Germination Calendar
Plan your grow around a real timeline. Start with seeds or clones today and see every milestone — transplant, flip, flower sites, stop-feeding, harvest window — as calendar dates. Or work backwards from a target harvest date to know exactly when to start. Covers seeds and clones, photos and autos, every training method, and perpetual stagger planning for continuous harvest.
Build your grow calendar
From the seed description. Most strains 7–12 weeks.
Date seeds go in medium, or clones are cut.
Default is set by training method. Override if you know your exact veg plan.
About this mode
—
Pick a mode above.
Common germination and planning mistakes
- Trusting breeder weeks as gospel. Breeder flower times are averages — individual phenotypes of the same strain often finish 1–2 weeks later. Always confirm with trichomes, not the calendar.
- Forgetting to count seedling time. It's 2–3 weeks from germination to a transplant-ready seedling. First-time growers frequently forget to add this to their timeline and are surprised when "12 week grow" takes 17 weeks.
- Flipping too early under SCROG. Screen should be 70–80% filled before you flip. Rushing the flip with an underfilled net wastes the entire SCROG setup — you end up with a sparse canopy and sub-optimal yields.
- Not accounting for post-harvest. Harvest is not the end — drying takes 7–14 days, curing takes 2–6 weeks. Plan total time to smoke-ready, not just to chop.
Harvest window
—
Peak: —
—
Full timeline
Key milestones
| Date | Milestone |
|---|---|
| — | |
Plan from first seed to harvest day
Choose forward or backward planning
Forward: enter your start date and see all the milestones from there. Best for most growers who are starting a grow now or planning to start shortly. Backward: enter a target harvest date and the tool works out when you need to start. Best for event-driven timing — planning to have flower ready before a holiday, trip, or scheduled event. Both modes produce identical milestone lists; only the direction of calculation changes.
Set strain, source, training method, and breeder weeks
Pick seeds vs clones (clones skip the 3-week germination + seedling window entirely). Pick strain type — sativa and indica have different flower-time variance, and autos skip the flip entirely. Training method sets the recommended veg duration: SOG is 1–3 weeks, SCROG is 6–10 weeks. Breeder weeks from the seed description sets the flower phase — this is the biggest variable. Pro mode lets you override veg duration if you have a specific plan.
Read the timeline and milestone table
The tool outputs a color-coded phase timeline (each phase is a colored bar showing start → end date and duration in days) plus a milestone table with every key action. Critical dates to circle: Flip to 12/12 (for photos), Flower sites visible (start flower feeding), Stop nutrients (10 days before harvest window), Harvest window opens, and Peak harvest. The milestone table is what you'd print and stick to your tent.
Use Pro mode for perpetual stagger planning
If you want continuous harvest rather than one big chop every 4–5 months, turn on Pro mode and set batch count + stagger interval. The tool shows all start dates and harvest windows for each batch. Classic perpetual setup: 2 or 3 batches staggered 4–6 weeks apart in a 2-tent or room-with-veg-tent setup. See the batch table to verify harvests fall when you want them — adjust stagger weeks until the harvest dates fit your schedule.
Clone timelines vs seed timelines
Taking clones from a mother plant saves 3–4 weeks vs starting from seed (germination + seedling phases). The tool accounts for this — clone timelines start directly at veg. One nuance: the 10–14 day clone rooting period isn't a "growing phase" but it's real time. If you're taking clones from scratch today, add 10–14 days to the shown start date before clones can count as "veg start." If you already have rooted clones ready to go, use today as your start date.
Why the calendar says "confirm with trichomes"
Breeder flower times are averages. The same strain from the same breeder can finish 1–3 weeks apart across different phenotypes of the same seed batch. Temperature, humidity, VPD, and stress levels all affect finish time. The calendar's harvest window is based on typical phenotype behavior; actual readiness is confirmed with a jeweler's loupe or USB microscope. Use the Harvest Window Planner when you're within 2 weeks of the calendar window to confirm actual readiness by trichome state.
