How will your garden grow (underneath winter’s snow)?
If you’ve been procrastinating about preparing your garden for winter—and next spring—don’t despair! You still have time.
Sarah Tietbohl and Sarah Dickert, Smithsonian Gardens horticulturists, answer these questions and give invaluable advice for gardening enthusiasts about gardening in the colder months.
How should we prepare our gardens for the fall and winter? Should we rake leaves or place them in flower beds and lawns until spring?
Be lazy! Only do the bare minimum! Unless leaves are more than an inch or two thick in garden beds, there is no need to remove them. Leaves provide sources of winter shelter and nesting material for many insects and critters that are important parts of a healthy garden and ecosystem. The same goes for cutting down perennials and ornamental grasses. Not only do seed heads provide visual winter interest in a garden, but birds will eat the seeds and hollowed stems are another source of shelter for insects, such as solitary bees. And as the leaves decay, they return nutrients to the soil, helping the garden to be happier and healthier the next year.
If leaves are not too thick on lawns, they can simply be mowed over (i.e., chopped up) and allowed to compost in place as nutrients for the lawn. Or even bag them while mowing to spread as mulch in your garden (again, no more than an inch or two thick). Try using a mulching blade on your mower to chop the leaves more finely. However, a heavy leaf layer on grass will kill it, so it’s ideal to chop the leaves as much as possible or remove them. They make excellent “brown material” for a compost pile!
What’s the optimal time to plant bulbs for spring blooms? Will any bloom in winter?
Spring-blooming bulbs can be planted any time October/November through January, if the ground is not frozen. There are not any bulbs that truly bloom in January or February, but some bulbs bloom sooner than traditional daffodils and tulips—such as winter aconite (Eranthis), crocus, Adonis, and snowdrops (Galanthus). Depending on your region, you may see some bulbs, like Galanthus and Adonis, blooming in February if you have warmer winters.
Are there plants that will add interest and survive through the winter—anything aside from plants such as ornamental cabbage?
Any kind of evergreen tree or shrub will always provide a sense of green during the dreary winter months. Even some evergreens, such as camellias, will bloom in the winter (check out our collection in the Enid A. Haupt Garden!). Or plants like hollies will have bright red or yellow berries. And don’t underestimate the beauty in bark. Trees like coral bark maple, crape myrtles, and birches or shrubs like red and yellow-twig dogwoods all have wonderful bark. Some witchhazels will start blooming in February, always a welcome sign that spring is around the corner! Perennials can still add interest too—don’t cut off seed heads or cut down ornamental grasses in the fall. At Smithsonian Gardens we plant annuals such as pansies, wall flowers, ornamental cabbages and kales, parsley, mustard greens, bok choys, and Carex to provide pops of color throughout the winter months and in anticipation of warmer spring days. (Also see Alex Dencker’s sidebar below.)
Any suggestions for maintaining a vegetable garden in the cold months?
There are several cold-tolerant veggies that can be planted in the fall for a quick turnaround of late season harvesting and even some that may hold over until the spring. Think cabbage, kale, salad greens, radishes, peas, onions, beets, carrots, turnips, and garlic. More tender cold-tolerant plants (e.g., salad greens) will appreciate being protected from winter weather if they are covered by frost cloth. Use the chopped-up leaves from your lawn as a mulch layer to suppress winter weeds, help keep winter veggies insulated, and return nutrients to your garden soil. Or instead of planting veggies, you can plant cover crops like clover or winter rye that will be tilled back into the soil in the spring, providing nitrogen. In general, winter is a great time to rebuild the nutrients in your soil, whether by using cover crops or some type of compost.
Are there plants particularly suited for container gardening? Anything to keep in mind when planting in a container for cold weather? Can vegetables be grown in containers?
Any of the cold-tolerant annuals listed above work wonderfully in containers. Use a statement plant like red-twig dogwood or a small evergreen as the focal point of the container, then fill the outer edges with annuals. But just remember that even though its cold, the container may still need some water. Plants can dry out quickly in wind and cold temps, so the roots will be looking to take up some water on warmer days. Veggies like dinosaur kale and parsley are both ornamental and practical for winter container gardening.
