Companion plants for Dianthus
Dianthus blooms from May through August. It wants full sun and low water. The 8 companion pairings below each state why the pairing works.
Taking over as Dianthus finishes

Goldenrod
Shares full sun and low water; overlaps, then carries the display into mid fall; its seed heads stand through winter, for structure and the birds; both offer pollinator forage.

Autumn Joy Sedum
Shares full sun and low water; overlaps, then carries the display into mid fall; its seed heads stand through winter, for structure and the birds; both offer pollinator forage.

Aster
Shares full sun and low to moderate water; blooms in early fall as this one finishes; both offer pollinator forage, in different months; its seed heads stand through winter, for structure and the birds.

Switchgrass
Shares full sun and low water; overlaps, then carries the display into mid fall; its seed heads stand through winter, for structure and the birds; both offer pollinator forage.

Pampas Grass
Shares full sun and low water; overlaps, then carries the display into mid fall; its seed heads stand through winter, for structure and the birds; stands well above at 8 ft, a canopy to plant beneath.

Little Bluestem
Shares full sun and low water; overlaps, then carries the display into early fall; its seed heads stand through winter, for structure and the birds; taller at 3.5 ft, for the layer behind it.
Blooming alongside

Grape Hyacinth
Shares full sun and low water; blooms in early spring, before this one opens; lower at 8 in, for the front of the border; both offer pollinator forage, in different months.

Rosemary
Shares full sun and low water; opens in early spring and overlaps into this one's season; evergreen, so the bed keeps its shape through winter; both offer pollinator forage; they only overlap in zones 8 to 9.