Fall in the Perennial Garden: The Case for Less Clean Up

Mid Summer BorderI don’t know about you, but in my perennial garden, fall cleanup can be hit or miss. Whether a function of limited time, gardener burnout or an early cold spell, some years I just let it all freeze dry in place till the spring. What I’ve found is there are some really good reasons to do less fall clean up and I’m not as lazy as I once thought.

Here’s the case for leaving most perennial flower garden cleanup for the spring:

  • Dried foliage will help protect the crown of perennials from the freeze/thaw cycle; this is especially good for marginally hardy perennials. If  you decide to prune, leave about 3-4 inches from the ground to avoid damaging the crown.
  • Dead stems “mark” the plant and lessen the chance of accidentally digging it up or stomping on it in the spring. This can be really helpful for plants that wake up a bit later each spring (Threadleaf Coreopsis does this in my garden).
  • Plants may drop seeds and give you additional seedlings to love or give to friends next year. Such was the case with the Black Eyed Susan’s/Goldsturm Rudbeckia in the photo above.
  •  Seed heads provide tasty food for birds.
  • Enjoy the natural beauty of the winter landscape such as the ornamental grasses moving in the wind and the various colors and textures of foliage, which can be especially lovely when covered with a dusting of snow.

Bright pink Salvia Greggii /Wild Thing Sage. This semi-woody plant should be pruned in the spring. Photo courtesy of PlantSelect.org.

  • Some plants highly prefer spring pruning, such as grasses and plants with semi-woody stems such as Munstead Lavender and  Wild Thing Sage or Salvia Greggii. A spring haircut when new growth emerges often yields a plant with better form and growth. (Not to mention increased chance of winter survival).
  • Early season flowering shrubs such as lilac have already put on the growth that produce next year’s flowers. If you cut now, you will not have blooms next spring. These plants should be pruned soon
    Lilacs which were side pruned too late in the season. Photo from CSU CO Master Gardener Garden Notes #616
    Lilacs which were side pruned too late in the season. Photo from CSU CO Master Gardener Garden Notes #616

    after they are done blooming. A good general rule for lilacs is prune no later than July 4th.

Now, having said all that…here are beneficial fall care tips:

  • Cut back overly assertive perennials whose seedlings take over the garden and become a nuisance. Denver Gold Columbine and Walker’s Low Catmint are prime examples in my garden.
  • Remove leaves of plants that had powdery mildew or other foliage diseases. This will cut down the chance of the problem festering in the soil and re-emerging next spring.
  • Trim long rose canes  which can get damaged by the wind, otherwise don’t prune roses.
  •  Apply light mulch after plants have gone dormant, usually after a few hard freezes. Avoid packing mulch down too tightly so that beneficial moisture can reach the plant and the mulch does not spawn mildew or mold.
  •  Water during dry spells.  When there is little fall/winter precipitation  give the landscape a drink once a month, when temps are over 40 degrees and as early in the day as possible.

Personal preferences vary, so do what’s right for you. Just don’t beat yourself if you kick up your feet and leave most of the chores till the spring!

References for this post:

Winterizing Perennials, Plant Talk 1020

Maintaining Perennials, Plant Talk 1019

Winterizing Perennials During Drought, Plant Talk 1064

Written by Linda McDonnell, Denver County Master Gardener

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