10 Plants You Should Never Cut Back in Fall

Avoid the most common pruning mistakes by not cutting these shrubs and perennials back in fall.

Cutting back plants at the right times can encourage fresh growth and increased flowering, and it can even reduce common plant diseases like powdery mildew. However, pruning plants at the wrong time of the year can actually inhibit flowering and cause other issues. When cleaning up your garden at the end of the growing season, knowing what perennials and shrubs to not cut back in fall will help keep these plants thriving for years to come. The following plants should never be pruned in autumn.

Rhododendrons and azaleas

Azaleas and rhododendrons belong to the same plant family and their pruning requirements are similar as a result. Because these plants flower on old wood, pruning azaleas and rhododendrons in fall will remove their flower buds and prevent the plants from blooming the following spring. To avoid this, only prune rhododendrons and azaleas in late spring to early summer, no more than three weeks after the plants finish blooming.

Related: The 12 Best Pruning Shears of 2023 to Keep Your Garden in Check

Lilacs

Pruning is an essential task if you keep lilac shrubs (Syringa spp.) in your garden as these plants can get unruly and grow over 30 feet tall if they are not cut back from time to time. However, like rhododendrons, lilacs only bloom on old wood and pruning plants late in the season will remove the plant’s flower buds and reduce bloom intensity. Instead of fall pruning, lilac bushes should be cut back immediately after they finish blooming in late spring to early summer.

Forsythia

Like lilacs, forsythia shrubs are fast-growing plants and they can quickly overcrowd garden beds if they aren’t pruned every year or two. However, these plants only bloom on old wood and, if you prune forsythia in autumn, you risk removing the plant’s flower buds. To avoid this, only prune forsythia bushes in spring after the flowers fade and never cut away more than a third of forsythia branches at one time.

Coneflower

Coneflower plants (Echinacea spp.) don’t necessarily need to be pruned at all, but if you like a tidier garden, it’s best to wait until spring to cut coneflowers back. If you leave this perennial's large seed heads intact in fall, they’ll provide an important food source for birds in winter and attract other wildlife to your garden as well. Beyond that, coneflower plants also readily self-sow if you don’t remove the seed heads and you’ll often get free “volunteer” coneflower plants if you wait until spring to do your pruning.

Globe Thistle

Like coneflowers, globe thistle (Echinops ritro) plants produce seed-filled flower heads. During winter, these seeds provide food for goldfinches and other birds and they help wildlife survive when other food sources are scarce. What’s more, dried globe thistle flowers remain upright throughout the winter months and they add texture to flower beds even when there’s snow on the ground.

Russian Sage

Russian sage plants (Perovskia atriplicifolia) are prized for their aromatic foliage and purple flowers, which are magnets for bees and other pollinators. However, this perennial plant can be susceptible to winter damage, especially if pruned late in the season. To ensure your Russian sage makes it through the cold winter, mulch your plants well and wait until late winter to early spring to do your pruning.

Black-eyed Susan

Black-eyed Susan (Rudbeckia spp.) is another plant that birds often forage from during the winter months, so leave the dried flowerheads in place if you can. Waiting until spring to cut back black-eyed Susan will reduce your fall gardening tasks and it will also give your flowers more time to self sow. If you want more black-eyed Susan for your garden, skip fall pruning and allow your plants to seed themselves.

Some Hydrangeas

Pruning hydrangeas can be a bit confusing because there’s a lot of variety in this plant group. Some cold hardy hydrangea varieties bloom on new wood and these hydrangea types can be successfully pruned in autumn. However, other hydrangeas, like oakleaf, bigleaf, mountain, and climbing hydrangeas, flower on old wood and these plants should only be cut back in spring or summer after the plant finishes flowering.

Related: 10 Common Hydrangea Problems, and How to Avoid Them

Mock Orange

Mock oranges (Philadelphus spp.) are famed for their highly scented flowers and they’re often grown in cottage gardens where they pair beautifully with forsythia, viburnums, and lilacs. Low maintenance and easy to care for, mock oranges don’t require a lot of fuss, but they’re another plant that shouldn’t be cut back in fall. Like some of the other plants on this list, mock oranges only flower on old wood and pruning late in the season will reduce the plant’s flower buds and diminish bloom size.

Lady's Mantle

Another cottage garden favorite, lady’s mantle (Alchemilla mollis) doesn’t really need to be pruned and some gardeners allow these plants to grow a bit wild. However, if you want to keep your garden beds looking pristine, avoid fall pruning and cut back lady’s mantle plants in spring instead. As with Russian sage, removing lady’s mantle foliage late in the season will make the plant’s roots more vulnerable to winter damage.

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