September Garden Almanac
September marks the beginning of fall – and the beginning of the fall planting season. The next two months is our “Second Spring” in the Sonoma Valley. You can start cool-weather crops in the vegetable garden – many of which you can harvest all the way through next spring.
September is also a great month to get new shrubs and trees planted. The soil is still warm and roots can get started now and accelerate their growth in the spring, native trees and shrubs included. Trees and shrubs started now will be well prepared for a hot summer next year.
Here is a garden and nature roundup for September:
Annuals: Time to start thinking about fall and holiday color: plant calendula, pansies, Iceland poppies, primrose and snapdragons. Sow sweet pea seeds in the garden this month for late winter and early spring bloom. Replenish mulch and spread compost this month.
Perennials: Fall and spring are the best times of the year to plant perennials in the Sonoma Valley. Perennials planted now will have the benefit of another month or so of warm soil; they will be well prepared for growth next spring. Group perennials by sun and water needs.
Bulbs: Prepare bulb beds for planting this month and next. Spring-blooming bulbs planted in the next month include daffodils, Dutch iris, muscari, and ranunculus. The rhizomes of Bearded Iris can be set out this month. Plant winter cyclamen now for blooms in November and December.
Roses: Withholding fertilizer and decreasing watering will encourage roses to go dormant by mid-winter. To extend the bloom season continue to feed roses for another month. Check roses for insects – aphids on new growth and spider mites under leaves. Spray aphids with a strong stream of water; use a miticide against spider mites.
Shrubs: Plant shrubs in autumn. Wet planting holes before setting plants in, then be sure to keep the soil just moist as roots get established. Decrease automatic irrigation to established plants as the weather begins to cool. Add aged compost to planting beds.
Trees: Plant trees in autumn; choose fall bloomers now while they are in color. Feed evergreens in the fall, but not deciduous trees. Add plenty of aged compost around the dripline of established trees. Winter rains will take nutrients deep to the roots.
Vegetables and Herbs: Set out cool-season starts now: Brussels sprouts, cauliflower, cabbage, celery, lettuce and parsley. Potatoes and onions can be set out now. Turn aged compost about 6 inches deep into idle planting beds. Sidedress new transplants with aged compost.
Fruits and Berries: Place a 2-inch layer of compost around fruit trees and berries – to retain winter moisture and moderate cold. Clear the garden of dropped fruit and debris which can harbor pest insects.
Garden Maintenance: Start a compost pile this month: alternate layers of garden and vegetable refuse, soil, and manure. Start with a 6-inch layer of prunings and straw, add a 4-inch layer of cow manure, then a 4-inch layer of leaves, vegetable tops – and continue alternating layers until you have a 3 or 4 foot pile.
Native Plants: Natives in bloom this month include woolly blue curls, California poppies penstemons, clarkias, asters, and evening primrose. This is a good time of year to start cuttings of native shrubs including Carpenteria, Ceanothus, and Ribes – red flowering currant.
Nature Alerts: Perching songbirds – passerines – are migrating south this month. Look for warblers, flycatchers, gnatcatchers, thrushes, vireos, and orioles. More than 430 species of birds have been identified on Point Reyes. Look out for poison oak this month – vines of bright red leaves climbing trees and thickets – “leaves of three, let it be.”
Kenwood Weather Averages: Temperature: Average High 83°F, Average Low 52°F, Mean 68°F; Average Precipitation 0.35 inches; Record High 110°F (1971), Record Low 34°F (1950).
Sunrise and Sunset: Sunrise on the 1st 6:40 a.m. Sunset on the 1st 7:41 p.m. Sunrise on the 30th 7:06 a.m. Sunset on the 30th 6:55 p.m.
Moon: Last quarter/waning on Sept. 5; New on Sept. 13; First quarter/waxing on Sept. 21. Full on Sept. 28.
– Compiled by Steve Albert
Steve Albert is the author of The Kitchen Garden Grower’s Guide available at Amazon.com. He teaches in the landscape design program at the U.C. Berkeley Extension. He lives in Oakmont.