Canna Flush - Clean Substrates Before Harvest or After Overfeeding
Best for: Growers who need to clear excess nutrients from their substrate before harvest, or after accidentally overfeeding.
Our thoughts
Every grower overfeeds at some point, and running plain water through the substrate on its own doesn't always shift built-up salts properly. Canna Flush does the job without nuking the beneficial bacteria and fungi in your root zone the way reverse osmosis or demineralised water flushing can.
Canna Flush is a concentrate designed to strip excess nutrients out of both substrate and plant tissue. Left unaddressed, that build-up can cause over-fertilisation symptoms or lock out other nutrients, leading to deficiencies further down the line. It's most commonly used in the week or two before harvest to clean the plant out for a purer-tasting finish, but it works just as well as a fix if you've fed too heavily mid-grow.
It's suitable for any substrate, including inert media like clay pebbles, and CANNA states it cleans effectively without harming the useful microbial life in the root zone, unlike a straight RO or demineralised water flush.
How it compares
Flushing agents mostly differ in dilution rate and how gentle they are on substrate biology.
- Plain reverse osmosis or demineralised water works but can strip beneficial bacteria and fungi along with the excess salts
- Grotek's Final Flush targets a similar pre-harvest clean-out with its own dilution schedule
- Advanced Nutrients' Flawless Finish is aimed at the same late-flower clean-up stage, using a different active formulation
Canna Flush does a straightforward job at a low cost per use, without asking you to switch to RO water or buy a more expensive proprietary system.
Usage guidance
Dilution and timing depend on whether you're flushing soil, coco, or a fully hydroponic system.
Soil or soilless mixes
Dilute 20ml per 10 litres of water (1:500) and water until you see drain, then water once more with plain tap water before returning to your normal feeding schedule.
Hydroponics (open/run-to-waste systems)
Use 40ml per 10 litres (1:250) as the last feed of the day until you get 10-20% drain, then water with plain tap water and resume normal feeding the following day.
Before harvest
Start one to two weeks before harvest and apply at the above rates once a week, continuing through to harvest on your normal schedule otherwise.
Reusing inert substrates
Add diluted Canna Flush (40ml per 10 litres) to clay pebbles or similar, soak for 24 hours, then rinse with the same volume of tap water, repeating if needed.
Technical specifications
- Function: Substrate and plant flushing agent (removes excess nutrient salts)
- Dilution, soil/soilless: 20ml per 10L water (1:500)
- Dilution, hydroponics: 40ml per 10L water (1:250)
- Suitable substrates: All substrates, including inert media
- Pack sizes: 250ml, 1L, 5L
- Bottle material: Polyethylene (PVC and cadmium free), recyclable
- Brand: CANNA
Who this is for
- Growers preparing for harvest who want a cleaner-tasting finish
- Anyone who has overfed and needs to correct a nutrient build-up
- Growers reusing inert media like clay pebbles between cycles
- Hydro and coco growers wanting to avoid RO water for a simple flush
Best suited to being kept on hand for both routine pre-harvest flushing and as a fix when feeding has gone a bit too heavy.
Our take
It's a cheap bit of insurance either way - a routine step before harvest, or a quick fix if you've overdone the feed. Either way it earns its place on the shelf.
Does exactly what it should, day in, day out, and it's priced low enough to just keep a bottle around for whichever job comes up first.
