Short answer: PK 13-14 is a flowering stimulator with NPK 0-13-14. You add it to your main fertilizer from the first week of flowering until a week before harvest. The product page gives 2-6 ml per 10 litres of water. Build up in steps and follow your feeding chart.
PK 13-14 is used in cannabis grows and in other flowering plants. This guide explains what it contains, when to start, how much to use, and where growers go wrong.
What is PK 13-14?
PK 13-14 is a stimulator made from food grade minerals. It has an NPK value of 0-13-14 and a concentration of 1:1500. That means it has no nitrogen, and it supplies phosphorus (P) and potassium (K) only.
A stimulator is not a main fertilizer. It does not feed your plant on its own. You always use it together with a main fertilizer, such as a Supermix for your substrate.
What does PK 13-14 do in flowering?
Phosphorus supports the root system and the development of flowers. Potassium helps the plant move water and sugars around during flowering. In flowering your plant needs less nitrogen and relatively more P and K.
A main fertilizer already contains some P and K. PK 13-14 adds more of both, so you can raise the P and K level without raising nitrogen. This is why growers add it when the plant starts to make flowers.
When to start PK 13-14
Start in the first week of flowering and continue until the final week. Stop about a week before harvest, in the last rinse week. The feeding chart shows no PK 13-14 in that final week.
The product page also gives a tip for the growth phase: 1 to 2 ml in 10 litres of water in the second week of growth can support faster root development. This is optional.
How much PK 13-14 to use
The product page gives these ranges. Your exact dose per week is in the feeding chart for your substrate.
| Situation | Dose of PK 13-14 |
|---|---|
| Optional root support, second week of growth | 1-2 ml per 10 litres of water |
| Flowering, start of flowering until a week before harvest | 2-6 ml per 10 litres of water (build up following the feeding chart) |
| Final week before harvest | None, see the feeding chart |
| Phosphorus or potassium deficiency (irrigation or foliar spray) | 2.5-5 ml per 10 litres of water |
In the Soil, Autoflower and Hydro feeding charts the dose rises step by step during flowering and is lowered again in the last weeks. For the exact amount per week, open the Bionova feeding charts.
The charts allow you to change doses in steps of 10% more or less. All EC values in the charts are measured with reverse osmosis water at EC 0.0. Your tap water has its own EC, so measure your solution.
How to mix PK 13-14 with your nutrients
- Fill your container with water.
- Add your main fertilizer first, for example the Soil Supermix.
- Add PK 13-14.
- Adjust the pH. The feeding charts give pH 6.0-6.5 for soil and autoflower, and 5.5-6.0 for hydro. For coco the chart gives 5.5-6.5.
If you use Silution, add it after the water and wait 30 minutes before adding the main fertilizer and stimulators. PK 13-14 can be mixed with all Bionova fertilizers, stimulators, minerals, universals and substrates.
PK 13-14 by substrate
The product page says to use PK 13-14 with a Supermix: Soil, Hydro, Aero, Autoflower or Longflower. Hydro growers can combine it with Nutri Forte A+B. Check the chart for your substrate and keep the same steps in dose.
Autoflowers move fast, so follow the Autoflower chart and do not copy a dose from a photoperiod chart. For long flowering plants, extend the schedule from mid flowering, as the Soil chart advises.
Common mistakes with PK 13-14
Starting too early. It is a flowering stimulator. Wait for the first week of flowering, unless you use the small optional root dose in growth.
Using it as a main fertilizer. PK 13-14 has no nitrogen and no calcium or magnesium. It does not replace your main fertilizer.
Going straight to the maximum dose. Build up over the weeks. A high dose in the first flowering week does not match the chart.
Ignoring pH and EC. A pH that is too high or too low blocks nutrients. The product page notes that phosphorus and potassium problems often come from poor substrate or a wrong pH, not from a lack of product. Check pH before you raise the dose.
Not stopping before harvest. The product page says to use it until a week before harvest.
Products mentioned
The stimulator in this guide is Bionova PK 13-14. If you want a set of flowering products to start with, look at the Bloom Booster Pack. You can see more products in the stimulators collection.
New to soil? Read our guide to living soil first.
FAQ
What is the PK 13-14 dosage?
The product page gives 2-6 ml per 10 litres of water in irrigation, from the start of flowering until a week before harvest. The exact amount per week is in the feeding chart for your substrate.
When do I use PK 13-14?
Use it from the first week of flowering. Stop in the final week before harvest. There is also an optional low dose of 1-2 ml per 10 litres in the second week of growth for root development.
Can I use PK 13-14 with autoflowers?
Yes. The Autoflower feeding chart includes PK 13-14. Use the Autoflower chart for the weekly doses, because autoflowers have a shorter cycle.
Can I use PK 13-14 as a foliar spray?
Yes. The product page says it can be used as irrigation and as foliar spray. For a deficiency, it gives 2.5-5 ml in 10 litres of water. Spray with care and see the product page for details.
