• Zones 1-14, 18-21, 27-43
• Full sun; flowers may fade in hot-summer climates
• Regular watering
Border phlox is deservedly popular for the showy, dome-shaped clusters of fragrant flowers it produces throughout the summer. Plants reach 2 to 4 feet tall and almost as wide, making a dramatic addition to the border. Leaves are dark green, 3 to 6 inches long; individual flowers are just about an inch across and come in a wide variety of colors.
Given the growing conditions it needs, phlox will reward you with healthy foliage and a long bloom season. Soil must be rich and well drained; dig planting beds deep and amend well with organic matter such as compost or well-rotted manure. Fertilize annually in spring. Deadhead spent blooms, since seedlings will not bloom true to the parent. Divide every 2 to 3 years, replanting only divisions from a clump's edges.
Powdery mildew can cause serious problems in hot, humid areas. To combat it, plant mildew-resistant varieties such as 'Ice Cap'. Cut mildew-infected plants to the ground each fall; then discard the cut-off portions and any debris.