If you want to grow cannabis, today you will find a variety of specialized fertilizers that are adapted to marijuana plants. In addition to these basic fertilizers, which contain the key ingredients for healthy plant growth and abundant flowering, there are plenty more products designed to enhance and promote the growth of cannabis plants. Starting with root stimulators, which promise a faster rooting of young plants into the medium, vitamins and hormones, there are flower stimulators that have a positive influence on the development of flowering. There are now many of these products in different composition and concentration. The classic among them is PK 13/14 (phosphorus / potassium), known for many years and used by many cannabis breeders. PK 13/14 has an undeniable effect and, if used correctly, can provide significant increases in yield. This is the blessing given by PK 13/14! On the other hand, PK13 / 14 can do exactly the opposite. Excessive addition of PK 13/14 inhibits flowering and prevents further plant growth. It is particularly tricky that different cannabis strains react very differently to the addition of PK 13/14. While some varieties graciously put away a possible overdose of the additive, it comes with other varieties first halted flowering. Unfortunately, this lost time can no longer be made up, as the flowering cycle does not lengthen when it stops, but the plant simply has fewer flowers at the end. This can be a loss of 20%, without really knowing why it was, because the plants actually look lush green, have great flowers and have no burns of over-fertilization. Another phenomenon of excessive PK 13/14 addition is gray mold in the flowers. Giving PK 13/14 over too long a period of time (even if it is relatively low) increases the likelihood of mold forming in the flowers at the end of the flowering phase, given otherwise good climatic conditions in the room. Use PK 13/14 with great caution. Do not take more than 1/3 of the manufacturer's recommended dose and do not give it more than five to a maximum of seven days. On hydro or coconut cultures, keep the EC value of the effluent in the eye, if possible. If he starts to overly increase, end the addition of PK 13/14. While giving PK 13/14, it is best to reduce the amount of fertilizer so that the EC value stays at the same level. Also important is the time of addition of PK 13/14. Pay attention to the development of your plants. The flowers should already be strong and have covered the shoot tips, but not yet be too compact. This stage is usually reached after the fourth to fifth week of flowering. If you begin a modest addition of PK 13/14 at this stage, this addition can work wonders!