Maximizing Your Garden's Potential: 15 Essential Autumn Gardening Chores

Summer ended with a sigh of relief here on Vashon Island. Most of my perennial plants were at their wits' end after a hot and dry summer that seemed to stretch on for eons. My annual flowers, however, looked gorgeous with bright yellow and pink blossoms still busting and asking to be arranged in bouquets. As the seasonal calendar change happened on the Fall Equinox, there was an unsurprising change in weather. The air was just a little crisper, the rains finally came, and with that the grass greened up and the leaves started falling.

Now nearly three weeks into fall, I’ve been getting lots of inquiries for fall clean-up, pruning, and helping with “putting the garden to bed for the winter.” There are lots of tasks to do before real wintery weather hits, but there’s an equal amount of chores that shouldn’t be done in the autumn. You may be asking yourself “Why wouldn’t I want to do all the things before the winter hits and the weather is too horrible to work in?” The answer is simple and complex at the same time.

Perennial trees and shrubs

Wait to do certain tasks that would be detrimental and harmful to plants in the autumn. Perennial plants are gearing up for the long winter. Trees and shrubs are transporting unused nutrients from their leaves for winter storage in their roots. Once a leaf is depleted of nutrients, the plant lets go and the leaf falls to the ground. Therefore, pruning most plants now (before all the leaves have fallen) would reduce the amount of nutrients available for winter storage. This is important because those stored nutrients are used to make buds and leaves next spring. Additionally, pruning branches when it’s wet can spread diseases and further wound a plant.

For deciduous perennials (fruit trees, blueberries, maples, oaks... you get the point), wait to prune until either the winter, when the plant is completely dormant, or the early summer, when the plant can easily recover from pruning. For other plants that bloom on last year’s growth (rhododendrons, azaleas, some hydrangeas, spirea, etc.) wait until late spring or early summer after the plant has finished blooming to prune. This will allow the plant to bloom (who doesn't love flowers?) first before any drastic pruning is done.

Herbaceous perennials

On the other hand, herbaceous perennial plants (those that grow from clumps of roots, excluding tuberous roots, corms, or bulbs) such as rose campion, black-eyed Susans, echinacea, coreopsis, mints, and peonies (peonies are tuberous plants, but I'm putting them in this category because they stopped blooming many months ago) will start to turn brown and then (with more and more rain) will start to sort of “melt” into mush. When leaves are either very brown or sloppy mush, it’s safe to prune leaves and stems down to the ground. Some herbaceous perennials will have responded favorably to the lower temperatures and increased rain by putting on new, green growth at the base. In these cases, I like to prune the old leaves and stems down to the new growth and leave the new, green growth for the winter. The plant will likely stay green most of the winter and it’ll have a growing head-start in the early spring.

In much colder environments where it's either very dry or very snowy, most herbaceous perennial leaves and stems can be safely kept on the plant all winter long. When leaves, stems, and flowers (with seeds) stay in the garden and freeze, they provide forage for birds throughout the winter and don't turn into mush. In Western Washington, however, where winter temperatures are mild and rain is the dominant precipitation, most old stems and leaves will melt into mush with excessive rain. You don't have to remove the mush--leaves and stems can compost in place. However, it's my preference to remove and compost in the compost pile.

Annual flowers

As for annual flowers, many will continue growing and blooming right until the first frost (sometime in late October or November). These include zinnias, cosmos, bachelor buttons, zonal geraniums, petunias, strawflowers, and pansies. Continue to deadhead these plants throughout the fall for prolonged beautiful blooms. When the first frost hits (or if it just rains a lot), annuals will turn black or melt into mush; at this point, it’s time to thank those plants, pull them out of the garden, and toss them into the compost pile.

Other annual flower favorites like sunflowers will start to tip over and stems will break in windy, rainy fall storms. Best to remove damaged annuals when you get a chance on a clear day. Cut stems as the base of the plant (level with the soil) and toss them in the compost bin. I like to leave the roots so the soil microbes have something to eat.

Late-season perennial flowers

Late-season perennial flowers such as dahlias and begonias will also turn black at the first frost. It’s safe to either cut all the plant matter down to the ground and either leave the tuberous root/corm/bulb in the ground to over-winter or dig up and store indoors for the winter. Whether you dig or leave a tuberous root/corm/bulb is up to you and greatly depends on how much time you have (do you have the time for this chore?) and what kind of soil is present in your garden. If your garden is mostly clay and prone to pooling throughout the winter, then you should probably dig your tuberous root/corm/bulb and store indoors or risk the high likelihood that your plant will rot all winter long (and die). On the other hand, if you have well-draining soil, such as a loam or a sandy loam, then your plant will most likely be ok to overwinter in the soil.

Summer vegetables

While fall can be the most bountiful time in the vegetable garden, it’s also important to keep an eye on plants and pull when they cease to produce or when disease sets in. In my garden, this morning a few small zucchinis were harvested, but the plants themselves are in poor shape. Their broad leaves are now speckled with powdery mildew, stems have been bent and imploded from heavy rains and winds, and most fruits that have set are small and hardly growing. While it feels almost sacrilegious to pull out a plant that has the potential to produce food, do yourself a favor and reduce the spread of more powdery mildew by pulling those plants. The same goes for summer sun-loving tomatoes. Tomatoes aren’t great at coping with lots of moisture on leaves and stems and typically succumb to a variety of diseases this time of year. If you’re lucky enough to have tomatoes still on the vine, harvest all the fruit and let them ripen inside. Green tomatoes can take weeks to ripen, but also taste great in green tomato upside-down cake--yes, that’s a thing! And a delicious treat.

A note on cold-hardy vegetables and herbs

As much of the Pacific Northwest has modest winters, some vegetables and herbs can be safely planted in the late summer/early fall and grown throughout the fall and winter. These include brassicas such as chard, kale, broccoli, Brussels sprouts, and collards, in addition to some lettuce, spinach, peas, beans, radishes, turnips, leeks, onions, and carrots to name a few. Herbs include sage, rosemary, thyme, cilantro, and parsley. Throughout the fall, continue to weed around plants and fertilize when needed.

Other chores around the garden

If you have the time and a couple of good weather days, below is a list of other fall garden chores to be done before winter hits.

• Weeding beds and pathways

• Planting cover crops

• Blackberry removal

• Raking leaves

• Adding compost to garden beds

• Adding bark mulch to pathways

• Cleaning up trellising and fencing (and any other garden art, unused pots, tools, etc.)

• Putting away garden chairs and tables for winter storage

• Moving potted plants to winter homes (such as in a hoop house or protected outdoor areas under building overhangs)

• Mulching trees and shrubs (but careful not to cover stems and trunks)

• Pruning dead, damaged, and diseased branches

• Blowing off walkways, decks, patios, and driveways (over and over again!!)

• Mowing the lawn (when needed)

• Picking apples (yum!)

• Picking remaining fruits and veggies and pulling out annual plants

There are a lot of chores to do around the garden throughout autumn. The most important thing to remember is to not get carried away with pruning, as most plants shouldn’t be pruned in the autumn. However, general tidying of the garden will have it looking good and under control for most of the winter. Make sure to take special care to put away all tools, pots, artwork, and outdoor furniture. And pay special care to your soil: weeding, planting a cover crop, mulching, and composting will not only help protect soil from erosion and nutrient loss during winter rains, this will also provide needed food for soil microbes, which help build soil for endless gardening possibilities next year. Happy fall gardening!