What are some good plants that can provide winter food or habitat for birds and other wildlife?
Look for plants that provide seeds, berries, or nuts as food sources, or fiber they can use for nests. Top plant choices include coneflowers, hollies, milkweed, Virginia creeper, black-eyed Susans, elderberry, dogwoods, oak trees, and ornamental grasses. Just remember to select the native varieties of these plants since birds and wildlife have evolved to eat and gain the best nutrition from them.
How should you overwinter tender plants and bulbs (e.g., elephant’s ear, lilies, caladiums, etc.)?
If these plants are planted directly in the garden and you want them to go dormant over the winter (vs. trying to keep it living as a house plant), gently dig them up, carefully remove the bulk of the soil, place them in a container, and put them in a cool, dry, dark area for the winter (garage, basement, closet, etc.). Treat plants already in containers the same as garden plants. Do not water the container over the winter so the roots don’t rot. Some plants like dahlias can be dug from the garden, remove all the soil from the tubers, and store nestled in a dry material (such as shredded newspaper or wood shavings) in a paper bag. Then around April and May, bring the containers out from hiding, water them, and place them in a sunny location to start bringing them back to life before putting them outside for the summer.
What if you have terrible soil? When is the best time to amend it and with what?
That depends on your definition of “terrible” soil—clay, sandy, wet, dry, sunny, shady? In general, the best remedy for poor soil is usually the addition of organic material, though this will not fix all problems. As mentioned in the first question, start by allowing plant debris to decay naturally in your garden. Take a cue from nature, nothing is out there raking up leaves in the woods or cutting back perennials in a prairie! You can also add a layer of compost in the spring, no more than an inch thick, but do not till/dig it in. That will damage plant roots and overly disrupt the natural soil composition. The other solution is to work with the “terrible” soil, not fight against it. Research plants that grow naturally in your soil type instead of forcing plants to live in soil they are not well adapted for. Check out the presentation “Learning from Nature: The Importance of Field Botany” from our Let’s Talk Gardens webinar series to learn more about that process.
Any additional tips or thoughts about cold-weather gardening?
Try not to think that the garden is boring in winter! Include plants that will attract wildlife that is fun to watch or ones that have textures and colors that wouldn’t necessarily be appreciated during the summer when flowers compete for attention. Learn to enjoy your garden in all seasons!
There are many fall-blooming native perennials including coneflowers, black-eyed Susan (my favorite), the very tall ironweed, the “pollinator magnet” goldenrod, and the best fall flowering perennial – asters. The aromatic aster (Symphyotrichum oblongifolium) has bursts of blooms as the chilly fall weather arrives, offering its flowers as a needed source of nectar for many insects as they get ready for winter.
Asters – Both annual and perennial asters are prized for their ability to attract fall pollinators. While annual varieties typically produce larger, showier flowers, perennial species often produce stunning mass plantings. Asters provide a profusion of small flowers which open on long branches and range in color from white to deep purple. Like many native plants, perennial asters are exceptionally robust and resistant to disease and insect damage.
Solidago (Goldenrod) – Yet another native plant for fall pollinators, goldenrod is most commonly found growing in the borders of meadows and along roadsides. Though some may not consider this plant to have great ornamental use, it is of great value to late-season pollinators (and not the cause of fall allergies!).
Helianthus (Sunflowers) – Open-pollinated and heirloom varieties of sunflower are a great asset to fall flower gardens. In addition to their beauty, sunflowers sown in succession can yield valuable nectar for insects up until the arrival of the first frost. Easily grown from seed, these adaptable annuals also produce highly nutritious seeds for birds and other small backyard wildlife.
Two very simple things you can do this fall: plant native perennials, shrubs, and trees, and leave the leaves. These measures will provide habitat in the form of winter cover from fallen leaves and food for pollinators and birds from native flowers. If it is out of habit or guilt to stay busy and you need something to do then take the dog for a walk or tidy up the garage, just don’t rake the leaves!
Alex Dencker, Horticulturist
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Posted: 25 October 2022
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Categories:
Collaboration , Education, Access & Outreach , Feature Stories , Science and Nature
