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; a soft color beside the white.
Taking over as Solomon's Seal finishes

Japanese Stewartia
Takes part sun to part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; stands well above at 16 ft, a canopy to plant beneath.

Meadow Rue
Shares part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; taller at 4 ft, for the layer behind it.

Wishbone Flower
Shares part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; lower at 10 in, for the front of the border.

Rhododendron
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.

Beautyberry
Takes part sun to part shade and moderate water; blooms in early summer as this one finishes; both offer pollinator forage, in different months; taller at 5 ft, for the layer behind it.

Goatsbeard
Shares part shade and moderate water; blooms in early summer as this one finishes; taller at 4 ft, for the layer behind it; both offer pollinator forage, in different months.