Rose hips are the fruit that develops on the stem of a rose where the bloom once flowered and then faded. When flowers are harvested or deadheaded, rose hips do not develop so they can be a rarity to see. The hips contain hundreds of small seeds that carry the genetic material of the rose. In nature, the hip matures and ripens, and is then eaten by animals or falls to the ground and releases its seeds in situ. Ripe hips can be directly planted into soil, but successful germination cannot be guaranteed and the process can be slow. Alternatively, seeds can be harvested from the rose hips to speed up the germination process if only slightly. Roses grown from seed can take many years to develop and mature to the point of bloom, so this is not the preferred means of propagation.
Bury ripe and soft rose hips 1 to 2 inches deep in rich moist soil. Keep the soil evenly moist but not wet, and be patient. Whole rose hips when planted will first need to degrade and the seed germinate before you see any signs of growth. This process may take several seasons or several years. Plant one or two rose hips every few inches to increase the odds of success and thin any plants that develop as needed.
Harvest rose seeds from the rose hips when they are bright with color and beginning to soften. This is typically in the late summer or early fall in most climates. Break away the colored flesh to expose the rose seeds, and rinse the residue of the fruit off of the seeds with tepid water. This is best done over a fine mesh strainer. Lay the seeds out to dry in a single layer over paper towels layered over newsprint.
Stratify the rose hip seeds to break down the seed coat and speed germination by storing in a container partially filled with damp, clean sand. Leave the container with the seeds and sand in a location where it will receive ambient temperatures between 80 and 90 degrees Fahrenheit for 21 days or so. The top of a refrigerator often works well. Keep the sand damp. Collect the seeds from the sand and store in an airtight glass jar or ziplock bag in a cool place with low to no light until spring.
Plant the seeds in a sunny locale in nursery trays indoors or directly into the garden soil in the spring after the last frost has passed. Over-sow the seeds and thin excess seedlings later to increase the chance of success. Tent the seeded area with a clear plastic bag for a makeshift greenhouse, or use a garden cloche to create a protected and humid environment.
Remove the tent or cloche for a few hours each day when green shoots spring up to an inch or 2 in height. Gradually increase the time without cover over a period of a few weeks to slowly harden off the rose seedlings. Water regularly to keep the soil moist. Begin feeding the seedlings when they reach 3 inches or so with a very diluted fertilizer solution mixed with water at ¼ of the recommended dose.