Lifecycle phases, training method timing, and why breeder weeks drift
Cannabis grows from seed to harvest through five distinct biological phases. Each phase has its own light requirements, nutrition profile, environmental targets, and duration range. The calendar tool chains these phases together; understanding what's happening biologically in each phase explains why the durations are what they are and where real-world timing diverges from the calendar. The Growing Overview covers the basics; this section covers the phase-specific science behind the timing math.
3–7d
Germination
Seed absorbs water, activates stored enzymes, and sends a taproot downward. Light not yet needed. Temperature 70–77°F optimal. Most viable seeds germ in 3–5 days.
14–21d
Seedling
Cotyledons open, then first true leaves appear. Chlorophyll production begins. Root system still small — no heavy feeding. 18/6 light, gentle environment.
2–10wks
Vegetative
Rapid leaf and stem growth. Node spacing, canopy width, and training response all happen here. Duration is the most grower-controlled variable in the whole lifecycle.
7–84d
Flower
12/12 light triggers photoperiod strains. Bud sites appear, swell, fill over 7–12 weeks. Trichome development is the actual measure of readiness — not the calendar.
Why veg duration is the most impactful decision you make
Flower duration is largely set by genetics. Germination and seedling are roughly fixed. But veg duration is entirely in the grower's hands, and it determines final plant size, yield potential, and — in SCROG especially — whether the grow is successful or frustrating. The tool's default veg times by training method:
| Method | Typical veg | Why this duration |
|---|---|---|
| SOG | 1–3 weeks | Many small plants, minimal training, flip while compact. Speed is the strategy — maximize harvest cycles per year. |
| LST | 3–6 weeks | Need time to develop branches wide enough to bend and tie. Flip when horizontal canopy coverage is achieved. |
| Untrained | 4–6 weeks | Standard growth time for a plant to reach a height where it will fill the tent appropriately by end of flower. |
| Topped / FIM | 5–7 weeks | Recovery after topping takes 7–10 days before nodes resume growth. Need extra time for multiple tops to develop. |
| SCROG | 6–10 weeks | Screen must be 70–80% filled before flip. Under-filling wastes the screen; over-growing creates an overly dense canopy that's hard to manage in flower. |
Why photoperiod breeder weeks drift in practice
Breeders report flower times under optimized lab-like conditions — dialed temperature, VPD, nutrition, and genetics. Real-world grows drift for several reasons:
Phenotype variance. Even within a single strain, individual plants from different seeds can finish 1–2 weeks apart. This is normal genetic variation. Clones of the same mother are more consistent; seed-grown plants will always show some variance.
Temperature effects. Cooler temperatures slow metabolic rate and extend flower time. A grow room running 68°F in late flower will finish noticeably later than one running 75°F. The tool uses typical multipliers (indica ×0.95, hybrid ×1.0, sativa ×1.1) — these are statistical averages, not guarantees.
Sativa drift is real. Sativa-dominant strains are notorious for exceeding breeder-stated flower times. The sativa multiplier in the tool caps at ×1.25 for maximum estimate, but some pure sativas can push 16+ weeks from flip. If you're growing a landrace or true sativa, assume the calendar's estimate is optimistic and check trichomes starting at week 10.
Autoflowers: no flip, compressed lifecycle
Autoflowering varieties contain Cannabis ruderalis genetics, which flower based on age rather than photoperiod. They begin pre-flowering automatically at roughly 3–5 weeks from sprout regardless of light schedule. Key differences vs photoperiod:
No discrete flip event. No transition phase. Total lifecycle from sprout is compressed to 8–12 weeks (advertised), often 10–14 weeks actual. Harvest windows are narrower (3–5 days vs 5–10 for photos) because the plant's biology moves faster and doesn't pause for light schedule. Check trichomes daily once cloudy trichomes appear — the window closes faster than photos.
The tool excludes the transition phase from auto timelines entirely and uses compressed seedling durations (7–14 days vs 14–21 for photos) to reflect the faster auto biology.
