# Your first grow: a plan from seed to jar

> For a first indoor grow, use one to four plants of a reputable feminised autoflower or photoperiod line in a tent, a good LED, quality soil or coco, a pH and EC meter, and a journal. Keep the targets simple: steady temperature and humidity, light to about 400-600 µmol/m²/s in veg and 600-900 in flower, water by weight, and harvest by trichomes.

- Canonical: https://genetixbay.com/knowledge/basics/first-grow-guide.html
- Category: Basics · Level: Beginner
- Evidence: Supported · Status: Draft: awaiting expert review
- Stage: Any stage · Systems: Soil, Coco
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Questions and answers

**What do I need for my first cannabis grow?** A first indoor cannabis grow needs a grow tent, one good LED light, a fan and [carbon filter](https://genetixbay.com/knowledge/glossary/carbon-filter.md), 11-19 L (3-5 gal) pots of quality soil or coco, a [pH pen](https://genetixbay.com/knowledge/glossary/ph-meter.md), an [EC meter](https://genetixbay.com/knowledge/glossary/ec-meter.md) and a journal, plus one to four plants of a well-documented feminised line. Check that home growing is legal where you live first. Most first grows fail from overwatering and overfeeding, not from too little gear.

**Should a beginner grow autoflowers or photoperiods?** Either works for a beginner. Feminised autoflowers finish fast, in about 9-14 weeks, and need no light-schedule change, but they have no time to recover from mistakes. Feminised photoperiods give control over size and allow cloning and training practice, but you must flip them to [12/12](https://genetixbay.com/knowledge/glossary/12-12.md) and keep the dark period truly dark. Whichever you choose, pick a line with real grow journals.

**How much light does cannabis need?** Cannabis grows well indoors at about 150-300 µmol/m²/s PPFD for seedlings, 300-600 in veg and 600-900 in flower, rising to about 1,200 with added CO2 and experience. That works out to a DLI of roughly 10-20, 20-40 and 26-40 mol/m²/day. Research shows yield kept rising roughly linearly with light up to about 1,800 µmol/m²/s, but beginners should not chase that.

**How often should I water my plants?** Water cannabis when the pot feels light, not on a fixed schedule. Lift the pot to learn its wet and dry weight, then water to about [10-20% runoff](https://genetixbay.com/knowledge/glossary/watering-to-runoff.md) in coco and less in soil. Seedlings need only a small ring of water around the stem. Overwatering is the most common first-grow failure, and drowned roots often look like hunger, which tempts growers into overfeeding too.

**Soil or coco for a first grow?** Both soil and coco work for a first cannabis grow in 11-19 L (3-5 gal) pots. Quality organic soil is forgiving, may need plain water only for weeks, and runs at pH 6.2-6.8. Coco needs feeding from early on, at pH 5.8-6.2 and a feed EC rising from about 0.4-0.8 mS/cm for seedlings to 1.6-2.2 mS/cm in flower, watered to 10-20% runoff.

**What temperature and humidity should my tent be?** A cannabis grow tent should run about 24-27 °C (75-81 °F) and 65-75% RH for seedlings, 22-28 °C (72-82 °F) and 55-70% RH in veg, and 20-26 °C (68-79 °F) with 45-55% RH in flower, dropping to 40-50% late in flower to cut bud rot risk. Matching VPD targets are about 0.4-0.8, 0.8-1.2 and 1.0-1.5 kPa.

**Short answer.** Start small and boring: a tent, one good LED, a fan and carbon filter, 11-19 L (3-5 gal) pots of quality soil or coco, a pH pen and an EC meter. Grow one to four plants of a well-documented feminised line. Write everything down. Most first grows fail from overwatering, too much nutrient and too much fiddling, not from too little gear.

**Legal first.** Home growing is legal only in some places, with [plant limits](https://genetixbay.com/knowledge/glossary/plant-count-limit.md) and rules about visibility and security. Check your local rules and the GenetixBay regional page before buying seed.

## What's happening

A plant needs light, water, air at the roots, nutrients and a stable climate. Each has a "good enough" window. A first grow is about staying inside the windows and learning what your plant looks like when it is happy.

## Choose your genetics

| Option | Good for | Watch out |
|---|---|---|
| Feminised autoflower | Speed (9-14 weeks), small spaces, no light-schedule change | No time to recover from mistakes; don't top late |
| Feminised photoperiod | Control over size, cloning, learning training | You must flip to 12/12 and keep the dark period dark |
| Regular seed | Breeding later | Half will be males to remove |

Pick a line with a GenetixBay record at L2 or higher and real grow journals. See [seed types](https://genetixbay.com/knowledge/basics/seed-types-regular-feminised-auto-clone.md).

## Numbers that matter

| Parameter | Seedling | Veg | Flower | Notes |
|---|---|---|---|---|
| PPFD (µmol/m²/s) | 150-300 | 300-600 | 600-900 (up to ~1,200 with CO₂ and experience) | Yield rose roughly linearly with light up to ~1,800 in one study [1]; beginners should not chase that |
| DLI (mol/m²/day) | 10-20 | 20-40 | 26-40 | DLI = PPFD x hours x 0.0036 |
| Photoperiod | 18/6 | 18/6 | 12/12 (photos); 18/6-20/4 (autos) | Dark must be dark [4] |
| Air temperature | 24-27 °C (75-81 °F) | 22-28 °C (72-82 °F) | 20-26 °C (68-79 °F) | Net [photosynthesis](https://genetixbay.com/knowledge/glossary/photosynthesis.md) peaked ~25-30 °C in [2] |
| RH | 65-75% | 55-70% | 45-55%, 40-50% late | Lower late to reduce bud rot risk |
| VPD (kPa) | 0.4-0.8 | 0.8-1.2 | 1.0-1.5 | Leaf-temperature based |
| pH (soil / coco) | 6.2-6.8 / 5.8-6.2 | same | same | Measure what goes in and what runs off |
| Feed EC (mS/cm, coco) | 0.4-0.8 | 1.0-1.8 | 1.6-2.2 | Organic soil may need water only for weeks [3] |

These are *Grower practice* ranges anchored to the cited studies; your cultivar may differ.

