Fertilisation can be carried out either with natural fertilisers as well as with complex chemical fertilisers.
If using organic fertiliser (like guanito), it must be given in November.
If, however you use a chemical fertiliser, it can be administered in January. Before flowering time, in the second decade of March, it is good to fertilise using products with a low sulphur content but high in phosphorus and above all in potassium (for example 5-12-12), necessary for producing plenty of blooms. A composition with too much sulphur makes the plant produce thick foliage, to the detriment of the size and number of flowers;
moreover excessive and early foliage production, in the event of late snows, could weigh down the plant and cause the woody branches to snap.
Peony plants with one, two or three branches require a quantity of two teaspoons of complex chemical fertiliser to be sprinkled around the plant without touching the trunk. This quantity must be increased based on the number of the branches and the overall size of the shrub. The operation can be repeated in autumn (before the rains) and interspersed, every three or four years, with a compost fertiliser, again avoiding direct contact with the plant.