My grandmother had several bushes in her backyard, both purple and white, but mainly you find purple. Lilacs grow in the spring months. Their blooms only last about a month and then they go away to come back the following year. I loved growing up with lilacs. Surprisingly, I don't use them much in my writing.
Flowers are very inspirational in romance writing. I like using roses, jasmine (do they count?) gardenias, and lavender. I don't use lilacs simply because they are seasonal and very rarely do one of my romance stories take place in the spring.