The USDA hardiness zone of 5b incorporates the area around Columbia, Missouri and Mansfield, Pennsylvania. Zone 5b reflects the average minimum temperatures of -15 to -10 degrees F in winter. The difference between 5a and 5b is a mere 5 degrees F in minimum temperature average. The best flowers to plant in zone 5b are hardy in weather that gets very cold.
Knock Out Rose
The knock out rose, Rosa Radrazz, is from the rose family. It is a fragrant fast growing and easy to grow shrub. This very hardy rose gets 4 feet tall and 3 feet wide blooming all season. Grow a knock out rose in partial shade or full sun. They are drought tolerant. Propagation is restricted because they are patented and must be purchased.
The swamp mallow, Hibiscus moscheutos, is from the mallow family. It is a wetland perennial that gets 7 feet tall. Velvety leaves are 6 to 8 inches long and 2 to 3 inches wide. Flowers are 6 inches wide and white or pink. Grow swamp mallow in good moist soil in full sun. Propagate via root division or by seed.
The garden sage, Salvia officinalis, is from the mint family. It is a fragrant perennial shrub that can be in container gardens. It will get 2 feet tall and 2 feet wide. Leaves are 3 inches long and grayish green. Leaves smell like lemons. Flowers are white, blue, or lilac and on racemes. Grow garden sage in full sun with regular pruning. It can be drought tolerant. Propagate via seed, stem cuttings, leaf cuttings, or by division.
The pruneleaf azalea, Rhododendron prunifolium, is from the heath family. It is a shrub that can be shaded. It will get 6 to 8 feet wide and 10 to 15 feet in height. Flowers are in the summer and can be red, orange, or pink. Flowers are 2 inches long, funnel shaped and in clusters. Grow a pruneleaf azalea in morning sun with afternoon shade. Soil should be sandy moist and acidic. Propagate via seed, semi-ripe cuttings in fall, or spring stem cuttings.
The white gaura or whirling butterflies, Gaura lindheimeri, is from the evening primrose family. It is easy to grow, a perennial and drought tolerant. This gets 2 to 4 feet tall with 2 to 3 feet width. Leaves are 1 to 3 inches long. Flowers are inch wide and white at the start going to rose pink at the day's end. Stalks are slender and hairy. Plant a whirling butterflies in full sun or partial shade in well drained soil. Propagate via seed or by clump division.