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

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

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.

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; its white flowers settle the white.
Taking over as Solomon's Seal finishes

Rosebay Rhododendron
Shares part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; evergreen, so the bed keeps its shape through winter.

American Wintergreen
Shares part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; evergreen, so the bed keeps its shape through winter.

Northern Sea Oats
Shares part shade and moderate water; blooms in midsummer, extending the bed's season; both offer pollinator forage, in different months; its seed heads stand through winter, for structure and the birds.

Blue Wood Aster
Shares part shade and moderate water; blooms in late summer, extending the bed's season; both offer pollinator forage, in different months; its seed heads stand through winter, for structure and the birds.

Woodland Stonecrop
Shares part shade and moderate water; overlaps, then carries the display into early summer; evergreen, so the bed keeps its shape through winter; both offer pollinator forage.