Short answer. Pollinate when the female's stigmas are fresh and white, typically weeks 2-4 of flower. Brush or bag pollen onto labelled branches, keep the room still for a few hours, then wait about 5-7 weeks until the seeds are dark, hard and the bracts split. Contain pollen ruthlessly and write down every pollination.
Legal first. Producing seed may require a licence or be prohibited where you live, even where growing is legal. Check local rules before starting.
House position: males are a necessity. Real breeding needs real males, selected as carefully as the females. Males are encouraged and rewarded on GenetixBay, and a well-documented male line is a prized contribution. Selfing is mostly frowned upon: it was historically an emergency measure to save a line, not a shortcut. GenetixBay holds the best breeding standards: snobby, and proud of it.
What's happening
Cannabis is wind pollinated. A single male can shed enormous amounts of light, dry pollen that travels long distances outdoors (Established) [1]. Each female flower holds one ovule, so one pollen grain landing on a receptive stigma can make one seed. Pollen viability drops fast at room conditions [2], so fresh pollen or properly stored pollen matters.
Numbers that matter
| Parameter | Typical value | Notes |
|---|---|---|
| Female receptive window | ~weeks 2-5 of flower | White, upright stigmas; best early-mid flower (Grower practice) |
| Male pollen shed | ~2-4 weeks after flip, cultivar dependent | Sacs open from the bottom up |
| Pollen viability at room temp | Hours to a few days | [2] |
| Pollen viability at 4 °C | Mostly lost within 1 week (stage dependent) | Mid-stage pollen kept ~22% germination at 21 days [2] |
| Seed maturation | ~5-7 weeks from pollination | Earlier harvest lowers germination (Grower practice) |
| Seeds per pollinated branch | dozens to hundreds | Depends on branch size and coverage |
| Seed storage | Cool, dry, dark; ~5 °C maintained germination for years [5] | See seed testing |
Step by step
1. Plan the cross
- Choose the female (seed parent) and male (pollen parent) and record both GB-IND or GB-CUT IDs. Convention: write female x male.
- Decide whole plant (more seed, more pollen risk) or branch pollination (keeps the rest sinsemilla for evaluation).
2. Isolate
- Best: a separate room or tent for the male, with its own air. Collect pollen there.
- Keep fans off or low during pollination. Change clothes and wash hands and arms after handling males.
- Outdoors, other growers' males (and hemp fields) can pollinate your plants. You cannot guarantee parentage outdoors without bagging.
3. Collect pollen
- Cut a male branch with opening sacs, place it on clean, dry paper in still air for 12-24 h, then tap and sieve. See pollen collection and storage.
4. Pollinate
- Brush method: a clean, dry watercolour brush, lightly loaded, dabbed onto stigmas of a tagged branch.
- Bag method: slip a paper or fine-mesh pollination bag with a pinch of pollen over the branch, tie it, shake gently, remove after 24-48 h.
- Mist the plant lightly afterwards to knock down stray pollen in the air (Grower practice).
- Tag the branch: cross, date, pollen batch.
- Repeat after 3-5 days for better coverage if needed.
5. Mature
- Keep flowering conditions. Stigmas on fertilised flowers shrivel within a few days.
- Watch for bud rot: swelling seed pods hold moisture.
- Seeds are ready when the bracts split and seeds are dark, mottled (or uniformly dark) and hard when squeezed. Pale green or white seeds are immature.
6. Harvest and clean
- Dry the seeded branches for 1-2 weeks, then rub buds over a screen. Discard tiny, pale or cracked seeds.
- Dry seeds further at room temperature in a paper envelope for about a week, then store cool and dry.
7. Record and test
- Record: parents, pollination dates, harvest date, seed count, viability test. On GenetixBay this is a GB-BAT batch record with a
pollinationevent. - Run a germination test before you share or sell any seed.
Common mistakes
- Accidental pollination of the whole room from a single forgotten male or hermaphrodite.
- Saving seed from an accidental herm pollination. It carries the herm tendency; discard it.
- Pollinating too late in flower: low seed set and immature seed at harvest.
- No tags. Six weeks later you won't remember which branch got which pollen.
- Selling or gifting seed without a germination test.
Evidence
- Wind pollination and pollen dispersal: Established [1].
- Pollen viability decline at room and fridge temperature: Established (cannabis-specific assay) [2].
- Receptive window, maturation time, bag and brush methods: Grower practice.
- Reversed-female pollen for feminised seed: Established [3][4].
- Seed storage at ~5 °C: Supported [5].
