To begin, choose parents with many common strengths and no shared weaknesses. If one parent has a weakness, choose the other with a strength that balances it. Some varieties create poor offspring as the mother, but good offspring as the father, and vice versa.
Unless you live where the growing season is long, start your process during the first flush of flowers so the plant has the whole season to mature the seed.
1. Choose six or more buds on the mother rosebush. They should still be tightly closed.
2. Carefully remove the petals and anthers from several buds of the mother plant. Use nail clippers for this delicate task. (The anthers are the tiny stalks clustered in the flower center; the heads are where pollen is stored. The anthers should not be shedding pollen yet when you remove them.) A group of pistils in the center of the flower will remain. Cover the clipped buds loosely with a paper envelope so you can find them again and to keep out pollinating insects.
3. Let the prepared buds sit for one day. They will be ready to hybridize when the stigmas, or tops of the pistils, become shiny and wet. (Don't wait longer than two days.)
4. When the prepared buds are ready, remove an opened bloom from the father plant. (The anthers will be open and shedding powdery pollen.) Carefully snip off the petals; leave the anthers intact. Use this flower like a paintbrush to carefully dab pollen onto all of the prepared mother flowers. Cover again with the paper envelope. If you are successful, the base of the mother flower will swell into a rose hip, the fruit of the rose, within one or two weeks.
5. Leave the rose hips until they turn dark after a frost. Then harvest them and store them in a sealed plastic bag in the refrigerator until spring.
6. In spring -- a month or two before the last frost date -- cut the rose hips open, and plant the seeds in seed-starting mix or potting soil in a plug tray. Set the tray in a 70 to 75 degree F greenhouse or in a southern-exposure window. Keep moist and fertilize regularly with diluted balanced fertilizer.
7. The seedlings should grow big enough to bloom within six weeks. Choose the ones you wish to nurture into full rosebushes (probably less than 5 percent), and send the other scientific attempts to the compost pile. Pot the survivors in individual pots until they can be planted in the garden.
Over time, you'll discover other flaws, such as disease problems, lack of reblooming, or weak plants. From several hundred seeds, you may keep only one plant, depending on your taste, but it's your creation and the world has never seen its exact likeness before.