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

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

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

Windflower
Takes part sun to part shade and moderate water; blooms in early spring, before this one opens; both are strong pollinator plants, and they feed in different months; lower at 6 in, for the front of the border.
Taking over as Jacob's Ladder finishes

Summersweet
Shares part shade and moderate to high water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; taller at 6 ft, for the layer behind it.

Cardinal Flower
Takes part sun to part shade and moderate to high water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; taller at 3.5 ft, for the layer behind it.

Ligularia
Shares part shade and moderate to high water; blooms in midsummer as this one finishes; both are strong pollinator plants, and they feed in different months; taller at 4 ft, for the layer behind it.

Northern Sea Oats
Shares part shade and moderate water; blooms in midsummer as this one finishes; its seed heads stand through winter, for structure and the birds; taller at 3.5 ft, for the layer behind it.
Blooming alongside

Azalea
Shares part shade and moderate water; opens in mid spring and overlaps into this one's season; both are strong pollinator plants; evergreen, so the bed keeps its shape through winter.