Virtually all plants will bloom longer if you deadhead them. Picking lots of blossoms encourages the plant to branch and so you get more. I’ve had especially good luck with these varieties: Heliopsis (False Sunflower), which sometimes blossoms for 10-12 weeks in the fall Rudbeckia (Black Eyed Susan) – 6-7 weeks Monarda (Bee Balm) - 8-12 weeks Coreopsis - 8-12 weeks Bleeding Heart (Dicentra) ‘Luxuriant’ - 10-14 weeks, Feverfew – 8-12 weeks if you let new plants grow and cut back the old ones
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