Short answer
Outdoor cannabis is ready when calyx trichomes are mostly cloudy with some amber, roughly 5–20%. At 35–50° latitude that is usually mid-September to late October in the Northern Hemisphere and March to April in the Southern. Cloudy versus amber is a matter of preference (house position). Grower practice, and the weather can overrule it.
Why
Plants ripen at their own pace. Trichome maturation differs by genotype and plant age, and heads on one bract mature unevenly [1].
Cannabinoids plateau, then fall. In hemp, totals peaked about 6–7 weeks after flowering began, then declined with senescence [2]. Leaving plants "for more amber" past the plateau costs quality.
Autumn weather is the outdoor grower's real deadline. Gray mould (botrytis) thrives in cool, wet weather and dense flowers [3], and bud rot is the main late-season outdoor loss [4].
The calendar follows the flowering date. Plants that set flower in mid-August and carry an 8–10 week cultivar, plus the 10–14 day transition, finish in mid to late October.
The numbers
| Cultivar type | Northern Hemisphere (35–50°) | Southern Hemisphere (35–50°) |
|---|---|---|
| Early outdoor lines, autoflowers | Late August–late September | Late February–late March |
| Typical drug-type photoperiods | Late September–late October | Late March–late April |
| Late, tropical-leaning lines | November or later | May or later |
| Trichome target | Mostly cloudy, ~5–20% amber, a few clear | Same |
What to do
- Note when pistils first showed; count the cultivar's weeks from then.
- From two weeks before the expected date, check calyx trichomes at the top, middle and bottom with a 60–100x loupe.
- Keep feeding; taper nitrogen in the final weeks rather than flushing.
- Watch the 10-day forecast. Harvest near-ripe plants before long rain or a hard freeze.
- After rain, shake colas dry and open the biggest ones to check for grey mould.
- Harvest the ripest tops first if lower buds lag.
Common mistakes
- Leaving plants through a week of rain for a few more amber heads.
- Reading sugar-leaf trichomes, which amber early.
- Pre-harvest flushing, a Myth that starves the plant at its most important stage.
- Choosing a 12-week cultivar where first frost comes in early October.
Related
- Full article: Trichome ripeness: clear, cloudy, amber, and what the evidence says
- Answers: How to check trichomes · When outdoor plants flower · Harvesting too early or late
- Articles: Botrytis bud rot · The flush debate
- Terms: outdoor growing
