A recent question from a guest was:

“I have heard that some hydrangea can be trimmed and some can not. I cut back one years ago and it never once flowered. Any answers?”

In response we are talking about “Mop Head” or “Big Leaf” Hydrangeas and also “Hardy Hydrangeas” or paniculata varieties.

Hydrangea ‘Limelight’ PP12,874 is best if pruned in late fall or early spring. Blooms on new wood. Make sure to prune off spent flowers when they turn brown. The paniculata or hardy varieties such as Pinky Winky, Little Lamb & Limelight bloom on new wood and can be trimmed in the late fall or early Spring.

Most “Big Leaf” varieties form their flower buds in the late summer for the following year. They should only be pruned when the flower heads begin to fade, otherwise you’ll risk removing next year’s flowers. When pruning, remove spent flower heads and prune back other shoots to encourage branching and fullness. As a rule of thumb for zone 6, you should not trim these Hydrangeas after August 1st.

In your case, your plants are experiencing what is called winter kill. The winters are too cold and are killing off the buds that have formed on the previous season’s growth. The plant is not dying as it is coming back from the base, but the new growth will not produce the flowers for you. I have heard of people putting rose cones over them or burlap around them and stuffing leaves over the top of the plant. If this sound like too much work, there are a few “Big Leaf” varieties such as Let’s Dance Moonlight and Let’s Dance Starlight that bloom on new and old growth. This means that if the same thing were to happen with these plants, you would still see flowers.

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