Phosphorus and potassium are essential elements for plants. Phosphorus is necessary for root formation and influences respiration and photosynthesis. Phosphorus is therefore essential for energy transport in the plant. Phosphorus also plays a significant role in flowering and ripening. Potassium is necessary for the absorption and transport of nutrients in the plant. For example, it regulates the opening and closing of stomata. Potassium also plays a role in plant strength and quality. On the other hand, potassium has a beneficial effect on the moisture release of leaves and on ripening.

With the flowering stimulator PK 13-14, the plant receives a relatively large amount of phosphorus and potassium for three to four days. This creates an optimal level of aridity, which stimulates the formation of flowers.