- 1). Water the roses once weekly, providing 1 inch of water or enough to moisten the soil to a 6-inch depth. Apply water twice weekly during hot weather if the soil dries out quickly, as grandifloras do best in soil remaining evenly moist.
- 2). Spread a 2-inch layer of pine straw, bark or leaf mold on the ground beneath the grandiflora bush, leaving a space between the mulch and the rose's stems. The mulch prevents soil temperature fluctuations and helps retain moisture.
- 3). Fertilize grandiflora roses in monthly beginning from the first new growth in spring and continuing until September. Apply 3 tbsp. of 16-4-8 or another rose fertilizer blend to each rose bush. Sprinkle the fertilizer in a circle around the base of the plant. Water the area immediately after application.
- 4). Remove the old blossoms from the bush as they begin wilting. Cut back the stems to within ¼ inch of a five-leaflet set. Grandifloras produce more blooms with regular old flower removal.
- 5). Prune grandifloras lightly in late winter. Cut out any dead or damaged stems at the base with pruning shears. Dead branches develop a darker color than the live ones. Cut back overgrown branches to within ¼ inch of an outward facing leaf bud.
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