Baby's breath (Gypsophila paniculata) was a type of flower often added to rose bouquets.
In 2327, Q, pretending to be a delivery man, brought a bouquet of roses and baby's breath to "John Luck Pickard". (TNG: "Tapestry")
In 2375, The Doctor gave Seven of Nine a bouquet of roses and baby's breath as a sign of his affection for her. (VOY: "Someone to Watch Over Me")