As the days shorten and our nights begin to bring frost, many gardeners feel an urge to “tidy up” the yard before winter. Clean-up is an essential fall chore, but what it means – and how much you should actually do – has shifted in recent years. Researchers, horticulturists and conservationists are increasingly advising gardeners to balance neatness with ecological benefits.
In Colorado, where weather extremes and fragile ecosystems shape what can thrive, thoughtful fall yard work helps protect your plants, enrich your soil, and support pollinators and wildlife through the cold months.
Traditionally, garden clean-up has often meant stripping beds bare: cutting down every perennial, bagging up leaves, and hauling plant debris to the curb. While this approach delivers a tidy appearance, it removes valuable organic matter and critical winter habitat.
Instead, many experts now recommend leaving some plant material in place until spring. Seed heads feed birds, hollow stems shelter native bees, and even fallen leaves insulate plants while nurturing soil as they decompose. The challenge for Colorado gardeners is finding the right balance between aesthetics, pest prevention and ecosystem health.
Fallen leaves
Few tasks symbolize fall more than raking leaves. Across the state, aspen, cottonwood, maple and ash trees can drop thousands of leaves in a single yard.
On lawns, thick mats of leaves can smother grass and encourage snow mold, especially if they stay wet. Shred them with a mulching mower to feed the turf. Be sure to set your mower height as high as possible and make multiple passes until you can see green grass showing through the shredded leaves. Or, rake leaves off for other uses. In flower beds, a light layer acts as natural mulch, insulating roots and conserving soil moisture while decomposing into rich humus over time.
For wildlife, beneficial insects like butterflies, moths and beetles overwinter in leaf litter. Piling leaves in garden corners or under shrubs creates refuges for these species.
If you have excess leaves, consider composting them rather than sending them to landfills. Many Colorado municipalities – from Denver to Fort Collins, Grand Junction and Durango – offer seasonal leaf recycling programs. If your municipality doesn’t offer leaf recycling, check with local waste management services for options.
Perennials
In the garden bed, not all perennials need autumn haircuts. In fact, leaving many standing provides clear advantages for plant health, wildlife and garden interest. Leave standing plants like coneflowers, rudbeckia, sunflowers and ornamental grasses that hold seed heads through winter, providing food for birds like finches and chickadees. Cut back plants with diseased foliage, such as peonies with powdery mildew, to prevent reinfection.
Throw away diseased plant material; do not add it to your compost pile. Also, cut down or dead-head invasive or aggressive self-seeders to control spread. For a tidy compromise, cut stems to 12-18 inches rather than at ground level, leaving hollow stems to serve as nesting sites for solitary bees while still reducing visual clutter.
Bulbs
Colorado winters (with typical first frosts occurring mid-September in the mountains and mid-to-late October along the Front Range and Western Slope) are too harsh for tender bulbs like dahlias, gladiolus and tuberous begonias. Wait until the first light frost kills the foliage; then, on a warm day, gently lift clumps with a garden fork. After cleaning off excess soil, cure them in a cool, dry location for up to two weeks. Store in cardboard boxes with newspaper, vermiculite or sawdust in a dark spot between 45 and 50°F. A bowl of water nearby will add humidity to the dry winter air. Check monthly, discarding any bulbs showing signs of rot.
Alternatively, autumn is an ideal time to plant spring-blooming bulbs like crocus, tulips, hyacinths and many more. As a general rule, bulbs should be planted at a depth four times the height of the bulb between the soil surface and the tip of the bulb. Sprinkle some phosphorus fertilizer (0-46-0) in the bottom of the planting hole. Cover the bed with 3 inches of mulch to keep soil temperatures consistent and avoid damaging bulbs over winter.
Vegetables
In the vegetable garden, clear spent annual vegetables to prevent disease and remove pest habitat, but don’t leave beds exposed. Colorado’s thin soils are prone to erosion from wind and water run-off. Consider planting cold-hardy cover crops like winter rye or hairy vetch or spread compost and cover with weed-free straw or shredded leaves. These additions protect soil while building organic matter for spring.
Lawn care
Lawn care doesn’t end with summer. Cool-season grasses like Kentucky bluegrass benefit from autumn attention. Keep grass 2 ½-3 inches tall for your final mow; there is no reason to mow shorter in the fall. Autumn is the best time to fertilize Colorado bluegrass lawns. Apply fertilizer in October or early November (September in the mountains) for a healthier lawn going into winter that greens up earlier in spring.
Fall is also an excellent time to aerate compacted soil to improve root health and water penetration. Continue watering through dry autumn weather and on warm winter days to prevent turf injury.
Trees and shrubs
Do not prune trees and shrubs in autumn. Save major pruning for late winter. Instead, focus now on protection by wrapping young tree trunks — especially maples, lindens and honeylocust — against sunscald and frost cracks common with Colorado’s drastic winter temperature fluctuations. Water deeply before the ground freezes, which is particularly important for evergreens facing winter desiccation. Continue to water on warm days through winter when snow cover is light. Mulch around bases (not against trunks) to conserve soil warmth and moisture.
Autumn gardening isn’t just about putting the garden to bed; it’s about setting the stage for spring success. By recycling organic matter, protecting soil and roots, saving tender bulbs, and preserving habitat where possible, you’re investing in both plant health and Colorado’s environment.
So, as you pull on gloves and pick up the rake this fall, remember: a little strategic mess now can mean a thriving, vibrant garden and ecosystem next year.
Pam Rosendal is a Colorado master gardener.