust dates according to your local microclimate and weather.
Keep a grow diary—optimize for next seasons.
Plan harvest flexibly for chosen genetics and climatic conditions.
