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.
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.
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.
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
- 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.
- 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.