Garden Mastery Tips
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October 2001 |
Rethinking Fall Cleanup and Mulch, Mulch More…
Fall Cleanup
Are you cutting back perennials in the fall for no other reason than your intolerance of "nature's untidiness"? If so, author Piet Oudolf would have you revise your ways. Remove stems that have become messy or really unattractive; compost or shred them to be recycled in the garden. Let the rest of the stems remain, for a number of good reasons. Dead stems may provide:
- late fall and winter interest in the landscape, especially when covered with snow or frost
- some frost protection for ground-level buds or overwintering mounds of leaves
- seedheads and insect life to feed the birds
Plants which Oudolf recommends letting stand through winter include Achillea, Agastache, Amsonia, Astilbe, Cimicifuga simplex and cultivars, Echinacea, Eryngium, Eupatorium purpureum 'Atropurpureum', Monarda, Nepeta species, Phlomis species, Rodgersia, Rudbeckia, Sedum cultivars, and the grasses Achnatherum brachytricha and Deschampsia cespitosa.
Oudolf claims that these plants "die well": Aster, Aconitum, Anemone japonica hybrids, Cimicifuga simplex, Helenium autumnale hybrids, Kirengeshoma palmata, Persicaria amplexicaulis, Rudbeckia, Scutellaria incana, Sedum telephium cultivars, Solidago cultivars, Trycirtis formosana, Verbesina alternifolia, and the grasses Miscanthus and Molinia cultivars.
As you incorporate grasses into your landscape, look for those which have good color and shape in autumn and winter. See Ornamental Grasses for Southwestern Washington.
Perennial Care
Do trim and dispose of any disease- or pest-ridden perennial stems. As you evaluate your borders, make sure that the position of each perennial (or group of the same variety of perennials) is marked in some way. The variety name should also be on a label in the border and/or in a planting diagram in a gardening notebook or file.
During the fall, as perennial foliage begins to die, divide perennials which are:
- flowering less profusely each year
- growing beyond the space allotted to them and encroaching upon neighboring plants
- developing bare or dead centers
Marginally hardy, recently planted or shallow-rooted perennials benefit from a light cover of a non-matting material such as the lightest of evergreen boughs, weed-free straw or stemmy hay, or pine needles. Caution! Straw and hay, especially if applied quite thick and before the weather is really cold, attract rodents looking for winter warmth. Pine needle mulch should be reserved for plants which thrive in acidic soil. Waiting until at least late November or early December to apply mulch gives the plants a chance to gradually get used to the cold; during that period, one would hope that the resident rodents would settle somewhere outside the perennial bed, as well. Sawdust, shavings and most leaves settle and pack too much to be of real value as mulch.
Do You Do Dew Point?
Some weather forecasters give the dew point (the temperature at which moisture in the air condenses and dew forms). When dew forms, the heat released helps keep the air temperature at or slightly below the dew point. More moisture in the air at sunset means that frost during the night is less likely. Frost is also less likely when there is good cloud cover or wind. Clouds help keep the heat stored during the day from escaping the zone where plants are growing; wind mixes up cold and warmer layers of air. There is a high probability of frost overnight when temperatures are below 50 degrees F at sunset, the sky is clear, and there is no wind.
Moisture in the top foot of soil around your plants offers frost protection. Moist soil holds more of the sun's heat than dry soil, and heat is released when water evaporates, keeping air temperature near the ground higher. Since it takes time for moist soil to store heat, don't wait to water until just before frost is predicted. In spite of its many benefits, mulch prevents soil heat from rising to warm the air around plants.
Love Me Tender…
When the first frosts of fall are predicted, cover tender plants with old sheets or blankets, newspapers or paper bags, pine branches, straw, inverted flower pots, or water-filled cloches. Opaque materials offer better protection than clear ones. Plastic does not hold heat well. Covers applied early in the evening retain more heat. Covers held off plant leaves with stakes provide better protection than those merely laid over the plant. Before serious winter weather, move valued container plants to a protected frost-free area or bury them in sawdust or ground bark to keep the roots from freezing.
Fuchsias
The Tryphylla fuchsia hybrids, which includes the fairly common Gaartenmeister, should be kept at or above 45 degrees F during the entire winter. Allow other container fuchsias to harden in a protected outdoor location until late November: refrain from dead-heading, fertilizing, pinching, pruning or repotting them. Water them less frequently, but don't let them dry out completely. Before placing fuchsias in winter storage in a cool (35-40 degrees F) dark place with good air circulation, remove any remaining leaves. Avoid hard pruning, which may leave a moist place where fungus could take hold. If you are short on storage space and must prune, allow some drying time before the plant goes into storage. During the winter, give a minimal amount of water to the plant(s) once a month or so.
We haven't asked, but we suspect that Piet Oudolf has no fuchsias in hanging baskets. He probably doesn't even have hardy fuchsias growing in his borders. Had we asked, he'd likely be asking us to rethink this whole fuchsia thing, too…but he doesn't live in the Pacific Northwest, and we do…
Sources
- Harper, Pamela, and Frederick McGourty. Perennials. Los Angeles, California: HP Books, 1982.
- Jesiolowski, Jill. Learn to Predict Your Own Weather. Organic Gardening, December 1993, pages 24–30.
- Oudolf, Piet and Noel Kingsbury. Designing with Plants. Portland, Oregon: Timber Press, 1999.
- Tozer, Eliot. An Eye to the Sky. Horticulture, March 1998, pages 59–64.
- Tozer, Eliot. Predicting the First Frost. Organic Gardening, September/October 1999, pages 54–56.
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