Cannabis Growing Week by Week: Seed to Harvest Timeline

One of the first questions every new grower asks is simply “how long does this take?” The honest answer is that a cannabis plant runs on its own biological clock, and the more you understand that rhythm, the calmer and more successful your first grow becomes. This guide walks through the plant’s life stage by stage so you know what to expect each week from seed to harvest.

A quick note on the law first. Following the 2018 Prince judgment by the Constitutional Court, private cultivation and use of cannabis by adults (18+) for personal consumption in a private place was decriminalised in South Africa. Growing a few plants at home for yourself is treated very differently from dealing — selling or supplying cannabis remains illegal. For the full picture, read our overview of whether dagga is legal in South Africa before you begin.

Weeks 1–2: Germination and the seedling stage

Everything starts with a viable seed. Germination is the moment the taproot breaks the shell, and it usually takes two to seven days in warm, moist conditions. Whether you use the paper-towel method or plant directly into a light starter mix, the goals are the same: gentle warmth (around 22–25 °C), moisture without waterlogging, and darkness until the root emerges. For a deeper look at this phase, see our companion guide on growing cannabis from seed.

Once the seedling pushes its first round “seed leaves” (cotyledons) above the surface, followed by the first serrated true leaves, it enters the seedling stage. This lasts roughly one to two weeks. Seedlings are delicate: they want humidity, gentle light and very little feeding. Overwatering is the single most common way to lose a plant at this age, so let the top of the medium dry slightly between waterings.

Weeks 3–6: The vegetative stage

Now the plant shifts into its growth engine. During the vegetative stage it builds roots, stems and fan leaves as fast as its environment allows, but produces no flowers yet. This is where you shape the plant — topping, low-stress training and tidying up lower growth all happen here.

Light is the master switch. Photoperiod plants stay in vegetative growth as long as they receive long days, so indoor growers run an 18 hours light / 6 hours dark (18/6) cycle to keep them vegetating. Outdoors in South Africa, the long summer days do this naturally. How long you veg for is up to you: a couple of weeks gives a small plant, four to eight weeks gives a large one. Bigger plants need bigger pots and more space, so match your veg length to your grow area. The choice between a tent and the open sky is covered in indoor vs outdoor growing.

Weeks 7–8: The flowering switch and stretch

Flowering begins when the plant senses shorter days. Indoors you trigger it deliberately by switching to a 12 hours light / 12 hours dark (12/12) cycle. Outdoors it happens on its own as autumn approaches and daylight shortens. Within a week or two you will see the first signs of sex: female plants show fine white hairs (pistils) at the nodes, while males form small pollen sacs. Most growers remove males early, because only unpollinated females produce the dense, resinous flowers you are after.

The start of flowering also brings the “stretch”, a burst of vertical growth where the plant can double in height over two to three weeks. Plan your space for this — a plant that fits your tent in veg can crowd the light after the stretch.

Weeks 9–14: Bud development

After the stretch settles, the plant pours its energy into building flowers. Small clusters swell into fuller buds, pistils multiply, and a frosting of resin glands (trichomes) begins to coat the flowers and surrounding leaves. Nutrient needs change here too — plants generally want less nitrogen and more phosphorus and potassium during flowering, as explained in our guide to cannabis nutrients, soil and feeding.

Aromas intensify in these weeks, which is worth planning for if discretion matters to you. This is also the stage where problems become costly, so keep airflow steady and humidity moderate to avoid bud rot. Our guide to common growing problems covers what to watch for.

Weeks 14–16: Ripening and harvest

In the final couple of weeks the pistils darken and curl inward, and the trichomes shift from clear to milky-white and eventually amber. This colour change is your best harvest signal. Most photoperiod plants finish roughly 8 to 11 weeks after the flip to 12/12, though the exact timing depends on the genetics. When the flowers look ripe, it is time to cut — and then the equally important work of drying and curing begins, which we cover in harvesting, drying and curing.

The autoflower shortcut

Autoflowering plants ignore the light-cycle rules entirely. They flower automatically after a few weeks of age regardless of day length, so many growers run them under 18/6 or even 20/4 from start to finish. The trade-off is speed for size: a typical autoflower goes from seed to harvest in around 8 to 12 weeks total, producing a compact plant. Because they cannot be re-vegged if something goes wrong, get their early care right the first time.

Every grow is a little different, and weather, genetics and your own set-up all shift the calendar. Treat these weeks as a map rather than a stopwatch, and let the plant’s own signals guide you. For the full learning path, start at our grow hub or the broader home cultivation guide for South Africa.