deadheading phlox and snapdragons

Question

Should I clip the entire stem beneath the spent flowers?

Answer 1

Cut off spent flower clusters as soon as the flowers begin to wither with a pair of small shears. …
Cut off the entire flower spike once all the buds have bloomed and there are no new buds forming along the stem. …this goes for both flowers!

Answer 2

Dead-heading phlox down to the basal leaves once all the bloom buds have opened. This will keep it from self-sowing everywhere but is a matter of personal preference, not plant health. Snapdragons often continue to make new flower buds on old flower stems so don’t be eager to cut them down. Watch and maybe trim back that one cluster that is done blooming but only back to where it meets the flower stem. In fall let snapdragons go to seed and you will have more next year although flower color may change over time. Snapdragons are half-hardy which means they may live through winter. In the north, this is more likely if there is good snow cover. More on snapdragon care here: https://www.gardeningknowhow.com/ornamental/flowers/snapdragon/growing-snapdragon.htm