John Boyd’s 1969 The Pollinators of Eden is a standalone SF novel.
Doctor Freda Caron expects that when the starship Botany docks, her fiancé Paul Theaston will be on it. He isn’t; all she gets is a message and a sample of alien life. Paul is doing research on the planet Flora, where he has encountered an intriguing scientific mystery. He wants to stay on-planet for one more duty cycle. Although mildly put out (this means she’s saddled with planning their wedding all by herself, rather than allowing Paul to think he’s helping), Freda also understands why he would stay. She too is a professional botanist; she understands the appeal of this tulip-appearing enigma.
The tulip has a flower much like flowers found on Earth. There are no known insects on planet Flora. Why produce a flower, and pollen, when there is nothing to spread the pollen. Or is there? Who or what does the pollinating?