The miniature rose is ideal for widow boxes and containers, as its tiny 1 ½-inch blooms add color and fragrance all summer. Although some varieties reach heights of 3 feet, the UC Davis Extension notes that some are no more than 6 inches in height, while the majority attain heights of 12 to 24 inches and spread to the same width. When grown in full sun, these hardy plants thrive in rich, well-drained soil. Most bloom continuously throughout the summer and require relatively little care other than watering and fertilizing.
Fill the window box three quarters full with loose, lightweight soil. A mixture of equal parts potting soil, compost, peat moss and perlite makes a suitable potting mixture for window boxes.
Position the miniature rose bush in the center of the window box to its original planting depth. Fill in around the roots with soil mixture and firm down with your hands.
Add trailing plants like white alyssum, blue lobelia or verbena. These graceful flowers cascade over the sides of the box and contrast well with the miniature roses.
Tuck in vining foliage such as English or German ivy, ivy geranium or other small-leafed vines.
Water thoroughly until water runs free of the bottom of the window box. Monitor the soil carefully and water whenever it feels dry 1 inch below the surface. Soil in window boxes dries quickly in summer heat. Your window box may need daily watering.
Apply water-soluble fertilizer once a week. The Texas A&M University Extension recommends mixing the fertilizer to one-quarter strength.
Deadhead blooms as soon as petals begin to fade to encourage new blooms. This prolongs the blooming season of your roses.
Remove the rose plants in late fall and pot in a large plant pot. Grow as a houseplant over the winter and return to the outside in the spring, once the danger of frost has passed. If window boxes are detachable, move the entire box inside.