Phlox
Susceptible to powdery mildew, especially in cool and wet fall months, cutting back phlox in late fall helps prevent infection. Destroy any foliage showing symptoms of powdery mildew and disinfect pruners before trimming other plants.
Bee Balm (Monarda)
Similar to phlox, bee balm is prone to powdery mildew in damp fall weather. Cutting back the plants in fall and removing debris helps prevent the disease from returning in the next season.
Yarrow (Achillea)
While some perennials retain their beauty in winter, yarrow's spent foliage can look unattractive. Cutting it back in fall, except for new basal leaves late in the season, helps protect the crown during winter.
Spike Speedwell (Veronica)
Although spike speedwell looks whimsical through spring to fall, it fades quickly after the first frost. Cutting it back to basal foliage in fall cleans up its appearance and prepares it for spring regrowth.
Astilbe
After the first frost, astilbe foliage turns yellow and brown, while the spent flowers maintain their texture. Trimming back the foliage in fall tidies up the garden while retaining the whimsical texture of the spent flowers for winter interest.
Columbine (Aquilegia)
Clearing out old foliage and flower stems in late fall sets columbine up for success in spring by preventing disease and pests from returning and removing obstacles for new growth.
Daylilies (Hemerocallis)
While not necessary for plant health, cutting back daylilies in fall provides a cleaner look through winter, avoiding mess in spring.
Hosta
Cutting back hosta foliage in fall deters slugs, which lay eggs in dead foliage, reducing their presence in spring. Leaving 4-6 inches of foliage standing protects the crown over winter.
Catmint (Nepeta)
Trimming back catmint foliage in fall removes the yellow and brown leaves after frost for a cleaner appearance, while leaving 4-6 inches standing protects the crown over winter.
Salvia
Cutting back salvia flower stalks to new basal growth in fall helps protect the crown over winter, providing a cleaner appearance in the garden.