Answer: Ask a hundred professional rosarians that question and you will get a hundred answers! There is no perfect rose fertilizer and no magic fertilizing schedule.
Depending on the levels of the various nutrients in your soil, your best choices will likely either be a 3-1-2 ratio product (such as 15-5-10) or a 1-1-1 ratio product (such as 10-10-10). You won't go wrong with either choice. Give your plants about 1 to 1 1/2 cups per 50 square feet in March and repeat it again at the lighter rate at 6 to 8 week intervals through the season, stopping in late August.
Compost is always a good choice to build the soil and add some nutrients. Late fall to late winter is a good time to add an inch or two of compost to the soil surface.
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