**Pot size is a trade-off.** Bigger pots give bigger yields within reason and forgive missed waterings; smaller pots can still produce big plants if you water and feed often (the founder has grown 4 oz+ from a 16 oz cup). For a first grow, 11–19 L (3–5 gal) is the forgiving choice.

## Step by step

1. **Set up and test the room for 48 h before seeds.** Log temperature and RH day and night. Fix the climate first.
2. **Germinate** in moist paper towel or directly in a small pot at 22-26 °C (72-79 °F). Plant root-down 0.5-1 cm (¼-½ in) deep.
3. **Seedling (1-3 weeks).** Light gentle, water a small ring around the stem. Do not feed most [bagged soils](https://genetixbay.com/knowledge/glossary/potting-mix.md) yet.
4. **Veg.** Pot up when roots fill the container. Water when the pot feels light, to 10-20% runoff in coco, less in soil. Begin training (low-stress tying down) on photoperiods.
5. **Flip (photoperiods only).** Change to 12/12 when plants are about half the final height you can fit. Expect them to stretch. The flip isn't day 1 of flower: pistil clusters usually show 10–14 days later, so log both dates (see [the flip-to-flower transition](https://genetixbay.com/knowledge/environment/flip-to-flower-transition.md)).
6. **Flower.** Keep the dark period uninterrupted. Lower RH. Check for pests weekly with a loupe.
7. **Ripening and harvest.** Keep feeding at the strength the stage calls for right up to harvest; if you mix single salts, taper only nitrogen over the last few weeks. Don't flush before harvest: it's a *Myth* that starves the plant while it packs on its final weight, trichomes and resin, so it costs you yield and resin (see [the flush debate](https://genetixbay.com/knowledge/harvest-cure/flush-debate.md)). Look at [trichome heads](https://genetixbay.com/knowledge/glossary/trichome-heads.md) with a 60x loupe: harvest when most are cloudy and some amber, not by the stigma colour.
8. **Dry** whole branches at ~18-21 °C (64-70 °F) and ~55-62% RH for 7-14 days, until small stems snap. Trim wet before hanging or dry afterwards: it's grower preference. [Dry trimming](https://genetixbay.com/knowledge/glossary/dry-trim.md) (brushing the sugar leaf off a dry bud) is easier on the hands; [wet trimming](https://genetixbay.com/knowledge/glossary/wet-trim.md) suits a humid room. See [drying](https://genetixbay.com/knowledge/harvest-cure/drying.md).
9. **Cure** in airtight jars, opening briefly daily for the first week, then less often, letting the buds' moisture fall slowly. Judge the bud, not the air: a hygrometer reading only counts once the sealed jar has sat 12–24 h (aim for 55–65 %, aw 0.55–0.65). Skip [humidity packs](https://genetixbay.com/knowledge/glossary/humidity-pack.md); they're a marketing gimmick.

## Common mistakes

- Watering on a schedule instead of by pot weight. Drowned roots look like hunger.
- Feeding full strength from week one.
- Flushing with plain water for the last 1–2 weeks "for taste". It costs yield and resin; taste comes from a healthy plant, slow drying and a proper cure.
- Lights too close, especially strong LEDs: bleached tops, upward-cupped leaves.
- Changing three things at once when something looks wrong. Change one, log it, wait.
- Skipping the journal. A dated, photographed journal is the only way to learn from a grow, and on GenetixBay it is what links your harvest back to the seed pack.

## Evidence

- Light-yield relationship indoors: *Supported* (cannabis-specific trials) [1][2].
- Fertiliser rate in coir-based veg: *Supported* [3].
- Climate, VPD and dry/cure ranges: *Grower practice*.
- Autoflower timing: *Supported* genetics [5], timing is grower data.

## Sources

1. Rodriguez-Morrison V, Llewellyn D, Zheng Y. 2021. Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12:646020. https://doi.org/10.3389/fpls.2021.646020
2. Chandra S, Lata H, Khan IA, ElSohly MA. 2008. Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions. Physiology and Molecular Biology of Plants 14:299-306. https://doi.org/10.1007/s12298-008-0027-x
3. Caplan D, Dixon M, Zheng Y. 2017. Optimal rate of organic fertilizer during the vegetative-stage for cannabis grown in two coir-based substrates. HortScience 52(9):1307-1312. https://doi.org/10.21273/HORTSCI12401-17
4. Zhang M, Anderson SL, Brym ZT, Pearson BJ. 2021. Photoperiodic flowering response of essential oil, grain, and fiber hemp (Cannabis sativa L.) cultivars. Frontiers in Plant Science 12:694153. https://doi.org/10.3389/fpls.2021.694153
5. Toth JA, Stack GM, Carlson CH, Smart LB. 2022. Identification and mapping of major-effect flowering time loci Autoflower1 and Early1 in Cannabis sativa L. Frontiers in Plant Science 13:991680. https://doi.org/10.3389/fpls.2022.991680