7 Plants to Never Cut Back in September, According to Gardening Experts

A cluster of blooming hydrangea flowers surrounded by green foliage featuring various light and darker shades — Credit:
EUNBI KIM / Getty Images

Pruning is an essential task for gardeners, as it improves airflow, reduces disease risk, and encourages growth. But pruning at the wrong time of year can do more harm than good. If you're tempted to bring out your pruning shears in September, there are some plants to avoid. Certain varieties set their flower buds for the following growing season in fall, so cutting them back in September can remove next year's flowers. Other plants produce seed heads or fruit that wildlife depend on for nutrients during fall and winter, and pruning them can remove these food sources. To ensure the health of your garden and the surrounding ecosystem, these are the plants experts say to never cut back in September.

Linda Vater, plant expert for Southern Living Plant Collection
Mary Phillips, head of native plant habitat strategy and certifications at the National Wildlife Federation
Tammy Sons, founder and CEO of TN Nursery

01 of 07

Rosemary

Lightly pruning rosemary (Rosmarinus officinalis) or harvesting for culinary use in September is perfectly fine, but avoid heavily pruning this herb. "The best time for pruning Rosemary is in late spring to early summer, when it is thriving and can produce a flush of new growth," says Linda Vater, Southern Living Plant Collection.

02 of 07

Chinese Fringe Flower

Chinese fringe flower (Loropetalum) blooms in spring on old wood, meaning cutting it back in September can reduce the numbers of blooms next season. "The best time to prune is in spring after plants have finished flowering," says Vater. "Pruning in the fall can also stimulate a flush of tender, new growth that will be susceptible to cold and freeze damage."

03 of 07

American Beautyberry

American beautyberry (Callicarpa americana) produces its berries in late summer to fall, providing essential food for birds and other wildlife in late fall and winter. Cutting back the plant in September can prematurely remove its fruit supply. "The best time to prune is during dormancy, in late winter or early spring (before new growth emerges)," says Mary Phillips, head of native plant habitat strategy and certifications at the National Wildlife Federation.

04 of 07

Native Grasses

Muhly grass (Muhlenbergia Capillaris) — Credit: bauhaus1000 / GETTY IMAGES

Native grasses produce seed heads that remain on the stalk throughout winter, providing year-round interest and food for birds when other options are scarce, Phillips says. The dense clumps of foliage also provide an overwintering habitat for beneficial insects, birds, and small mammals. For these reasons, it's best to let native grasses grow freely and prune only to control their shape and size.

05 of 07

Asters

New England Aster — Credit:
Angelika Antl / GETTY IMAGES

Asters (Aster spp.) are native plants that add color and charm to gardens throughout summer and fall. Cutting these plants back in summer can remove the late-season blooms that monarchs depend on for nectar during fall migration. "Their leaf litter and hollow stems provide shelter and nesting sites for native bees and other beneficial insects that overwinter," Phillips adds.

06 of 07

Lilacs

Early Lilac — Credit:
bjdlzx / GETTY IMAGES

By September, lilacs have already set their flower buds for next spring. Pruning now means that these buds will be lost and there will be no flowers next year, says Tammy Sons, founder and CEO of TN Nursery. The best time to prune these plants is right after they flower in spring.

07 of 07

Hydrangeas

Some hydrangeas, such as bigleaf and oakleaf hydrangeas, set their flower buds during the fall and winter. "To prune them now will leave you with a naked plant next year," says Sons. Other hydrangea varieties set their flower buds on new wood and have different pruning requirements, so be sure to research your specific type before cutting.