How to Raise Roses in a Greenhouse
Few flowers give more pleasure in the greenhouse than roses. Roses tend to grow more vigorously in the greenhouse than outside and can flower up to three times a year. Undisturbed by wind and rain, the leaves can be clean and healthy and the blooms perfect. A single plant can continue to flower for 10 years or more. They can be planted in the greenhouse floor or in a deep pot or raised bed.
Select a spot for the rose that will allow for easy watering and full sun at least 6 hours a day. Mix equal parts compost and soil. Make a mound of the mixture in the pot, or dig a hole in the bed twice as wide as the root ball and make a mound in the center.
Remove roses from the shipping material. Cut off any broken or shriveled roots with pruning shears. Soak the remaining roots in a bucket of water for 6 hours.
Drape the roots over the mound of soil. Place the graft 2 to 3 inches above the soil line. Fill the pot or hole with soil, tamping it in place lightly as you fill. Water thoroughly and add more soil mixture if necessary.
Cut off any canes that are split or shriveled with the pruning shears. Remove canes from the center of the plant to allow air circulation and light to reach all the leaves. Select three to five healthy canes and remove the rest. Prune the remaining rose canes to 3 inches, making cuts just above an outward-facing bud.
Keep the greenhouse cool and well ventilated until the roses begin growing. Water whenever the top 2 inches of soil are dry.
Raise the temperature of the greenhouse to 70 degrees Fahrenheit after the roses leaf out. Warmer temperatures will speed growth, but temperatures that are too hot reduce flower life.
Fertilize with a complete rose fertilizer or compost tea after the plants leaf out and after each flush of bloom.
Cut spent blooms off with pruning shears just above the highest five-leaflet leaf below the bloom.
Prune severely in early winter. Select three to five healthy canes. Remove all others with the pruning shears. Cut the remaining canes to an outward-facing bud 4 to 6 inches above the graft.
Examine the plants daily for signs of insects or disease. Begin control measures as soon as problems appear.
- The graft can be identified by locating the bend on the trunk of the plant where the color or texture changes.
- Learn about IPM techniques to control insect and disease problems safely.
- Do not get water on the leaves when watering the plants. Overhead watering promotes the spread of disease.
Lynn Doxon has a Ph.D. in horticulture, is a retired cooperative extension specialist and teaches courses in urban farming. She is the author of three books: "The Alcohol Fuel Handbook," "High Desert Yards and Gardens" and "Rainbows from Heaven." Doxon wrote the Yard and Garden column for the "Albuquerque Journal" and numerous magazine and newspaper articles and cooperative extension service guides.