Visitors often ask what fertilizer I use. Sometimes they say: "I too have that rose in my garden, but it is not at all as lush and thriving as yours."
The answer to the question is that I never buy any fertilizer save for some bone meal. Instead I use what nature gives me free of charge: green mulch, which I produce with a lawn mover. The greater the number of different wild plants that end up in the green mulch the more minerals and other nutrients it contains. Meadowsweet (Filipendula ulmaria) is especially good. That plant grows abundantly around here.
A topping of about two inches of green mulch ensures that I do not need to weed, the soil stays moist and porous and worms and microbes love it. Perfect! The mulch should not be worked into the soil. If so it consumes nitrogen and so uses energy rather than adding energy to the soil. But leave it to the worms and other experts on working the soil and you'll soon realize that you need to add another layer of green mulch. I give my roses their last topping of mulch in early July. If they are fed later than that, their ability to prepare themselves in time for the coming hardships of winter is greatly reduced. Spreading tree ashes around their roots in August enhances their ability to endure cold winters.
The fact that I use only green mulch does not mean I have nothing to give my roses and other plants in early spring. Whatever can be put into the compost returns to the garden as additional soil in the spring together with some bone meal. The green mulch I cannot use after mid-July I put into air tight bags, squeeze the air out of the filled bags and close them tightly. In the spring I have perfect food for the garden. The bags need to be open for a few days before the wintered green mulch is used. I then work it into the soil around the roses and other plants. The wintered green mulch does not consume nitrogen.
In Sweden they have done research comparing the effects of different fertilizers or combinations of fertilizers. The result was that using nothing but green mulch produces the best results both in the flower beds and the kitchen garden. Cheap, ecological and efficient. What more can you ask for?