Which Perennial Flowers Should Be Cut Back In Fall?

I miss the smell of burning leaves in the fall. I’m not sure exactly why we used to pile them up and burn them. I guess to get rid of them, but leaves are a great source of organic material, either composted or rototilled directly into garden and flowerbed soil. Or they can be used as protective mulch around roses and tender perennials.

It’s obvious that thick layers of tree leaves should be raked from the lawn each fall. But it’s not always obvious whether perennial flower beds should be equally tidied up in fall, or is it better to wait until spring?

Here are the time-honored rules of perennial flowerbed fall cleanup:

  • The tops of most perennials should be left intact over winter, instead of cutting them back in fall.
  • Perennial tops help the plants survive winter by catching and holding a deeper snow layer, which is a good insulator.
  • When they’re left intact, the tops add interest to winter landscapes and provide shelter and food for birds.
  • Tops should be left on ornamental grasses during winter, and then cut cleanly above ground level in spring before new grass spears emerge.
  • There are exceptions, however. Some perennials should have their tops cut down to a few inches above ground level in the fall after we’ve had a frost or two. This includes peonies and any perennials whose foliage was diseased from powdery mildew or other blights. (Throw diseased tops in the trash.) Likewise cut back perennials whose foliage becomes very limp after frost, like iris, hosta and daylilies. If left until spring, the foliage is so mushy that cleanup is difficult, and the limp foliage does little to catch snow or aid in winter survival.
  • Although it’s tempting to rake and clean the perennial bed in fall to make it look nice, fallen leaves and stems provide insulation against damaging freezing/thawing cycles.
  • Tender roses and perennials that are borderline in winter hardiness benefit from 12 to 24 inches of leaves mounded over the plants in late October before severely cold weather arrives.
  • Next spring, (usually during April) cut back perennial tops after winter’s coldest temperatures have likely past, and before new growth emerges from ground level. Remove protective mounds of leaves, which can be spread around the perennial bed for weed control and moisture retention, or they can be dug into the soil to improve its tilth.

Happy Gardening! 

8 Responses

    1. Don Kinzler

      Hi Bev. If you scroll down the comments, I replied about phlox, but let me know if you’re not seeing it, or it’s not appearing for you. Hopefully you got a notice that I replied. Thanks.

    1. Don Kinzler

      Rhubarb can be susceptible to leaf diseases, plus it turns to mush over winter, so it’s best to clean it up in the fall after a few frosts. Then carefully pull or cut off the stems. Leaf-disease organisms overwinter on the old material, so it should be removed from the garden and disposed of. Thanks.

    1. Don Kinzler

      Hi. It depends on the type of hydrangea. The large-flowered white Annabelle types that die back to ground level each year are best cut back in spring. The dried flowers are often decorative over winter. Then cut back to about 6 inches above ground level in early spring, before the new growth begins at the base. The paniculata hydrangeas, that have pyramidal-shaped flower clusters, (like Vanilla Strawberry), grow like other shrubs, and don’t die back. So the only pruning they need is to remove the dry, dead, flower clusters in early spring.

    1. Don Kinzler

      Hi. The tops of tall, garden phlox are best left intact over winter, and then cut back in spring. The tops are fairly substantial and strong, so help catch snow during winter. The low-growing creeping phlox can be trimmed back. Thanks. I should mention, though, that some tall phlox varieties are very susceptible to blights and mildews that turn the foliage from green to yellow to brown during the growing season. If the foliage of phlox was diseased, then it’s best to follow the rule of cutting back diseased plants in the fall and disposing in the trash.

Comments are closed.