This seasonal calendar shows when specific tasks in plant cultivation make sense: from indoor climate and light control to substrates, nutrient management and plant protection (IPM). The guide is legally neutral, aimed at an adult audience and applicable to aromatic plants, herbs & ornamental plants. Please always observe local legislation.
The indoor calendar is set up by default for a 12-month season, representing a continuous year-round cycle. Depending on your objectives, room climate and available setup, this timeframe can be flexibly adjusted – for example, to multiple shorter seasons per year (e.g. quarterly or semi-annually). This allows maintenance windows, cleaning/hygiene phases and optimisation cycles (light, climate, nutrient management) to be bundled in a planned manner without losing operational stability.
What do we at S&R mean by “Seasonal Grow Calendar”?
A seasonal calendar is a monthly roadmap for plant care. It helps plan time-critical tasks (e.g. repotting, lighting changes, climate adjustments, pest monitoring) – indoor all year round, outdoor depending on temperature, day length and weather windows.
Annual Overview (Indoor vs. Outdoor)
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Indoor: Year-round operation possible. Focus on stability (temperature, humidity, air exchange), light intensity (PPFD), photoperiod (timer), nutrient supply, hygiene and IPM.
- Outdoor (DACH region): Start window typically March–May (pre-cultivation/propagation), June–August growth emphasis, September–October maturation/harvest window depending on species, November–February rest, planning and equipment maintenance.
2026 | Monthly Grow Guide
January
Indoor: Stabilise climate (day/night differential 2–4 °C), humidity 55–65 % depending on species, light 16–18 h for vegetative growth. Hygiene reset: clean tent, fans, filters, trays; pest prevention (yellow sticky traps, adhesive traps, inspection routine).
Outdoor: Planning, seed/substrate/tool check, site analysis (wind, sun).
February
Indoor: Light check (PAR/PPFD measurement), test timers, adjust dimming to short days if needed. Define substrate strategy (soil/coco/hydro) and set up nutrient plan as a weekly routine.
Outdoor: Pre-cultivation of robust cold-tolerant species under LED or on the windowsill; prepare germination/propagation supplies.
March
Indoor: Repotting into fresh substrate, root zone 20–22 °C. IPM routine (visual inspection once per week).
Outdoor: Hardening off (gradually increase temperature/UV exposure), cold protection (fleece, mini greenhouse). Air circulation to prevent fungal infection.
April
Indoor: Airflow optimisation (intake at the bottom, exhaust at the top), check carbon filter. Photoperiod optionally set to 18/6 for growth.
Outdoor: Transplant cold-resistant herbs during frost-free nights, slug protection, mulch to reduce evaporation.
May
Indoor: Moderately increase nutrient curve, drain/EC/pH control (depending on system). Adjust climate control for warmer days (cooler intake air, mind dehumidification).
Outdoor: After the Ice Saints (mid-May), main transplanting. Set up supports/trellises, establish watering schedule.
June
Indoor: Adjust light intensity (PPFD) to plant height; leaf/canopy maintenance (remove old material, create air channels).
Outdoor: Growth emphasis – ensure adequate nutrient supply, water in the morning. Heat IPM: provide shade on hot days, check soil moisture.
July
Indoor: Summer peak: exhaust warm air, intake optionally from cooler rooms, CO₂ management only according to guidelines/manufacturer instructions.
Outdoor: Avoid drought stress (drippers, mulch), pest control 2×/week, have storm/hail protection ready.
August
Indoor: Day length (photoperiod) adjust according to target crop; keep humidity under control at night (dehumidifier/controller). Match nutrient plan to species & phase.
Outdoor: Maintenance month – tie, support, selectively thin out. Fungal prevention through air circulation.
September
Indoor: Plan harvest/maintenance window (drying/intermediate storage).
Outdoor: Depending on species, maturation window; weather monitoring (humidity/temperature), rain protection (covers) for sensitive varieties.
October
Indoor: Turnover maintenance: check filters/fans, prepare for season change.
Outdoor: Season wrap-up: equipment maintenance, soil care/compost, winter cover for beds.
November
Indoor: Inventory review: What went well? Back up sensor data (temp/RH/CO₂), document recipes. Light maintenance (cleaning, new modules if needed).
