Fall is a time when many people are outside, “cleaning up” their yard in preparation for anticipated harsh weather ahead. It’s also the perfect time to plant trees, shrubs, perennials, garlic and ornamental bulbs.
When you’re not admiring the gorgeous colors and scents of autumn, get out the rake* and clean up, but do it very carefully. Don’t be too tidy or you will remove cover for many beneficial insects. Many people seem almost phobic about leaves on their yard’s soil, even though it’s Nature’s way of protecting and enriching the soil. Fortunately, obsessively neat traditional gardeners -- who wouldn’t think of leaving herbaceous plantings standing through the winter -- are being replaced with gardeners interested in the wildlife value of their garden. They see the beauty in allowing Nature to do its thing and in seed heads that are not only invaluable for birds and insects, but also bridge the gap between autumn color and the first crocus.
What I like to do is rake* the leaves from any lawn and paved areas, directly onto beds and borders, anywhere there is bare soil. I pull any weeds and then toss leaves between plants, keeping them off plants’ crowns to prevent rotting. Perennials, particularly those that grow naturally under trees, thrive with leaf mulch which protects their roots from frosts. This organic matter is later returned to the soil by worms drawing it in and microbes breaking it down, so leave as many leaves in situ as possible. Winter will continue the process as deciduous plants collapse. (Late next spring, rake up whatever is left that you don’t like the looks of and add it to your compost pile. At that time you can mulch beds again with homemade compost or the certified organic leaf compost available at the City of Portland’s Sutherland Yard just off NE Columbia Blvd. It’s rich, reasonably priced and eliminates the plastic bags that come with buying bagged compost. For more info call 503-823-4990.)
While many gardeners claim that raking leaves from beds controls slugs and other pests, removing leaves actually may increase the numbers of these pests by reducing the hiding places of predatory beetles that prey on them. These beetles need cover to survive and mulch protects them from other predators and cold temperatures. In our garden we never kill anything and we have very few pests; I’m convinced it’s at least partly due to leaf cover (and the occasional visiting opossum who likes to dine on snails and slugs!). Also consider leaving some rotting logs, branches and stones around the garden to help provide winter cover for our beneficial friends.
According to Seattle Tilth’s “Maritime Northwest Garden Guide,” tree leaves are “the best concentrators of calcium, magnesium and trace minerals on the terrestrial world. These minerals are very important to seedling growth, and by composting the leaves, these nutrients are made easily available to young plants. All leaves are not created equal; common leaves in order of best mineral content are: oak, beech, maple, ash and elder.” So gather as many as you can and compost away! (Note: Walnut and horse chestnut tree leaves have chemicals that can inhibit growth, so don’t use those).
Leaving winter “skeletons” will also provide food sources for birds, in addition to homes for dormant insects. Although many perennials collapse into a soggy mess in the fall, many do not and the seed heads of many perennials, such as coneflowers and bee balm, provide food. Try this: leave your plantings once they have died back. Then on a sunny winter day, take a peak: your first impression may be that of messy dead foliage, but look closely and you will see intricately designed seed pods, cones and capsules. When things really start to look ratty, cut back as needed, but let the strongest stand into late winter.
There are, as you might expect, exceptions to this. Many tropical plants that we grow for vegetables (tomatoes, peppers, eggplant, cucumbers, etc.) are susceptible to a number of diseases, so remove those decaying plants when they die back to decrease the chances for pathogen buildup in your vegetable beds. Rotating crops is also a good idea. Mulching overwintering veggie crops, such as kale, with leaf mulch is fine.
If you grow vegetables, October is the perfect time to increase soil fertility organically. Sow cover crops now – clovers, peas, vetches, beans and others -- that grow in a symbiotic relationship with soil-dwelling bacteria, and nitrogen will be available next spring when the crop is turned under (they can also be chopped up and composted). This so-called “fixing” of nitrogen lets you add less nitrogen fertilizer the coming year. Cover crops also protect the soil from excessive winter rains.
In addition to nitrogen, all plants, especially edibles, need adequate supplies of phosphorous, potassium, and micro nutrients such as sulfur and calcium, and fall is the optimal time to test the soil for these essential nutrients. A soil test will provide information on how to adjust the soil content. To obtain a soil test, visit A&L Western Agriculture Lab’s website.
With the exception of tender plants, fall is the best time to plant nearly everything: bulbs, trees, shrubs and perennials can all go into the warm, moist soil before winter. If you work fast, you can still plant seeds in the kitchen garden such as fava beans, delightful in the spring tossed with garlic and olive oil. Garlic, shallots and others in the onion family may also be planted now. For garlic especially, be sure to loosen and amend the soil with plenty of compost and fertilize with a good balanced organic fertilizer at planting time and again at the beginning and middle of spring (see my article on growing garlic). Ornamental bulbs can also be dug up, divided and replanted, to increase stock and improve flowering. ). In general, plant flowering bulbs at a depth of two to three times the height of the bulb in well drained soil.
As winter approaches, we come to a turning point in the garden. Cold snaps wilt frost-tender plants and we once again see birds like juncos coming down from the mountains for the winter. While it seems like all growth has stopped, amazing things are happening below the soil’s surface and roots are developing to prepare for next year’s growth. The soil is still warm enough for planting almost anything, from berry bushes to trees. Fall may be the end of a cycle, but it is also a wonderful climax to a year of growth.
* Considering using a leaf blower rather than an old-fashioned rake? Don’t! Leaf blowers are not only loudly obnoxious; they waste fuel, heavily pollute carcinogens and CO2, and threaten public health and quality of life. Much more on this in a future blog …