Now that the temperatures are cooling off, or shall I say cold, it is time to put your perennials to bed for the winter. For the most part, perennials will overwinter here just fine by following these simple steps.

Cut

Once your perennials start to lose their leaves, die back and go dormant, you can go ahead and cut them back in late fall or early winter. By cutting them back to 6‐8” above ground the stem will be able to hold snow in place which helps to insulate your plants. You can also wait until spring to cut them back if you prefer, however mulch is easier to apply if they are cut back.

Mulch

Either way you’ll want to mulch your perennials with 2‐5” of mulch for the winter. The mulch can be any kind of mulching material such as hemlock mulches, pine post peelings, dried grass clippings, etc. It serves the dual purpose of keeping in winter moisture, and acting as insulation for the root system. Our perennials risk losing their root systems from tissue damage with our continuous freezing and thawing conditions. It is best to wait until the ground has frozen lightly before applying mulch, this insulation will keep the ground frozen.

Even though many plants appreciate protective winter mulch, there are some perennials that do better without additional winter mulch. These plants are intolerant of being too wet throughout the winter and risk root rot or losing their centers. On the flip side, some of our perennials are very tender and require extra winter mulch, five inches or more for adequate protection. Below are two lists of some of these perennials.

Water

Remember to provide winter water to all of your perennials during dry spells when the top portion of ground has thawed and can accept water. Water every 4‐ 6 weeks during these dry periods where there is no snow cover. Keep in mind that your perennials will wake up at different times in the spring, so don’t give up hope if you don’t see signs of life right away!

Perennials that prefer no additional mulch through winter

  • Aster     Aster spp.
  • Basket of Gold     Aurinia saxatilis
  • Black-eyed Susan     Rudbeckia fulgida
  • Blanket flower     Gaillardia aristata
  • Creeping Phlox     Phlox subulata
  • Coreopsis     Coreopsis spp.
  • Daisy, Shasta Daisy     Chrysanthemum spp.
  • Daylily     Hemerocallis spp.
  • Delphinium     Delphinium spp.
  • Dianthus (Pinks)     Dianthus spp.
  • Evening Primrose     Oenothera spp.
  • Flax     Linum spp.
  • Gas plant     Dictamnus spp.
  • Gayfeather     Liatris spicata
  • Geranium     Geranium spp.
  • Geum     Geum spp.
  • Germander     Teucrium spp.
  • Globe thistle     Echinops spp.
  • Grasses – most ornamental grasses
  • Hens & Chicks     Sempervivum spp. 
  • Iris     Iris spp.
  • Lamb’s ear     Stachys byzantina
  • Larkspur     Delphinium spp.
  • Mexican Hat     Ratibida spp.
  • Pasqueflower     Pulsatilla spp.
  • Pearly Everlasting     Anaphalis spp.
  • Penstemon     Penstemon spp.
  • Poppy     Papaver spp.
  • Purple Coneflower     Echinacea spp.
  • Pussy-toes     Antennaria spp.
  • Rockcress     Arabis spp.
  • Russian Sage     Perovskia atriplicifolia
  • Salvia     Salvia spp.
  • Silvermound     Artemisia schmidtiana
  • Soapwort     Saponaria spp.
  • Snow-in-summer     Cerastium tomentosum
  • Spiderwort     Tradescantia spp.
  • Spurge      Euphorbia spp.
  • Stonecrop     Sedum spp.
  • Sulfur flower     Eriogonium umbellatum
  • Sunrose     Helianthemum spp.
  • Tansy     Tanacetum spp.
  • Thrift, Sea pink     Armeria spp.
  • Thyme     Thymus spp.
  • Valerian     Centranthus spp.
  • Yarrow     Achillea spp.

Tender perennials that prefer extra mulch ( 5” +) throughout the winter

  • Ajuga     Ajuga repens
  • Bergenia      Bergenia cordifolia
  • Bulbs
  • Chrysanthemum     Chrysanthemum morifolium
  • English Daisy     Bellis perennis
  • False Mallow     Sidalcea spp.
  • St. John’s Wort     Hypericum patulum
  • Lavender     Lavandula spp.
  • Pincushion Flower     Scabiosa caucasica
  • Plumbago     Ceratostigma plumbaginoides
  • Wallflower     Erysimum spp.

Sources

  • Armitage’s Garden Perennial: A Color Encyclopedia. 2000. Allan M. Armitage. Timber Press.
  • A‐Z Encyclopedia of Garden Plants. 1996. Christopher Brickell and Judith D. Zuk. DK Publishing.
  • Manual of Herbaceous Ornamental Plants. 1994. Steven M. Still. Stipes Publishing.

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