Helping hydrangeas bloom

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Q: I have two hydrangea plants that seem to have stopped flowering. Am I pruning them at the wrong time? They are both facing south and?the green leaves are very plentiful.

Hydrangeas are an interesting genus in that there is so much diversity between the species. The first thing you’ll need to know is the variety or category of hydrangea you have. Care and maintenance will vary depending on this, particularly when it comes to pruning. Having a hydrangea appropriate for your zone is also important. A variety that is out of zone tolerance may experience much die-back from the cold if unprotected and will re-grow from the crown but is unlikely to blossom that season.

All hydrangeas prefer a moderately bright location, ideally with morning sun and afternoon shade. Hydrangeas have so much leaf mass that when exposed to the hot afternoon sun they transpire and exhaust themselves. They prefer growing in a cool moist soil, and a spring mulching annually will assist in soil-moisture retention.

Pruning incorrectly or at the wrong time of year can prevent blooming. The two most popular categories are Hydrangea macrophylla (the mophead varieties – usually pink or blue – with the big round flowerhead) and H. paniculata (PG) with its cone-shaped flowerheads. The macrophylla group blooms off old wood (stems that have been on the plant since the summer before the current season). I suggest removing stems with the old blossoms from that season down to approximately 15 cm (6 in.) from the crown of the plant. Leave stems that have no blossom unpruned, as they carry the flower buds for the following year. The paniculata (PG) group is a much easier and less complicated pruning task. Come late fall pruning should be harsh. I take mine down to approximately a crown the size of a basketball. This family blooms on new growth from the current season, so nearly all the new growth from a sturdy base will produce a flower bud.