“What are the best cut flowers or the most dependable flowering plant to give my valentine?”
My answer depends of how you define “best” or “dependable.” For cut flowers, you may consider mini-carnations. I received a vase of mini-flowered carnations, leather-leaf ferns, and baby's breath (small white flowers often used as in bouquets). With daily water change and flower grooming, the arrangement lasted three weeks.
Note that the color red is in high demand for Valentine’s Day and other colors of (especially roses) should be considered.
Since the early 18th century, The Language of Flowers was used to send messages by the selections of flowers and their colors. Pansy said “thinking of you;” cactus indicates warm feelings, rosemary said remember, and shamrock spoke of joy. Whether the flower was in bud, fully open, or faded modified the message as did the flower color: white spoke of purity, red of passion, and each shape and tone add to the dialogue. It is hoped that the sender and receiver are using the same language.
Perhaps the time has come for you to develop your own Language of Flowers. Have fun.
“Best” flowering plants certainly would include African violets, peace lilies, cyclamen and orchids. Blooms come and go, foliage is stable and permanent. Look for plants with white-variegation in their leaves. Consider coleus with fancy color patterns that reflect the rainbow or sing in one or two colors.
If you make selections at this time of the year of particular colors or form of coleus, cuttings can be easily rooted throughout the late winter and early spring to multiply plants for use in pots, window boxes and garden beds. Turn your Valentine’s Day gift into a summer-long display.