Plant the rose bush seeds approximately ¼ inch deep in a seed-planting mix in seedling trays or your own planting trays. The trays need not be more than 3 to 4 inches deep for this use. When planting rose seeds from various rose bush hips, I use a separate tray for each different group of seeds and label the trays with that rose bushes name and planting date.
Cover the stem with plastic or a mason jar. To cover the stem with plastic, insert two eight-inch (20-cm) sticks or wires into the soil on either side of the stem to prop up the plastic. Cover the pot and stem with a clear plastic bag, and affix the bag to the pot with an elastic or twine. With a mason jar, simply place a large mason jar over the stem.
Español: cultivar rosas usando semillas, Italiano: Coltivare le Rose Usando i Semi, Português: Cultivar Rosas a Partir da Semente, Русский: вырастить розы из семян, 中文: 用种子种玫瑰, Deutsch: Aus Samenkörnern Rosen ziehen, Français: faire pousser des roses à partir de graines, Nederlands: Rozen kweken uit zaad, Bahasa Indonesia: Menanam Bunga Mawar dari Biji, العربية: زراعة الورود من البذرة, Tiếng Việt: Trồng hoa hồng từ hạt, 日本語: バラを種から育てる, 한국어: 씨앗으로 장미 기르는 방법
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.
Remove the seeds from the fridge. Try to do this around the time that the seeds would normally start to germinate, such as in early spring. Make sure that the environment outside of the fridge is about 70 degrees Fahrenheit. The seed will not sprout until you take them out of the fridge. Depending on the rose variety and individual seeds, the seeds could take anywhere from four to sixteen weeks to germinate. Often, 70% or more of the seeds never sprout at all.
Please keep in mind that many rose bushes are grafted rose bushes. This means that the bottom part is a hardier rootstock that will withstand cold and heat better than the top and more desired part of the rose bush. Starting a rose bush from cuttings places the new rose bush on its own roots, so it may not be as hardy in cold climates or in extreme heat conditions climates. Being on its own root system can cause the new rose bush to be far less hardy than its mother rose bush.
One way to stratify the rose seeds is to place the cleaned seeds on a paper towel (a heavyweight brand such as Bounty). Then moisten the paper towel with a solution of half & half purified water and peroxide (to help prevent mold). Fold the paper towel closed, encasing all the rose seeds in the moistened paper towel. Then place the towel full of seeds into a plastic zippered bag. Mark the seed variety and date on the outside of the plastic bag with a permanent marker, and then place the bag into the refrigerator set at about 34-38 degrees. Never freeze the seeds, and do not let them dry out. The moistened paper towel should remain moist in the closed plastic bag for many weeks.
The Baggie Method: This was the first method I ever tried. Here you fill 2-inch plastic pots with potting soil, insert the rose stem halfway inside the pot, then put the pots into a one-gallon plastic zip-lock bag. You can get four 2-inch pots into each gallon bag. I didn't like this method because it caused many of the cuttings to rot since the bags tended to fold over and therefore prevented the air from circulating. The success rate of this method is not very good. It may be helpful to place a couple of small sticks inside the bag to help keep it upright and full of air.
Black Spot: Rose plant leaves with black spots that eventually turn yellow have black spot. This is often caused by water splashing on leaves, especially in rainy weather. Leaves may require a protective fungicide coating, which would start in the summer before leaf spots started until first frost. Thoroughly clean up debris in the fall, and prune out all diseased canes.