Crop Steering Chart: Vegetative vs Generative
One page with the levers growers use to push cannabis toward leaf and stem growth (vegetative) or toward flower development (generative). Use it as a starting point, then adjust to what your own plants and root zone show you.
Download the chart as a PDF (one page, prints on A4 or Letter).
Irrigation
| Lever | Vegetative | Generative |
|---|---|---|
| First irrigation after lights-on | 0 to 1 h | 1 to 3 h (up to 4 h) |
| Last irrigation before lights-off | 0 to 2 h | 2 to 4 h |
| Shot size (% of substrate volume) | 1 to 3% | 3 to 6% |
| Irrigation frequency | Frequent, small shots | Fewer, larger shots |
| Dry-back between daytime shots | 1 to 3 VWC points | 3 to 8 VWC points |
| Overnight dry-back | 10 to 15% of peak VWC | 20 to 30% of peak VWC |
| Runoff | Regular runoff most days | Little or none; flush when EC climbs too high |
| Root-zone water content | Held near field capacity | Held below field capacity |
Root zone
| Lever | Vegetative | Generative |
|---|---|---|
| Substrate EC (bulk or pore-water) | 2 to 5 mS/cm | 4 to 10 mS/cm |
| Root-zone temperature | 18 to 24 °C (64 to 75 °F) for both | |
Climate
| Lever | Vegetative | Generative |
|---|---|---|
| Day air temperature | 25 to 29 °C (77 to 84 °F) | 21 to 26 °C (70 to 78 °F) |
| Day/night temperature difference | Small (0 to 3 °C) | Larger (3 to 6 °C) |
| Relative humidity | 65 to 80% | 45 to 65% |
| VPD | 0.8 to 1.1 kPa | 1.1 to 1.5 kPa |
| Light intensity | Moderate | Higher, if irrigation and CO2 can keep up |
When each direction is used
| Stage | Common direction | Why |
|---|---|---|
| Propagation and early veg | Vegetative | Build roots and a uniform canopy without stress |
| Late veg | Vegetative, a few generative days before flip | Harden plants before the switch |
| Flower weeks 1 to 3 (stretch) | Generative | Limit stretch and push flower sites |
| Flower weeks 4 to 6 (bulk) | Back toward vegetative | Biomass demand is highest; do not starve the plant |
| Final 2 to 3 weeks (finish) | Mixed; no settled consensus | Larger dry-backs are common; high EC late is disputed |
Read this before using any number above.
These are ranges published across commercial grower guides, not targets proven for your cultivar. Dry-back is written as a percentage of peak VWC; if your guide uses VWC points or field capacity, convert first. Change one lever at a time and watch how the plants respond for several days before changing the next.
How to read the chart
Vegetative steering tells the plant conditions are easy: plenty of water, low salt in the root zone, soft climate. The plant responds with leaves, stem and roots. Generative steering adds controlled stress: the root zone dries further, EC builds, the air is drier. The plant shifts toward flowers and a more compact structure.
The irrigation rows are the strongest levers. The timing of the first and last shot of the day sets how far the substrate dries overnight, which is why most growers steer with timing before they touch EC or climate.
Too far in either direction costs yield. Excessive generative stress gives weak plants and small flowers. Research on cannabis has not shown that severe drought raises total cannabinoid yield; it can raise concentration while cutting biomass. See steering by growth stage for what the evidence supports.