Companion plants for Ninebark
Ninebark blooms from May through June. It wants full sun and moderate water. The 8 companion pairings below each state why the pairing works.
Blooming before Ninebark opens

Hyacinth
Shares full sun and moderate water; blooms in early spring, before this one opens; low at 10 in, to carpet the ground beneath; both offer pollinator forage, in different months.

Windflower
Takes full sun to part sun and moderate water; blooms in early spring, before this one opens; low at 6 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.

Eastern Redbud
Takes full sun to part sun and moderate water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 23 ft, for the layer behind it.
Taking over as Ninebark finishes

Black-Eyed Susan
Shares full sun and low to moderate water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.

Blazing Star
Shares full sun and low to moderate water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.

Sneezeweed
Shares full sun and moderate water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.

Crocosmia
Shares full sun and moderate water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; lower at 3 ft, for the front of the border.

Sunflower
Shares full sun and moderate water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.