I bought perennial dianthus and it blooms fine at first but as flowers die the whole stem starts turning brown and thus doesn't flower more. I tried cutting off flower part once dead. Not sure what I am doing wrong. My soil here tends to have clay. they are planted in nice sunny location. FYI cant grow roses or azalea here.
Many perennial dianthus have one main flush of bloom in the spring and that's all. Some types will rebloom sporadically if deadheaded right after bloom, but most just have foliage the rest of the summer.