Alkaline-Tolerant Flowers

Zone 3 (Minus 40 Degrees F)

• Baby’s breath (Gypsophila paniculata) prefers well-drained sites with alkaline soil. This 18- to 36-inch tall perennial blooms with small white and pink flowers in summer. It thrives in sunny exposures and is hardy in zones 3 to 8.

  Candytuft (Iberis sempervirens) grows best in well-drained, alkaline soil and full sun. This perennial grows to 18 inches tall and blooms in spring with white flowers. Hardy in zones 3 to 9, candytuft looks best when cut back every other year.

  Dwarf delphinium (Delphinium grandiflorum “Summer Nights”) grows from 8 to 14 inches tall and is hardy in zones 3 to 7. This perennial blooms in spring with bright-blue flowers. It grows best in sites with full sun and well-drained, alkaline soil.

Zone 4 (Minus 30 Degrees F)

• Oregano (Origanum rotundifolia x scabrum) is hardy in zones 4 to 8 and prefers alkaline sites. This creeping perennial herb grows from 6 to 12 inches tall and has aromatic, edible foliage. It blooms with pink, white and green flower bracts and thrives in full sun.

  Pinks (Dianthus spp.) are hardy in zones 4 to 9 and grow from 6 to 24 inches tall. These pink-flowering perennials bloom from late spring to early summer and prefer sunny sites with well-drained, alkaline soil. Pinks need adequate air circulation to thrive.

Zone 5 (Minus 20 Degrees F)

• Lavender (Lavandula angustifolia) is hardy in zones 5 to 9 and grows well in full sun and well-draining, alkaline soils. This 2- to 3-foot tall perennial produces fragrant purple flowers in summer.

  Red valerian (Centranthus ruber) grows to 3 feet tall and is hardy in zones 5 to 8. A perennial, red valerian grows to 3 feet tall and produces spikes of bright-red flowers in spring. It grows well in poor, dry and alkaline soil and prefers full sun.

Annuals and Biennials

• Scabiosa or pincushion flower (Scabiosa atropurpurea) prefers alkaline soil. This annual flower blooms with blue, white, pink and purple flowers from summer through late fall. It grows to 3 feet tall and thrives in sunny sites with well-drained, fertile soils.

  Sweet William (Dianthus barbatus) also grows well in alkaline soils. This 8-inch-tall biennial self-seeds and produces aromatic, white and pink flowers in late spring.