Canna - PK 13/14

A purely mineral bloom stimulator with 13% P2O5 and 14% K2O. Meant for one week around peak flowering, and the additive on this shelf most likely to write off your reservoir if you ignore the instructions.

One week maximum, and CANNA mean it

The directions are unusually tight. Add PK 13/14 three to four weeks before harvest, use it once flower formation is under way across the whole plant, and feed it for three to six days. No longer than a week.

CANNA address it head-on in their own FAQ: shops tell people it can be used for several weeks, and CANNA still say one. The reason they give is accumulation. Phosphate and potassium the plant does not take up stay behind in the medium, and after a week that starts counting against you rather than for you.

Which makes this product fundamentally different from a PK you feed all through flowering. It is a short, heavy intervention at a chosen moment, not a standing line in your schedule.

The dose has a condition, and it is almost always left out

Nearly every shop quotes 15 ml per 10 litres of tap water. CANNA attach a condition to it: provided the EC of your standard feed is not above 1.8 mS/cm.

That condition is the actual instruction. You are adding a substantial salt load to a solution already near the plant's tolerance, so the figure only holds if you have headroom. If your base feed sits higher, you have to bring it down before the PK goes in.

So measure again after adding, and measure both: CANNA specify checking EC and pH once PK 13/14 is in the tank.

What actually writes off a reservoir

Here is the real risk, and it is concrete. If the pH in the tank runs too high, above 7.0, phosphate and potassium precipitate as salt compounds that will not redissolve. CANNA call this saturation and are blunt about the outcome: the feed in the tank is finished and the tank has to be cleaned to prevent further precipitation.

There is one combination that raises that risk and that many growers make by accident. If you acidify with CANNA pH- Bloom, saturation can occur in exceptional cases, because that reducer is phosphoric acid based and so adds phosphate of its own to a tank already full of it. CANNA advise switching to pH- Grow, which works on nitric acid.

If you run a dosing computer, never put PK 13/14 into the B tank neat: undiluted it can destabilise the B feed and make it precipitate.

Available sizes

Technical Specifications:

• Type: mineral PK bloom stimulator, liquid
• Manufacturer: CANNA
• Composition: 13% phosphorus pentoxide (P2O5) and 14% potassium oxide (K2O)
• Timing: three to four weeks before harvest, once flowers have set across the whole plant
• Duration: one week maximum, in practice three to six days
• Dose: 15 ml per 10 litres, provided base feed EC is not above 1.8 mS/cm
• After adding: always re-check both EC and pH
• Avoid: pH above 7.0 in the tank, which raises the saturation risk
• Note: combined with pH- Bloom saturation can occur, use pH- Grow instead
• Substrate: soil, coco, rockwool and all hydroponic systems

Frequently asked questions

Can I feed it for longer than a week?
CANNA advise against it in as many words, because phosphate and potassium then accumulate in the medium. One week around the peak is the guidance.

Why must my EC be no higher than 1.8?
Because 15 ml per 10 litres adds a substantial salt load. Without headroom in your EC you go past what the plant can handle.

My reservoir has gone cloudy, now what?
Saturation has probably occurred. Those salt compounds will not redissolve: empty and clean the tank, or more will precipitate.

Can I use it with pH- Bloom?
That can cause saturation, because that reducer is phosphoric acid based and adds phosphate itself. CANNA advise pH- Grow, on nitric acid, instead.

Can it go in my dosing computer's B tank?
Never neat. Undiluted it destabilises the B feed and that precipitates.