Cucumbers that have undergone early, direct-seeded plantings are on their second leaf.
(Cucumbers; have undergone; early, direct-seeded plantings) (Cucumbers that have undergone early, direct-seeded plantings; are; on their second leaf)
Cucumbers Cucumbers that have undergone early, direct-seeded plantings
have undergone are
early, direct-seeded plantings
on their second leaf