Fall care for perennials

October 4, 4:54 PMPittsburgh Gardening Scene ExaminerRose Field

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Black eyed Susans can provide winter interest/photo by Rose Field

Fall clean up is part of the bargain if you expect to have a lovely perennial garden, but it need not be an unwelcome chore. After weeding and doing maintenance in the heat and humidity of summer, working outside in the crisp temperatures is a nice change. Further bonuses include the knowledge that your plants will look great due to the good care and the neatnik in you (if there is one) can enjoy a tidy winter scene.

Not all perennials need fall work, and for some, spring is the best time for cutting. To balance the need for good garden hygiene with keeping winter interest, let's divide perennials and their maintenance methods into four general groups:

• Group 1: As soon as the leaves are killed by frost, or shortly before it's expected, cut the entire plant to the ground and clean up debris. If no fungus or other diseases are present, compost the cuttings. The majority of perennials are in this category, such as Phlox, Hosta, Liatris, Anemone, Veronica, Salvia, and Aquilegia.
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• Group 2: Do nothing in fall; plants should remain to provide winter interest. Most ornamental grasses fall into this category, as does Sedum “Autumn Joy”. These plants should be cut to the ground around mid-March, before new spring growth begins.
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• Group 3: Choose method 1 or 2 depending upon personal preference. Many plants such as Rudbeckia, coneflowers and Asters have seed heads which will remain over the winter on tough stems. Birds enjoy the seeds. Some folks love the winter effect of snow on the dry seed heads, some folks think it's an unsightly mess. 
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• Group 4: This evergreen group persists through the winter, some have leaves which turn red or bronze. We'll divide these into subgroups:
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  • A. Do nothing in the fall, but in spring, leaves which have become tattered can be trimmed off after the first signs of new growth appear. Bergenia, Hellebores, Heuchera, evergreen ferns and some perennial Geraniums are in this category.
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  • B. Lavender and Liriope are also in the above category, but wait a little later until spring growth is strongly underway to trim back or you'll risk killing the plant.
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  • C. Iberis is also an exception. It's an evergreen perennial that's all set to bloom in the spring. Do nothing in fall and nothing in early spring or you'll be cutting off the already present flowers. Around the beginning of June, after flowering is finished, shear the stems back by one half.

Perennials benefit from the application of a light mulch in fall. Straw or small, lightweight leaves like locust or birch leaves will work, but allowing tough, large leaves that form thick mats, such as oak or sycamore to smother plants is not good. Evergreen branches cut from a Christmas tree may be placed over perennials after the ground is frozen around New Years. Mulch helps to maintain even ground temperatures and prevent the damage done by alternate freezing and thawing.

More info:

To learn more about Hostas

To learn more about black eyed Susans

To learn more about Shasta daisy "Becky"

Follow Rose Field at Twitter: @RoseFieldWrites