How to Winterize Perennial Flower Beds

Some plants can be left untrimmed, adding unexpected beauty to your snowy landscape. (Cy86/Shutterstock)

Every flower gardener knows that pruning is part science, part art. The goal is breathtaking flower displays balanced by robust plant health. Fall is one of the most important seasons when it comes to giving plants a good trim, and many seasoned gardeners know the secret trick to having the best spring and summer blooms on the block.

There’s a temptation to cut everything down to the ground, which makes the garden look clean and crisp, but there are many reasons not to do so, starting with local wildlife, such as finches, sparrows, jays, chickadees, and more, which will dine on the dried seeds when food is otherwise scarce. While dried stalks and seedpods aren’t attractive when bare, they add depth, dimension, and a soft beauty to the landscape once the first snow begins to fall.

Many perennials benefit from being cut back to the ground. (Andrii Salomatin/Shutterstock)

The Don’t List

For those in cold regions, not trimming a plant back also helps to protect the plant’s crown, the area where the stem connects to the roots, found at the soil line, from which new growth will appear in the spring. The following plants will benefit from this added protection: coneflowers, black-eyed Susans, milkweed, red hot pokers, geraniums, stonecrop (sedum), false indigo, and ornamental grasses and ferns.

As a bonus, ornamental grasses look simply delightful when covered in snow and dancing in a gentle breeze. Some gardeners say that bee balm and phlox should be trimmed back as well to prevent powdery mildew, while others leave them untouched for the birds.

Snip, Snip

What plants do need hard pruning? Plants that don’t benefit wildlife or add to the snowy landscape don’t need their crowns protected. Most of these plants actually benefit from being cut back to the ground, as it reduces the chance of disease and leaves the crown clean for spring growth. These include irises, daylilies, peonies, Shasta daisies, garden yarrow, lungwort, spike speedwell, astilbe, columbines, salvias, catmint, and—not a flower, but probably planted right next to them—hostas.

Damaged or diseased plants should also be cut back, and the cuttings tossed out, not used as mulch, which could potentially spread the disease.

Bulb Behavior

Dahlias, gladiolus, cannas, and other tender bulbs and tubers should be dug up at the end of the season. Be sure to wait until the plant begins to die back or after it’s killed by the first frost. Be sure to loosen the soil carefully around the entire plant and lift the bulbs gently, being sure not to cut them in the process or damage their fragile skin, as this can lead to disease and rot. Rinse off any soil with a garden hose, and allow the bulbs to dry and cure by placing them in a well-ventilated area out of direct sunlight that has temperatures of 60 to 70 degrees. Once cured, pack them in sawdust, vermiculite, or lightly moistened sphagnum peat.

Note: Too much moisture can lead to rot. Some gardeners dust the bulbs with fungicide before packing them. Storage container options range from cardboard boxes to plastic bins, plastic or paper bags, or pretty much whatever’s at hand.

Weeds, Leaves, and Annuals

Take advantage of the cooler weather and lack of (most) bugs to give the garden bed a thorough cleaning. Garden litter is more than unsightly; it’s a potential haven for pests and diseases. Remove, then trash or burn weeds, as many of their seeds can overwinter in a compost pile. Weeds are some of the hardiest plants in the garden, so this is an opportunity to break their lifecycle. Likewise, tree and shrub leaves that fell into the perennial beds should be removed. They can be either discarded or composted to recycle their nutrients. Otherwise, they can promote snow mold and encourage rodent activity.

Annuals need to be removed, too. Some can be saved for next season by digging up the entire plant before the first frost and moving it into a pot to enjoy the winter inside. Some can be saved by taking and rooting cuttings. A few plants, such as the colorful and versatile coleus, which, while grown for their eye-catching leaves, actually do get delicate flowers, can be grown using either method. If you’re going to toss a plant, inspect it for diseases before adding it to the compost pile.

Organic Winter Blanket

After the flowerbed is thoroughly cleaned, it’s time to add some mulch. In addition to preventing moisture loss, it also regulates soil temperature. This is particularly important in areas that experience repeated freezing and thawing, as it reduces temperature fluctuations and gives tender plants a better chance at winter survival. It also adds organic matter to the soil as it breaks down over the winter and will help nourish the plants as they begin to pop up in spring.

Dahlias and other tender bulbs and tubers should be dug up when the plant begins to die back or after it is killed by the first frost. (ABO PHOTOGRAPHY/Shutterstock)

Perennial Hydration

While flowers aren’t typically fertilized in the fall or when they’re dormant, good watering habits are still essential.

Fall Moisture

Even when plants aren’t actively growing, they should be watered regularly up until the first frost. This will be a lot less frequent than they need during the summer. Only water when the soil is dry, as tested by a moisture meter or finger inserted into the soil to the first knuckle.

Winter Wet Down

Perennials should be watered during prolonged droughts, but only when the temperature is above 40 degrees F and there’s no snow cover. Water at midday so that it has time to soak in before a potential evening freeze.

Spring Soak

Begin a regular watering schedule as soon as the flowers begin to show signs of growth, at a rate of one inch per week. Water deeply and less frequently to encourage deep roots. Keep in mind that drought-tolerant perennials are only able to handle drought stress once they become established.