The best time to chop your dahlias to keep them from becoming too leggy is in late May or early June when they are 12-18 inches tall and have at least 2 sets of true leaves. Cut off half to a third of the height just above a leaf joint to encourage side branches. If you are doing it later, choose stems that aren’t flowering or only have a few buds so you don’t lose too many future flowers. Depending on your location you only have until the end of summer for the plants to rebound which is why timing is critical. If frost is not an issue in your zone go ahead and give them a haircut.
The best time to chop your dahlias to keep them from becoming too leggy is in late May or early June when they are 12-18 inches tall and have at least 2 sets of true leaves. Cut off half to a third of the height just above a leaf joint to encourage side branches. If you are doing it later, choose stems that aren’t flowering or only have a few buds so you don’t lose too many future flowers. Depending on your location you only have until the end of summer for the plants to rebound which is why timing is critical. If frost is not an issue in your zone go ahead and give them a haircut.