How to deadhead dahlia 'mystery day'

Deadheading dahlia 'mystery day' genuinely pays off. Once a flower fades the plant starts pouring energy into setting seed, and removing it redirects that energy straight back into producing more buds. Keep on top of it through the season and you get a noticeably longer, heavier display; stop, and flowering tails off as the plant decides its job is done.

Follow the spent bloom down to the first set of healthy leaves or a visible side bud, and cut just above it. Cutting only the petals off leaves the developing seedpod behind, which defeats the point.

Every few days to weekly through the flowering season — the more regularly, the better the repeat.

Snipping just the faded petals and leaving the swollen green seedpod below. The plant still thinks it has set seed, so dahlia 'mystery day' slows down anyway.