I think it is too late for these plants to fertilize in the spring. The main dose of nutrients, for the spring start, should get much earlier. If organic fertilizer, then I give in the fall. If mineral fertilizer or ash, then on the snow. I don’t fertilize in the spring.
I have very heavy deep clay soil. Holds moisture well. But when planting, I have to dig the soil properly and add a lot of compost to each plant, because I don’t interfere with the soil after that. By no means do I dig.
I do not add peat, but only quality own compost. Too much peat will greatly lighten the soil, which becomes prone to drought. Peat has few nutrients and finds it difficult to absorb water when dry. With very light soil, it is very difficult to absorb soil moisture. Sandy soil is also not suitable for these plants.
Naturally quite a shallow spice and therefore they need to be provoked by nutrients to make the roots a little deeper and therefore I give them a lot of compost at the bottom of the pit and around the plant.
If this is not done, mulching with organic material initially helps, but later the plants begin to form roots at the top just below the mulch and are then more sensitive to drying, which stops growth. Subsequently, over time, each mulch begins to overgrow the weeds we are trying to pull out, making the situation worse. Someone puts a lot of mulch under the plant and a haystack effect can be created when the water pours out of the root of the bush and it is difficult to judge whether the soil at the roots is sufficiently moist.
It is often difficult to guard damp substrate under bushes. Naturally, they form thickets themselves, thus protecting their roots from drying out. If we want to have spacing between plants, we must protect their roots from the sun and thus dry out.
I have been growing these plants for more than 22 years and I have found that it is best to guard the coolness and moisture of the substrate at the roots with agrotextiles. I often mulch with organic material, but at the same time I cover it with agrotextiles.
The principle is similar to a greenhouse. Light passes easily through the glass, but the heat has a problem escaping.
Similarly, water passes easily through the agrotextile, but water vapor has trouble escaping. It is wetter there and after watering, this climate stays at the roots for longer, which they like very much. I even cover with a second layer of fabric to make the effect even greater.
They need to have the root system cool and moist with enough compost and thus gradually releasing nutrients. And of course enough sun - head in the sun and feet in the shade.
They do not like windy places and do not tolerate very dry winds for a long time. They need to be protected from strong winds.
And a stable winter with plenty of snow and therefore moisture is a prerequisite for them to grow and give birth