The stop-feeding timing: why 10 days
The tool's stop-feeding milestone is set 10 days before harvest window opens. This allows a 7-day plain-water flush plus a 3-day buffer for plants to pull stored nutrients from fan leaves (normal end-of-life leaf yellowing, not a deficiency). Different growers use 7–14 days depending on medium and nutrition program — coco and hydro can flush in 24–48 hours; soil takes longer due to organic material buffering. The 10-day default is a conservative middle ground. Use Feed Health Tracker to monitor runoff EC during flush and confirm salt levels are dropping.
Where the numbers come from
Phase duration defaults are derived from consensus cultivation guides and validated against three independently published cannabis horticulture references (Cervantes, Clarke, and Rosenthal). Flower variance multipliers (indica ×0.90–1.00, hybrid ×1.00–1.10, sativa ×1.00–1.25, auto ×0.90–1.20) represent the typical range observed in home-grow communities and align with published phenotype variance data. Harvest window widths (indica 5–8 days, hybrid 6–10, sativa 7–14, auto 3–7) are empirical estimates from experienced growers reporting optimal chop timing via trichome inspection across multiple grows. Stop-feeding timing (10 days) is the midpoint of the 7–14 day range recommended across major nutrient line documentation.
Common germination and grow timing questions
How long does a cannabis grow actually take from seed to harvest?
For a typical photoperiod hybrid grow from seed: germination (5 days) + seedling (17 days) + veg (35 days untrained) + transition (10 days) + flower (63 days for a 9-week strain) + harvest window (4 days to peak) = about 134 days, or just over 4 months. Add drying (7–14 days) and curing (2–6 weeks) before smoke-ready, and you're looking at 5–6 months total. The most common grower mistake is forgetting that "9-week flowering strain" means 9 weeks from flip, not 9 weeks from seed — the whole grow is much longer. Autoflowers compress this to 3–4 months from seed to harvest but require a full cure as well.
Seeds or clones — which gives a faster harvest?
Clones, by 3–4 weeks. Seeds need 5 days germination + 17 days seedling before they're ready for veg; clones skip both phases entirely and go straight into veg (assuming you have rooted clones ready). The tradeoff: clones require a mother plant or a reliable source, and they propagate any pathogens (pests, disease) from the mother. Seeds offer genetic variety and a clean start every grow. For perpetual growing, clones from a known mother are the standard approach. For single first grows, seeds are simpler to source.
My plant is past the breeder's stated flower time and still not done — what's happening?
Normal for many strains — breeder timelines are averages, and individual phenotypes routinely run 1–3 weeks longer. Most common causes beyond plain phenotype variance: room running cool (below 70°F slows flower development), VPD out of range (causes plant stress, slows maturation), light leak during dark period (disrupts hormonal signaling, can send plants back into semi-veg), and nutrient issues causing stress. Sativa-dominant strains are especially prone to running long. Check trichomes rather than the calendar — if trichomes are still clear-dominant at week 12, something is limiting, but if they're cloudy, the plant is right on schedule regardless of the calendar date.
Can I veg longer than the tool's recommended time?
Yes — veg duration is entirely your call. Longer veg = larger plant = higher potential yield, up to a point. The constraint is physical space: a plant flipped at 18 inches will be 36–48 inches by end of transition (plants typically double in height after flip). If your ceiling is 7 feet, you have a hard limit. SCROG is the training method that lets you maximize veg time productively — you fill the screen until it's 70–80% covered, then flip. The Pro mode's veg override field lets you enter your specific planned veg duration if you know it.
What does the "transition" phase mean and why is it separate from flower?
Transition is the 1–2 weeks immediately after flipping to 12/12 before visible flower sites appear. During this window, the plant is responding hormonally to the light schedule change — progressing from vegetative growth to reproductive mode. You see significant vertical stretch (plants can double in height) and the beginning of pre-flower pistil development, but no real bud structure yet. Feeding during transition mirrors early veg + beginning-of-flower nutrition (gradually ramping down nitrogen, beginning to introduce phosphorus). The tool separates it because it's often where height management issues get missed — growers are surprised by how much their plant stretches after flip.