Outdoor: Planning 2027 (varieties/species, crop rotation, wind protection, water).
December
Indoor: Hygiene reset (deep clean), calibration (pH/EC meters), inventory (substrates, fertilisers, filter media).
Outdoor: Tool servicing, frost protection for pots/water lines.
Checklist – Year-Round Basics
- Climate: Temperature stable, humidity phase-adjusted, fresh air & negative pressure in the tent.
- Light: Match PPFD to the growth stage, regularly check timer reliability, check distance/hotspots.
- Substrates & nutrients: Choose your medium deliberately (soil/coco/hydro), measure pH/EC appropriately for your system, make watering reproducible.
- Hygiene & IPM: Clean environment, quarantine new additions, traps/monitoring, proactive care.
- Legal & safety: Observe local laws regarding plant care & equipment.
S&R | Legal Notice
This article does not constitute an incitement to illegal activities. Content is kept technical and factual and relates to plant care, indoor climate and horticulture in general.
Glossary | Seasonal Grow Calendar 2026
Temperature — Heat level in the growing environment/leaf zone; a stable day/night differential promotes vitality.
Humidity (rel.) — Water vapour content of the air in %; adjusted by phase for stress and fungal prevention.
Air exchange — Intake and exhaust air renew O₂/CO₂, remove heat/moisture; the basis for a stable climate.
Air circulation — Circulating air in the room/tent to prevent hotspots and damp pockets.
Negative pressure — Slight vacuum effect in the tent so that exhaust air is drawn through the filter in a controlled manner.
Carbon filter — Filters odours/particles from exhaust air; check throughput/maintenance regularly.
Light intensity (PPFD) — Photosynthetic Photon Flux Density (µmol/m²/s) at the canopy; controls photosynthesis performance.
PAR — Photosynthetically active radiation (400–700 nm), the spectral range usable by plants.
DLI — Daily Light Integral (mol/m²/day); daily light quantity = PPFD × lighting duration.
Photoperiod — Length of light/dark phase (e.g. 18/6 h); controlled by timer.
Timer — Switches light/ventilation reproducibly; the foundation of consistent photoperiods.
Nutrient supply — Planned delivery of macro/micronutrients per medium/phase.
pH — Acidity of nutrient solution/soil; affects nutrient availability.
EC — Electrical conductivity (mS/cm) as a proxy for nutrient concentration.
Drain — Runoff solution after watering; EC/pH testing reveals salt build-up/balance.
Substrate — Soil, coco, hydro (inert/water-based); determines watering as well as pH/EC management.
Hydroponics — Soilless cultivation in nutrient solution; high controllability, measurement discipline required.
Coco (Coir) — Fibrous medium with good aeration/water retention; keep pH/EC in check.
Soil — Buffered organic-mineral medium with microbiology; forgiving for beginners.
IPM (Integrated Pest Management) — Prevention, monitoring (traps/visual inspection), targeted, gentle measures.
Hygiene — Cleaning/disinfecting tent, tools, trays; avoid cross-contamination.
Hardening off — Gradually acclimatising young plants to outdoor conditions (UV/temperature/wind).
Repotting — Transferring to larger containers/fresh medium to promote root development.
Trellis — Supports/ties for stabilisation and better light distribution.
Mulch — Ground cover to reduce evaporation and temperature fluctuations.
VPD — Vapour Pressure Deficit; the relationship between temperature & RH, controls transpiration.
Dehumidifier — Device for lowering humidity, especially at night/with high plant density.
Fresh air — Cool, oxygen-rich intake air for climate stabilisation.
CO₂ management — Handling CO₂ levels according to guidelines/manufacturer specifications.
Pest monitoring — Visual inspection, yellow sticky traps, records; the basis for IPM decisions.
Fungal prevention — Air circulation, phase-adjusted RH, leaf/soil hygiene.
Watering schedule — Reproducible cycle depending on medium, pot size, climate.
Photon measurement — PAR/PPFD meters (quantum sensor) for objective light assessment.
Sensor calibration — Regular calibration of pH/EC meters & data loggers.
Seasonal window — Time periods during which outdoor measures are climatically sensible.
Storm/hail protection — Nets/covers to minimise damage.