How long does it take to grow weed indoors? With photoperiod varieties it usually takes 14–20 weeks from seed to harvest, or roughly 3–4.5 months: about 1 week of germination, 2–3 weeks as a seedling, 3–6 weeks of vegetative growth and 8–10 weeks of flowering. Autoflowers complete the cycle in 8–12 weeks; in both cases, add 1–2 weeks of drying and at least 2–4 weeks of curing after cutting.
In brief
- Photoperiod plants: 14–20 weeks from seed to harvest; the vegetative stage is the one you can stretch or shorten.
- Autoflowers: 8–12 weeks in total, on the same light schedule from start to finish.
- Flowering lasts 8–10 weeks for most varieties and cannot be shortened without losing quality.
- With a single tent you can run 2.5–3.5 photoperiod cycles a year, or 4–5 autoflower cycles.
Timeline stage by stage
| Stage | Typical length | Light schedule | When to move on |
|---|---|---|---|
| Germination | 1–7 days | Dark until the taproot appears | The cotyledons open |
| Seedling | 2–3 weeks | 18/6 | 3–4 pairs of true leaves |
| Vegetative stage | 3–6 weeks | 18/6 | Plant at about half its final height |
| Flowering | 8–10 weeks | 12/12 | Milky trichomes, most pistils darkened |
| Drying | 7–14 days | Dark | Small stems snap |
| Curing | At least 2–4 weeks | Dark | Humidity steady at 58–62% in the jar |
The flowering time on the variety's data sheet is a guide only: some varieties finish in 7 weeks, others take more than 11. The trichomes tell you when the time is right, not the calendar; what happens week by week is explained in the guide to flowering week by week.
Autoflowers and photoperiod plants
- Photoperiod plants flower when the nights get longer: indoors you trigger flowering by switching to 12 hours of light and 12 of darkness (12/12), outdoors they start by themselves once daylight drops below about 14–15 hours. Indoors you decide when, and with it how long the vegetative stage lasts.
- Autoflowers start flowering on their own after 3–5 weeks, on 18/6 or 20/4 from start to finish. The cycle is shorter, but a mistake in the first weeks cannot be made up by extending growth.
- Autoflowers usually stay smaller and suit low tents; care and pot choice are covered in the guide to growing autoflowers.
Indoors and outdoors in Switzerland
Indoors the timer sets the calendar and you can start in any month. Outdoors the sun decides: seedlings are started indoors between late March and April and go outside after the Ice Saints, in mid-May. Photoperiod plants keep growing while the days are long, start flowering between late July and mid-August and are harvested between late September and October, depending on variety and weather. That is 5–7 months from sowing and a single harvest a year; with autoflowers, south of the Alps, two cycles a year are possible, and a third only with early sowing in April, a favourable spot and a favourable year; the dates are in the outdoor grow calendar for Ticino.
How many indoor cycles a year
| Set-up | Time in the tent per cycle | Cycles per year |
|---|---|---|
| Photoperiod from seed, one tent | 14–20 weeks | 2.5–3.5 |
| Autoflowers, one tent | 8–12 weeks | 4–5 |
| Two spaces: veg and flowering | 8–10 weeks in the flowering tent | 4.5–5.5 |
The figures allow 1–2 weeks between cycles to clean and prepare the tent; if you dry in the same tent, go with the lower figure. The two-space set-up needs a second, small grow tent with a low-power LED, where the next plants grow while the previous ones flower.
Shortening or extending the vegetative stage
In the first 2–3 weeks of flowering the plant keeps stretching, often by 50–100%. That is why you switch to 12/12 once it has reached about half the height available under the lamp. More detail in the guide to the vegetative stage.
- To shorten it: more small plants per m², start from rooted cuttings, veg for 1–3 weeks.
- To extend it: few plants, topping, LST or a net (SCROG), veg for 5–8 weeks to fill the space.
- Every extra week of veg adds a week to the whole cycle; flowering stays the same length.
Planning with a grow diary
An example with a photoperiod plant: germination on 1 March, seedling from 8 March, veg from 22 March for 4 weeks, switch to 12/12 on 19 April, 9 weeks of flowering and harvest around 21 June. Drying until early July and curing until at least 22 July.
- Record the key dates: germination, repotting, switch to 12/12, first pistils, harvest.
- Every week: height, water pH and EC, minimum and maximum temperature and humidity, and a photo from the same spot.
- At the end of the cycle, compare the actual weeks with the variety data sheet: it is the most reliable basis for planning the next one.
Frequently asked questions
How long is it from seed to harvest?
Indoors, 14–20 weeks for photoperiod plants and 8–12 for autoflowers. Outdoors in Switzerland, 5–7 months between late March and October.
How many harvests a year are possible indoors?
With one tent, 2.5–3.5 photoperiod cycles or 4–5 autoflower cycles. With one space for veg and another for flowering, you can reach about 5.
How much time is needed after harvest?
Another 3–6 weeks: 7–14 days of drying in the dark at 18–21 °C, then at least 2–4 weeks of curing in jars at 58–62% humidity. Allow for this time when you plan the next cycle, if you dry in the same tent.
Are autoflowers faster?
Yes: 8–12 weeks from seed to harvest instead of 14–20. In return the plants are smaller and you cannot adjust how long they grow.
Tent, light and extraction already matched for a first cycle are available in the complete grow tent kits.
Updated on 13 October 2026.