Answer: The most commonly grown hydrangea (big leaf hydrangea) produces flowers on new shoots which grow from old wood. If you pruned down to the ground or if your hydrangea freezed down to the ground each winter, you may never have flowers because there is no old wood for new flowering shoots to develop on. If this is the case, you may have to replace your hydrangea with a cultivar that blooms on both old and new wood. This way you're always assured of flowers every year. Endless Summer is such a cultivar.
St. John's Wort flowers on new growth and flowers best in full sunshine. Pruning in the fall should not affect the following year's flowers. Too much nitrogen can result in lots of lush growth at the expense of flowers so don't fertilize your St. John's Wort. Aside from watering once a week and making sure your plants get lots of sunshine, there's not much you can do to promote flowering.
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