|Photo from Ball Seed Company
In its first season, you enjoy endless bloom from planting til frost is common. Overwintering is typical, with a robust bloom in early summer. Yet, once June rolls around - they look spent like this:
Gather the spent flower stalks and cut back about 2-3 inches off the top, leaving about 4-5 inches of green growth.
This removes the seed heads and stalks, forcing new growth from the leafy area beneath.
|Hedge hog hair-cut!
This cut will initiate new growth, which will bear new flowers in a couple of weeks. I used an all purpose water soluble fertilizer, just to give it that extra boost.
It may look severe, but it will extend the bloom until frost.
I have overwintered Dianthus x barbatus for up to 4 years by doing this each year. After that amount of time, it generally fizzles out and I replant a new lot.