The pick: flush when you feed salt based nutrients
Run plain water for the final 7 to 10 days if your plants get bottled salt based nutrients. Salt feeds stack in the medium over a grow, and a plain water window gives the root zone a reset before chop. If your plants sit in living soil or get slow release organic inputs, skip the flush. You gain nothing and you risk starving a plant that still needs to bulk up.
cannabis flush schedule for soil
That is the whole decision. What follows is how to run each path, and where convenience tips the scale.
Flush vs no flush: what changes
- Flush: plain pH adjusted water for 7 to 10 days, runoff EC drops, lower leaves yellow first.
- No flush: feed chart runs to the end, no starvation yellowing, more mixing work each week.
- Flush risk: yield loss if you start too early or stretch past 14 days.
- No flush risk: more salt residue in the medium, so curing needs closer attention.
Prerequisites for either method
- Know your feed type: bottled salts, dry organic, or living soil.
- A way to read runoff EC or ppm.
- A pH meter and pH adjuster.
- A planned harvest date on the calendar.
How to flush, step by step
- Count back 7 to 10 days from your planned harvest date and mark the start.
- Stop all nutrient mixes. Fill the reservoir with plain water.
- Set pH to your normal range: 6.0 to 6.5 in soil, 5.8 to 6.2 in coco.
- Water to runoff and measure the runoff EC on the first pass.
- Repeat plain water feeds on your normal watering schedule.
- Test runoff EC every second watering. Stop flushing once runoff reads within 0.2 EC of your input water.
- Harvest on schedule. Do not extend the flush past 14 days.
How to run no flush, step by step
- Keep the feed chart running to harvest.
- Cut nitrogen in the final two weeks and hold phosphorus and potassium steady.
- Water to runoff at each feed to limit salt stacking.
- Stop feeding 2 to 3 days before harvest and water only.
- Dry at 60 F and 60% humidity, then cure for 14 days.
Where convenience decides
Convenience has become the deciding factor for most home growers, and it cuts both ways. Flushing is the lower effort path: one reservoir change, plain water, no measuring. No flush keeps the routine intact and avoids a second nutrient recipe, which matters if you run several plants on different schedules. Pick the path that matches the work you will actually do on day 8, not the one that sounds cleaner in theory.
cannabis flushing nutrients guide
Options if you want a middle path
- Short flush: 3 to 5 days of plain water, then harvest.
- Half strength feed for the final 10 days, no plain water window.
- Split approach: flush in coco, keep feeding in soil.
- Water only for the last 3 days on any method.
Bottom line
Flush salt fed plants. Leave organic and living soil plants on feed. Test runoff if you want proof the medium dropped, and keep the final two weeks on the calendar so harvest does not drift.