“How and when do you pinch dahlias to encourage fuller growth?” Question from April of Dresden, Tennessee
Answer: Once your dahlias are close to their final height (which depends on the variety) and have ample foliage, you can pinch or trim them back to encourage fuller growth, more branching, and more flowers. Just be sure to wait until they are large and full enough to bounce back nicely.
I always recommend cutting them back just above a branching stem node (see adjacent image). New branching stems will arise from the node. I also recommend using sharp shears to do the job rather than pinching (Corona Flora Scissors work very well). Cleaner cuts help plants heal and revive more quickly.
Black Gold Horticulturist