Answer: What you have read is true; deadheading, or removing spent flowers, will stop seed production and the plant will then have more energy to produce more flowers. This is true for most perennials, however some will have only a single flush of blooms each year so deadheading is more of a way to keep the plant looking neat and attractive than it is to encourage additional blooms. I'd prune off any dead flowers and dead stems and branches, too.
Enjoy your garden!
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