Many of the inexpensive miniature roses sold as florist’s gifts are varieties of Kordana roses. These inexpensive pots of roses have been developed for their ability to grow rapidly to flowering size and to withstand shipping and indoor conditions for the florist market. They aren't scented roses.
Not a Single Plant
Although the plants are small when you buy them, you may have as many as six separate plants in one 6-inch pot. The plants may have been treated with a growth retardant hormone to keep their growth in check. They may not remain miniature plants if you plant them outdoors (although their blooms will stay small).
Growing Mini Roses Indoors
The recommendations for indoor growth suggest growing them in a bright sunny window, but under these conditions the high peat content soils can dry out in a few hours, sending the plant into wilt.
All roses like humid/evenly moist but not wet soil. They prefer cool, not hot soils. If you place them in a window, use a cachepot to insulate the roots and keep them from overheating. A cachepot is an ornamental pot which holds the plastic pot the rose is planted in.
Most greenhouse soils are designed for constant drip watering, so your rose may dry out if it is not watered often. Peat-based soils will not absorb moisture easily once they dry out, and watering them from above will not help. To make sure your rose is not too dry, soak the pot in water for several hours to make sure the soil is completely moist. Then water it by allowing it to soak up water from the bottom of the pot rather than watering from above.
Improving the Soil
If your environment is very dry, you will have problems keeping the soil evenly moist. You can help the plant by adding some moisture holding crystals to the soil. These crystals are sold at florist’s shops and nurseries under several different names. superabsorber, hydrogel, water-absorbing crystal, Broadleaf P4, Soil Moist, Moisture Mizer, TerraSorb, Hydrosource, Watersave, Water Crystals, etc. You need less than a tablespoon of these crystals for a 6-inch pot. Poke a few holes in the soil with a pencil and drop in a few crystals to help keep the soil evenly humid.
Pests to Watch out For
Most mini roses are fairly disease-resistant but indoors they can suffer from mildew (a grey powdery substance on the leaves, which then turn yellow.) as well as from aphids and spider mites. Avoid overwatering and overfertilizing. Mist the plant once in a while to keep it humid and avoid spider mites. If it develops mildew, rinse the plant off and allow it to dry thoroughly. Clean the window sill or location where it developed mildew and allow that area to dry before replacing the plant in the same area. Make sure there is air circulation to avoid mildew. Other insects and diseases may attack them as well.
Keeping Them Healthy
To keep your miniature roses healthy make sure the soil stays moist, but not wet, give them a cool, light spot to grow, and remove all diseased leaves. Cut the flowers off after they have bloomed. Make sure the plant is in a site where there is good air circulation.
Use a slow release pelleted fertilizer for flowering plants scattered on the surface of the soil, or fertilize with a very dilute solution of flowering houseplant fertilizer every time you water.
After They Flower
When your roses have finished blooming for the first time, move them into a larger pot (or at least one pot per rose bush if there several in the original pot). You may need to keep moving them up towards a 5-gallon pot as a permanent home on a balcony or patio.
If the growth is long and weak, trim them back to a height of 3 inches from the soil height. If you move the roses to a larger pot, make sure the plant remains at the same height above the soil, don’t put the roots deeper in the pot then they were in their original pot.
Growing Them Outdoors
Kordana roses are hardier than many tea roses and can be grown in zones 5 to 9. In colder zones, they may need winter protection (mulch with straw and wrap with burlap/breathable wrap). If you plan on growing them in very cold regions, or areas with severe winter weather, you may want to trench them (dig a 12-inch deep trench, place your rose in it, roots and all, water and bury it with soil, replant in spring)
As these roses can be grown in large pots, you may just want to protect them from winter by moving the pot into an insulated, but cool and light garage, unheated basement, or shed where they will remain dormant.