Do I flush before harvest, or just keep the feed light to the end?

GROWER ANSWER

In soil, don't flush. Keep feeding her right through to the end, just lighter. A long run of plain water before harvest won't make her finish sooner, and it won't unlock food she can't take up. Mostly she just goes hungry while she's still filling out.

Ease the feed down. Don't take it away.

This page is written for soil. Coco and hydro get their own note below.

What plain water does this late, and what it doesn't

Here's what plain water can and can't reach.

• It doesn't speed up the finish. Her genetics and your light schedule set that clock. Taking her food away doesn't move it.

• It doesn't unlock food she can't take up. When food is in the soil and she can't use it, the cause is usually the pH or the roots, and plain water fixes neither. It can rinse out loose salts, which is what a small reset is for. Over two weeks it mostly lowers what she has left to eat.

• It doesn't cause the fade. In the last 2 to 3 weeks she pulls stored food out of her older leaves and moves it up into the flowers, flush or no flush. Taking her food away just makes the fade show sooner.

• It changes the pot, not what's already in her. Plain water changes what her roots find next. What's already inside her, she keeps or moves on her own.

So the yellow after a flush isn't proof it worked. Often it's the same fade, arriving early on a hungry plant.

Read it in this order

1. Keep the rhythm, lighten the strength. Water and feed on your usual schedule. If your feed chart steps the strength down late in flower, take that step and hold it to the end. Light, not none.

2. Match the finish to your soil. A rich, well-amended mix can carry her a long way, and some finish on water alone. A lighter bagged mix usually wants feeding a little longer. In a living soil there's nothing to flush: the soil is doing the feeding, so water as usual.

3. Read the plant, not the calendar. A fade that starts on the oldest leaves and moves slowly up the plant is her finishing. Change nothing.

4. Only test for a buildup if she shows one. Burnt tips spreading onto new growth, or leaves clawing down, earn a runoff reading. Take it the same way each time: the same pot, at the same point in the dry back, with a calibrated meter, written down next to what you fed. In soil that gap is a loose signal, because what drains out picks up whatever is in the soil on the way. One reading isn't a reason to flush. A gap that keeps climbing over a few waterings, with the plant showing it too, is worth acting on.

5. If a buildup is confirmed, reset small. Plain pH'd water or a very light feed, half strength or less, for a watering or two. Then a full dry back, and back to the light feed. That's a reset, not a two-week flush.

Then call the harvest by the flowers.

Does a flush change the taste?

Growers argue this one hard, both ways. We have no tested number on it that we'd stand behind, so this page makes no taste claim either way. What it does stand on: she finishes whether you flush or not, and cutting her food early costs her while she's still filling out.

Coco and hydro

These hold almost no food of their own, so what's in the water is all she gets. A planned, gentle ease-down toward the end is common there, and fine. What isn't fine in any medium is the sudden switch: full feed one day, plain water the next, because a date came up.

What not to do

Don't start a plain-water run off the calendar. Go by the plant, not a date.

Don't read the fade as proof the flush worked. She was going to fade anyway.

When it's something else

• Fan leaves yellowing and you want to pull them or feed more: see She's fading in late flower. Do I flush, feed or pull the leaves?

• A high runoff number earlier in the grow: see My runoff number is high. Should I flush?

• Deciding when to cut: see our Harvest Decision Guide

• Not sure she's getting enough food: see How can I tell when my plant wants more food?

On our shelf in Worcester: EC and pH pens and combo meters for reading your feed and runoff are in pH, water & meters. Call (508) 459-9609 or get directions.

Keep going

Taking a runoff reading you can trust: see our pH and EC meters shelf guide.

Watch the episode: Yellow Leaves in Late Flower? It's Not Dying, It's Finishing on MyRemy Live.

Watch the episode: Fan Leaves Yellowing Before Harvest? Don't Panic-Feed Her on MyRemy Live.

The finish is built long before the last weeks. The whole system for a steady grow is written down in the free Stability Playbook. Get the free Stability Playbook

More answers: all grow guides. Every shelf guide and maker feed chart: Grower Resources.