Companion plants for Solomon's Seal
Solomon's Seal blooms from May through May. It wants part shade and moderate water. The 8 companion pairings below each state why the pairing works.
Blooming before Solomon's Seal opens

Hellebore
Shares part shade and moderate water; blooms in late winter, before this one opens; evergreen, so the bed keeps its shape through winter; both offer pollinator forage, in different months.

Eastern Redbud
Takes part sun to part shade and moderate water; blooms in mid spring, before this one opens; both offer pollinator forage, in different months; both are native plants.

Serviceberry
Takes part sun to part shade and moderate water; blooms in mid spring, before this one opens; both offer pollinator forage, in different months; both are native plants.
Taking over as Solomon's Seal finishes

Goatsbeard
Shares part shade and moderate water; blooms in early summer as this one finishes; taller at 3.9 ft, for the layer behind it; both offer pollinator forage, in different months.

Spiderwort
Takes part sun to part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; both are native plants.

Climbing Hydrangea
Shares part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; a soft color beside the yellow.

Northern Sea Oats
Shares part shade and moderate water; blooms in midsummer, extending the bed's season; its seed heads stand through winter, for structure and the birds; taller at 3.3 ft, for the layer behind it.

Summersweet
Shares part shade and moderate to high water; blooms in midsummer, extending the bed's season; both offer pollinator forage, in different months; taller at 5.9 ft, for the layer behind it.