What should gardeners be doing (or not doing) this fall to help plants survive the winter and thrive next spring? How does one protect bird nesting and pollinator habitat or get a jump-start on next season’s pest control? Here is a detailed to-do list to help you “put the garden to bed.”
Our average first frost in the Portland metro area usually arrives in mid or late November.
- There’s still time to plant spring-flowering bulbs, garlic, and cover crops!
- Scatter slug bait in perennial beds and vegetable garden areas every three weeks during mild, wet weather (Monterey’s Sluggo and Bonide’s Slug Magic are both wildlife- and pet-safe).
- Continue planting/transplanting trees, shrubs, and perennials until the end of the month
- Divide summer-flowering perennials, hosta, daylilies, ornamental grasses, etc.
Leave the Leaves
Wildlife experts and conservation groups are urging us to not rake up or remove our fallen leaves these days. In many cases, this is great advice and will benefit lots of bees, butterflies, and other pollinators and beneficial insects, as well as the birds that depend on them for food.
- In shrub beds and landscapes areas, rake leaves into beds and underneath shrubs as mulch; allow to break down over time (takes about 6–9 months for most leaves to decompose).
- Rake up and collect or compost leaves to use later as mulch, once broken down.
- Do not leave a thick blanket of leaves on top of turf grass or lawn areas; only a fine layer of chopped or shredded leaves should cover grass to avoid damage.
- Large leaves can be mowed or shredded to make smaller; avoid doing this unless absolutely necessary—shredding can damage insect larvae and changes natural texture and composition.
- If you can’t see your plants underneath the leaves, it is probably wise to pull them back; avoid piling wet leaves around winter pansies to reduce fungal issues.
- Some plants have extremely waxy or slow-to-decompose leaves (e.g. Evergreen Magnolia, English Laurel, Rhododendron); if possible, it’s best to keep these leaves underneath the plant they fell from—let them break down slowly in place.
Cut Back & Prune
Cut back: Hybrid tea/floribunda roses to chest or waist-high to minimize winter wind damage; secure climbing rose canes to support structure
Prune now: Only as needed—damaged tree limbs or those that may cause damage in wind or ice storms; provide stakes to newly planted trees in high-wind areas (remove after first year)
Do not prune: Rhododendron/Azaleas, spring-blooming trees, or shrubs—pruning now may remove next season’s flower buds and cause plant to not bloom; these plants are best pruned after they flower in spring
Prune in early to mid February: Japanese Maples, blueberries, most fruit trees; cut back old foliage on Hellebores, Epimediums, and Sword Ferns just before new growth or flowers emerge
Prune in mid-February: Most hybrid tea and floribunda roses, summer-flowering Clematis, winter-dormant ornamental grasses (if not cut back in fall), and hardy Fuchsia (cut back to new growth as spring leaf buds begin to swell)
Mulch & Protect
Get ready to mulch and protect tender plants and garden beds. Use compost, straw, wood chips, or fallen leaves to cover soil 3–4 inches deep. Mulch helps protect soil from compaction, suppresses weed growth, reduces soil moisture evaporation, and can add slow-release nutrients as the material decomposes.
- Since mulch insulates soil, it is best to wait until we have had one or two killing frosts before mulching (Thanksgiving is a great time to mulch and work off some extra calories).
- Keep mulch away from tree and shrub trunks by leaving a 4 to 6-inch area clear at the base.
- Avoid smothering evergreen perennials; keep mulch 4–6 inches away from most plants (okay to cover a dormant plant as long as it is uncovered in spring).
- Tuck a little slug bait underneath mulch in perennial and edible beds.
Tropical & Indoor Plants
Tropical and indoor plants should already have been moved to protected locations for winter. If you intend to keep a citrus plant outside, move it to a sheltered area (near house, under eaves/cover) and place stakes or unused tomato cage in the pot to help support frost cloth, or cover during low temperatures (wrap with incandescent holiday lights for extra warmth). Only water when soil looks dry, maybe once per month.
Dahlias
Dig them if you do; cover and mulch them if you don’t! A little slug bait under winter mulch is a great idea. After the plants begin to die back from frost, cut the stalk back to about 1–2 inches and cover it with an upturned, empty can (tuna fish or cat food cans are perfect), weigh the can down with a rock, and cover area with mulch at least 4 inches thick. Have extra blankets, sheets, or frost cloth ready and accessible for extra winter protection, as needed. Be sure to remove mulch and empty cans in spring as growth resumes, and add more slug bait as tender shoots appear.
Dormant Spray
Many plants that struggled with pests or diseases this year can be treated with a dormant spray while they are leaf-less to improve their health next spring. Fruit trees, Dogwoods, Lilacs, Roses, and many other edible or ornamental plants can be sprayed with a copper spray (diseases) or an oil spray (insects). Spray applications should be done two or three times while plant is dormant—Thanksgiving, New Years, and Valentine’s or Presidents’ Day are ideal application target dates.
Other Fall Gardening Tasks
- Drain above-ground irrigation lines and blow out or winterize irrigation systems.
- Pull hoses into garden shed or garage for storage.
- Collect, clean, sharpen, and oil tools before storing for winter.