The Only Time It’s Ok To Cut Panicle Hydrangeas In The Fall

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The Only Time It's Ok To Cut Panicle Hydrangeas In The Fall

Pruning hydrangeas is essential to prevent them from becoming too woody and encourage them to produce bigger blooms. However, pruning incorrectly can affect the flowering of your plant. Panicle hydrangeas should be pruned in early spring since they flower on the current year’s growth. When new growth starts to emerge on the stems, you can see precisely where the buds are alive, and you can also see the size of the buds. This means that the bigger the bud you cut back to, the stronger and more vigorous the growth that comes out of it will be. Therefore, you can make a more informed pruning decision when pruning in spring.

You may choose to leave the faded flowerheads over winter as they add charm to your garden and interest when other plants have died back. Alternatively, you may prefer to leave the plant as a shelter or playground to encourage birds and wildlife to visit. However, cutting panicle hydrangeas back in the fall can also be beneficial for the plant. For instance, when there are no buds on the branches or when the weight of snow and ice could potentially damage the plant. Heavy snow and ice may settle or form on the panicles, weighing them down and resulting in unsightly bent or snapped stems. Therefore, if you’re expecting extreme weather, pruning back in the fall may be your best option.

How to prune panicle hydrangeas in the fall

hydrangeas with snow

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Before pruning, make sure the plant is completely dormant, meaning it has lost all of the leaves. Dead leaves should come off the plant really easily. If the plant isn’t completely dormant, pruning can stimulate new growth during a warm snap in the fall. Remove anything that is decayed.

To prune, you simply shorten back the branches by about one-third of their total length, making sure to cut above a bud. With branches that have several stems coming off them, you can either take off each stem individually, or take the whole main branch back to a bud. When cutting back old stems, make sure to leave around four pairs of buds on each one, as this will encourage more vigorous new growth, resulting in bigger flower heads.

To keep a more classic shrub shape, cut all shoots to a 6-inch stub with about two sleeping eyes — the dormant buds that look like raised dots under the bark. They are where your new shoots will sprout from.

Don’t confuse panicle hydrangeas with bigleaf hydrangeas

panicle hydrangeas in bloom

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It’s important not to confuse panicle hydrangeas with bigleaf hydrangeas. Panicle hydrangeas have, as the name suggests, ‘panicles’, which are loose branching clusters of flowers with the separate flowers attached by short equal stalks at equal distances along the central stem. Hydrangea macrophylia, also known as bigleaf hydrangea, is the more common variety of hydrangea plants. In comparison, this species shouldn’t be pruned much at all. When it goes dormant, it looks like it should be cut back, but if you do, you will be cutting off the formed flower buds for the following summer, which would be a real shame!

Garden expert Leigh Clapp offers the following advice on deciding when to prune different varieties of hydrangea: “Prune ones that bloom on old growth — lacecap, mophead, and oakleaf — after flowering, and in spring or fall for ones that bloom on new growth — paniculata and arborescens” (via homesandgardens.com.)

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Dr Heidi Parkes

By Dr Heidi Parkes

Senior Information Extension Officer QLD Dept of Agriculture & Fisheries.