It’s true. Gardeners can be obsessively tidy — and proud of it. But, as research on wildlife habitat, biological pest control and soil fertility shows, a certain amount of untidiness is actually beneficial to garden health.
When fall frosts and winter’s chill zap your garden, by all means remove the wilted annuals from your pots and beds. But resist the urge to cut perennial wildflowers and grasses back to the ground. Go lightly on pruning woody shrubs and trees. Leave some dead stalks untrimmed. And don’t rake up the leafy detritus that accumulates under shrubs to leave “clean” beds.
Your garden will thank you with enriched soil, enhanced growth and increased biodiversity, from birds and butterflies to the kinds of microbes that act as the soil’s immune system, employing antibiotics to control outbreaks of harmful rusts and other pathogens. Many plants also possess a sparse sort of architectural beauty when stripped to their essential forms, with their stems bleached, bark peeling or chunky seed heads shimmering in the low light of winter.
Susan J Tweit
1. Go easy with those pruning shears. It’s common practice to prune shrubs and trees for shape and to open their canopy in the fall. Check for food sources like berries, other fruits and seeds of all sorts before you prune. The china-white berries on redtwig dogwood (Cornus sericea) and the brilliant red berries on winterberry (Ilex verticillata), for instance, are easy to see and avoid pruning out, as are the plump hips on wild and hybrid roses. These fruits are valuable for migrating and wintering birds, providing them with much-needed energy and sources of vitamins and antioxidants to keep them healthy.
Many other woody plants provide fall and winter food for birds and other small wildlife. The chaffy seeds crowning the rubber rabbitbrush (Ericameria nauseosa) in this photo may not look desirable, but come late winter when pickings are slim, small songbirds like bushtits swarm these shrubs for just those seeds.
Let your woody plants look a little less tidy in winter so that their berries, other fruits and seeds are available to feed wildlife in the hungry months.
Susan J Tweit
2. Leave some dead stalks untrimmed. The hollow centers of dead plant stalks, whether annual sunflowers (Helianthus annuus) with their pithy middles or the hollow culms of ornamental bunchgrasses such as basin wildrye (Leymus cinereus), form natural nesting habitat or “dens” for overwintering eggs and larvae of many beneficial insects.
Solitary nesting bees and predatory wasps, for instance, will lay their eggs in the hollows of constructed nest blocks like the one in this photo — which includes bamboo, native grass and sunflower stalks, along with drilled wood dowels. Insects preferentially choose to use standing dead stems over nest blocks, in part because the natural stems aren’t so crowded, resulting in less competition for both space and for the emerging larvae.
Solitary nesting bees are not only important pollinators of many garden plants, but they also provide critical food for nesting songbirds in summer. Healthy populations of these insects form part of your garden’s natural bird food. Predatory wasps prey on many detrimental garden insects, keeping their populations in check.
Susan J Tweit
3. Mind that trimmer. It’s so tempting to cut down perennials once frost nips them and kills their leaves. But leaving at least some of these stems and leaves standing adds beauty, food and shelter to the garden.
The rusty-red clumps of little bluestem (Schizachyrium scoparium) in this photo are good candidates to feature over the winter. Their rich color contrasts beautifully with white snow, the tall stalks give height to winter-flattened garden beds, and the feathery seeds provide food for songbirds and other small wildlife.
Standing bunches of grass and other tall vegetation also act as snow fences, catching snow and other moisture, and casting shade that allows the snow to melt slowly and sink into the soil for spring moisture. There is a downside to this: Don’t leave tall vegetation standing where it will collect snowdrifts on sidewalks, patios or driveways.
Susan J Tweit
4. Avoid the “buzz cut” look. Know your plants and their growing habits so that when you do cut them back, you don’t whack off their growing tips. The growing tips of perennial grasses and flowers aren’t all at ground level. Some, such as big sacaton (Sporobolus wrightii) and basin wildrye, grow from nodes as high as 6 inches above the soil. Cutting back too far will keep them from resprouting and may injure new growth sheltered in the dead leaves of the clump, as is shown with the green and pinkish blue grama (Bouteloua gracilis) leaves in this photo.
Basal clumps of leaves and stems also provide shelter and cover for overwintering insects and other beneficial garden inhabitants, which leads to the next bit of advice.
Susan J Tweit
5. Create microclimates of thermal cover. The salmon-pink flower spike in this photo beautifully illustrates the idea of thermal cover: This threadleaf giant hyssop (Agastache rupestris) bloomed until mid-November in a USDA Zone 5 garden at 7,000 feet in elevation in the Colorado Rockies, protected both by the thermal mass of the ceramic pot behind it and the wind shelter of an untrimmed clump of little bluestem grass. Those two kinds of thermal cover — the dense pot able to soak up and retain solar heat, and the wind-resistant clump of bunchgrass — kept the normally frost-tender giant hyssop protected and blooming until nighttime temperatures dropped into the single digits, far below the normal frost-kill range for this Southwestern native.
Boulders, garden structures, walls and even large pots can provide the thermal mass to create sheltered microclimates in the garden. Tall masses of plants break the wind, providing thermal cover of their own. This circles back to the first lesson: When pruning, remember that dense shrubs and trees provide thermal cover for overwintering birds and other wildlife, so go easy with those shears,
Susan J Tweit
6. Put down that rake. “Clean” flower beds, with the soil raked bare, are not necessarily healthy beds. Leaving organic litter in place helps mulch and feed the soil, shading that underground ecosystem to keep it cooler on hot summer days and warmer in winter. Organic litter also retains moisture and decomposes to release nutrients that help plants grow. And dead leaves hide the cocoons of butterflies and other pollinators.
Observing where birds hang out in the winter garden demonstrates the benefits of untidy beds. The leaf detritus under the bed of old floribunda roses and other “heritage” shrubs and perennials — those with historical horticultural significance — in this photo attracted a canyon towhee in a sleet storm to scratch busily in the leaf litter, searching for insect larvae and other arthropods to eat. A flock of noisy juncos hung out in the shrubs above the towhee, picking hips from the roses and seeds from the catmint plants. Nearby beds that had been raked and trimmed to tidy bare soil were silent, attracting no birds.
Susan J Tweit
7. Practice conscious untidiness. Recognizing that tidiness is a deeply held garden aesthetic, be judicious about where and how you practice untidiness. Public areas of the garden, including the front yard or beds adjacent to sidewalks and driveways, are examples of where tidiness may be more important for aesthetic reasons.
It may also be important to tidy up where enthusiastic plant growth impedes walkways or drives, as in this photo, where a native plant meadow featuring billowing clouds of Indian ricegrass (Achnatherum hymenoides), the curling bunches of blue grama and native wildflowers including sky-blue Lewis flax (Linum lewisii) spills over onto the public sidewalk. Cutting back the plants along the front margin of this meadow gives a tidier appearance and aids in snow removal, but leaves the rest of the meadow intact.
The bottom line: Practicing judicious untidiness promotes biodiversity, improves soil and plant health, and provides habitat for pollinators and songbirds.
Get a Head Start on Planning Your Garden, Even if It’s Snowing
What to do in your garden this month