GROWING GUIDE
Perennials to Cut Back After Frost
After frost, cut perennials that have collapsed into a wet mat or that are diseased. Leave seed heads, ornamental grasses, and woody herb stems that still stand. A light frost near 32°F often browns mum flowers before it kills a hardy crown. A store pot mum is not a hardy garden mum.
A cutback list is a split, not an order to mow the border. University of Minnesota Extension’s fall guidance says to leave healthy stems and seed heads of coneflowers, black-eyed Susans, and ornamental grasses for birds and overwintering insects, and its garden calendar also puts a perennial cutback in November for material that is finished. Use November for what has collapsed. Cut hosta and daylily foliage once it is a wet mat. Cut peony leaves if they are diseased, and do not compost that foliage. Leave grasses until early spring. Oregon State University’s November calendar says to cut ornamental grasses a few inches above the ground in early spring, and to trim chrysanthemums to 4 to 6 inches after they finish blooming. A light frost near 32°F browns mum flowers. Hardy garden mums, including Minnesota lines rated for zones 3–9, can keep a living crown. A florist pot mum often will not. There is no separate mum page here.
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Which perennials do I cut, and which do I leave?
Cutback list: cut collapsed or diseased foliage after frost. Leave seed heads, grasses, and woody herb stems until spring. Finished garden mums can be trimmed to 4 to 6 inches or left for insect cover. Do not expect a florist pot mum to return.
| Plant | After frost | Why |
|---|---|---|
| Hosta, daylily, other mushy leaves | Cut | A wet mat sits on the crown. Cut once it has collapsed, not on the first 32°F night if the leaves are still firm. |
| Peony foliage with spots | Cut and trash | Diseased leaves do not go in the home compost pile. |
| Coneflower, black-eyed Susan | Leave | Seed heads feed birds. Hollow stems shelter insects. Cut in spring. |
| Ornamental grasses | Leave | Oregon State cuts them a few inches above the ground in early spring, not after the first frost. |
| Lavender, rosemary, sage | Leave the woody frame | A hard fall cut into old wood is how these plants fail. A light shape can wait for spring growth. |
| Hardy garden mum | Trim to 4–6 inches after bloom, or leave until spring | Flowers brown near 32°F. Minnesota hardy mums are rated for zones 3–9. See the frost question below. |
| Florist pot mum | Do not plan on its return | A gift mum is not the hardy perennial in the Minnesota breeding notes. |
Do mums tolerate frost?
A light frost, right around 32°F (0°C), often ends the open flowers and can leave the crown of an established hardy mum alive. Minnesota’s hardy mums are selected for winter survival in zones 3–9, with frost tolerance that keeps some series blooming into October. A hard freeze blackens the display. That is not a reason to dig the crown of a hardy mum on the same day. Oregon State’s November calendar trims chrysanthemums to 4 to 6 inches after bloom. If you are leaving stems for insects, wait until spring, which is the other Minnesota cutback window. A pot mum you bought in flower for the porch is the plant people throw out after a freeze. It does not get its own URL here. Overwintering a potted mum you already own is keep potted mums over winter.
Time the job from frost dates, not from a national Monday. The rest of the year is flowers to plant each season and the autumn guides.
Common questions
Which perennials should I cut after a frost?+
Cut foliage that has collapsed into a wet mat, and cut diseased leaves such as spotted peony foliage. Hostas and daylilies usually qualify once they are mush. Do not compost diseased leaves.
Which plants should I leave standing?+
Leave coneflower and black-eyed Susan seed heads, ornamental grasses, and the woody stems of lavender, rosemary, and sage. Minnesota Extension ties standing stems to birds and overwintering insects. Cut grasses in early spring.
Do mums tolerate frost?+
A light frost near 32°F often browns the flowers and can leave a hardy garden mum’s crown alive. Minnesota’s hardy mums are selected for zones 3–9. A florist pot mum is a different plant and often does not return. Trim finished garden mums to about 4 to 6 inches if you follow Oregon State, or leave the stems until spring if you are keeping insect cover.
Is November the only cutback month?+
Minnesota’s calendar lists a perennial cutback in November and another in March and April. November is for collapsed or diseased growth. March and April are for what you left on purpose.
Sources & editorial notes
- University of Minnesota Extension: fall garden care
- University of Minnesota Extension: home garden calendar
- University of Minnesota Extension: hardy mums
- Oregon State University Extension: November garden calendar
Sources checked November 4, 2026. Compiled with AI assistance from the linked pages. This is not a Plant Care Steps growing trial. Editorial responsibility.