How does a perpetual harvest setup work?
Perpetual growing staggers multiple batches so harvests arrive at regular intervals instead of all at once. Classic two-tent setup: one veg tent (18/6) always running, one flower tent (12/12) always flowering. Every 4–6 weeks, the most mature flowering plants are harvested, the oldest veg plants move to the flower tent, and fresh clones or seedlings fill the veg tent. The Pro mode's batch planner shows you exactly when each batch starts and harvests at whatever stagger interval you choose. If staggering feels logistically complex, start with 2 batches 4 weeks apart before adding more.
When does the calendar say to stop nutrients, and why that timing?
10 days before the harvest window opens. This allows roughly 7 days of plain-water flushing (which pulls accumulated salts from the growing medium) plus a few days of buffer. Soil takes longer to flush than coco or hydro because organic matter buffers pH and holds onto nutrients. Signs the flush is working: fan leaves start yellowing (normal — plant is consuming stored nutrients), runoff EC drops toward your water's starting EC. Monitor runoff EC with a meter rather than just counting days; in hot weather or with smaller pots, the flush completes faster. The Feed Health Tracker can help confirm the flush is effective.
Does the calendar account for drying and curing time?
Not explicitly — the calendar ends at peak harvest date. Plan 7–14 days of hanging dry (test doneness with stem snap: dry branches snap cleanly, still-wet branches bend) plus a minimum 2-week jar cure, ideally 4–6 weeks for best flavor. So from harvest day to smoke-ready is typically 3–8 weeks depending on your dry environment and how long you cure. Budget this into your event planning if you're working backwards from a specific date you want to enjoy the result.
Propagation gear and germination supplies
The germination phase has one of the highest gear-to-success ratios in the whole grow. A $15 humidity dome eliminates most seedling failures. $30 of rockwool or Rapid Rooters solves the "my clones won't root" problem. Investing early in the right propagation setup saves weeks of lost grow time.
Seed starter kits & humidity domes
Propagation trays with domes ($15–25), seedling heat mats ($20–35), 72-cell seedling plugs. Humidity domes maintain the 70–80% RH seedlings need without constant misting. Heat mats bring soil to optimal germination temperature (75–80°F). Essential for consistent germ rates.
Cloning supplies
Rockwool cubes or Rapid Rooters ($10–15), rooting hormone powder or gel ($8–15), cloning collars, clone nutrient solution. Rapid Rooters and rockwool work best with a small amount of rooting gel at the cut. Keep domed at 75–80°F and 80–90% RH during rooting.
Seedling & clone lights
T5 fluorescent or LED seedling boards ($30–80), full-spectrum small LED panels ($50–120). Seedlings and clones need low-intensity light (100–200 PPFD) to avoid stress. Full-spectrum CMH T5 produces strong seedlings. Keep 18/6 schedule from day 1 for photoperiods.
Germination media
Jiffy peat pellets ($10), Root Riot plugs ($10), rapid rooter trays ($12), starter cubes. Pre-soak Jiffies and Rapid Rooters in pH 6.0–6.5 water before use. Don't over-water — moist not wet is the mantra. Check for taproot emergence before moving to final medium.
Seedling & clone nutrients
Rooting hormone (Clonex gel, TakeRoot powder), Cal-Mag for coco seedlings, light veg nutrients (0.5–0.8 EC max for seedlings). Don't feed heavy during seedling — over-nutrient is the most common seedling killer. Start nutrients only after first true leaves appear.
Propagation meters
Probe thermometers for soil temp ($10–15), small digital hygrometers for dome humidity ($8–15), pH meter for germination water ($30–60). Soil temperature is more critical than air temperature for germination — soil should be 75–80°F, not just air. Check pH of water before soaking any media.