September in the Contra Costa Garden
September Garden To Dos
General Garden Care
- Adjust your irrigation. The evapotranspiration (ET) rate has plummeted in spite of hot days. Reduce your watering time by 25% from a month ago. We are headed for fall equinox.
- Pick pears, late season apples, late peaches. Irrigate if rains have not started. Pick up all fallen fruit; compost if possible.
- Fertilize citrus for the last time this year.
- Harvest tomatoes, squash, beans, eggplant, peppers.
- Start seeds of winter vegetables: bok choy, broccoli, Brussels sprouts, cabbage, Chinese cabbage, kale, cauliflower.
- Direct seed beets, carrots, chard, garlic, leeks, mache, onions, peas, radishes, spinach, sugar, snap peas.
- If you want to start lettuce seeds, remember that they germinate best in cool soil. Try mixing the seed with moist potting soil, cover and place in the refrigerator for a couple of days.
Flowers & Landscaping
- Fertilize cool season lawns: bent, bluegrass, fescue and rye. Water lawns deeply, at least once week if not raining.
- Overseed Bermuda grass lawns with perennial rye and topdress with 1” compost to keep lawns green during the winter months. Keep lawn moist until seedlings emerge
- This is a good time to shop for Lagerstroemia spp. (crepe myrtles). They are still in bloom so you can choose flower color; plant next month for best rooting.
- Fertilize roses for the last time this year. Use a liquid fertilizer and make sure it is well watered in.
- Dig up and divide overgrown Agapanthus, daylilies, primulas, Shasta daisies, Penstemon, Iberis sempervirens.
- Purchase bulbs for fall planting: Allium, Anemone coronaria, Babiana stricta, Crocus, daffodil, Freesia, Homeria, hyacinth, Ixia, Leucojum, Lycoris, Muscari, ornamental Oxalis, Ranunculus, Scilla, Sparaxis, Tritonia, tulips, species tulips such as Tulipa clusiana, Tulipa saxatilis, Watsonia.
- Look for large firm bulbs with unbroken skin. Chill tulip, crocus and hyacinths bulbs in the refrigerator vegetable bin for planting during October or November.
- Plant annuals for winter color such as Iceland poppies, violas, pansies, and ornamental kale.
- Direct seed spring-blooming plants, or plant seedlings for earlier bloom. Try Centaurea cyanus, Calendula officinalis ‘Geisha Girl’, Eschscholzia californica, Clarkia amoena, Myosotis sylvatica, Linaria marocanna, Lobelia erinus, Lathyrus odoratus, Nemophila, Schizanthus pinnatus (in warmer areas, especially West county).
- Plant perennial seedlings of Campanula, candytuft, catmint, Coreopsis, Delphinium, Dianthus, Diascia, foxglove, Gaillardia, Geum, Helleborus, Japanese anemone, Penstemon, Phlox, pincushion flower, Salvia, Scaevola, and yarrow.
- If shot hole disease was a problem on apricots during the past season, spray your trees after leaf fall but prior to rain with a Bordeaux or fixed copper fungicide. Don’t use sulfur on apricots. Visit the UC IPM page on shot hole disease for more information.
- If powdery mildew has been problem on your roses in prior months, spray now with a preventative mix: 2 tsp. baking soda + 2-4 tsp. lightweight summer oil + 1 gallon of water. Spray once a week. Visit the UC Pest Note on powdery mildew for more information.
USDA zones range from 8-9B
Sunset zones range from 7-17
Average max. temp. 82.7°F, 28.2°C
Average min. temp. 52.8°F, 11.6° C
Average rainfall .25”, .64 cm.
The fall or autumnal equinox is September 22, with equal duration of daylight and darkness.
Local Weather Information
Linked data is from the California Irrigation Management Information System (CIMIS) weather stations. Visit CIMIS web site.
Contra Costa County Stations
Month by Month Information
January in the Contra Costa Garden
February in the Contra Costa Garden
March in the Contra Costa Garden
April in the Contra Costa Garden
May in the Contra Costa Garden
June in the Contra Costa Garden
July in the Contra Costa Garden
August in the Contra Costa Garden
September in the Contra Costa Garden
October in the Contra Costa Garden
November in the Contra Costa Garden
December in the Contra Costa Garden