Remove the rose hips once ripe. The rose hips will start out small and green, then change color as they grow until they are completely red, orange, brown, or purple. You may pick them at this point, or wait until they are just beginning to dry out and wrinkle. Don't wait until they are fully dry and brown, as the seeds inside may have died by this point.
Fertilizer: Roses are heavy feeders, and will benefit from a steady supply of nitrogen, phosphorus and potassium. You can provide these nutrients with either liquid or granular fertilizers, at a ratio of approximately 5-8-5. In most cases, regular applications of compost, rotted manure, fish emulsion and seaweed extracts will provide roses with all the nutrients they need. These organic amendments also help to moderate pH imbalances and stimulate beneficial soil life. Other organic amendments favored by rose growers include greensand, black rock phosphate and alfalfa meal.