September is the month we begin to remember that the winter solstice is approaching. Days grow shorter steadily, until by month's end we have only 12 hours of daylight to work with. Compare that to July's 15 hours. That means cooler temperatures and even chilly mornings. We've had a few of those in August, and most of us gardeners have rejoiced and gotten to work. So, more of that in September, as we start on larger outdoor projects.
Planting: Our Tulare and Kings counties Master Gardener chapter has an excellent user-friendly guide for vegetable planting developed by two of our UCCE Agricultural Advisors, Michelle Le Strange and Manuel Jimenez, "Vegetable Planting Guide" : https://ucanr.edu/sites/UC_Master_Gardeners/Local_Gardening_Articles_-_Info/Vegetable_Gardening/ (Or go to our Home Page, https://ucanr.edu/sites/UC_Master_Gardeners/ and enter "Vegetable Planting Guide" in the search bar).
I've been using it since I first moved to the foothills of central California, even before I became a Master Gardener. This month, the guide instructs us to plant the following from seed: Asian greens, beets, carrots, cilantro, lettuce, green onions, radish, rutabaga, spinach and turnips. Transplant seedlings into the garden for broccoli and cauliflower. If you didn't get your seeds started in August, go ahead and plant from seed early in the month for all these cruciferous vegetables, including kale and cabbage. But don't wait too long: these cool season veggies like to germinate in the warm soils, then mature in the cooler air and soils of fall, but they can start to go dormant and toughen up if they get too cold. We don't mind a bit of frost on our collard greens, but the leaves should be ready to pick when that frost comes. So choose a lovely September day and get the cool-season garden filled up! But what to do with those heat-lovers still taking up space? You can try companion or biointensive growing, which is another way to say, "crowd it all in," but with a method. Or you can say goodbye to summer and start removing plants. The first ones to go should be plants that are attracting pest insects. Challenging day at work? Go yank out some old tomato vines or bedraggled squash plants and take a deep breath.
You can also begin to plant perennials and shrubs, especially towards the end of the month when the daytime temperatures should be in the 80's and the nights in the 50's. You still must have your irrigation system up and running because we won't reliably get our seasonal precipitation for another month. So early in the month is the time to do renovation or installation of an improved, more efficient watering system. Costs have come down on smart controllers; maybe this is the year to upgrade?
Don't plant citrus or bougainvillea or other species that can suffer frost damage. Wait until spring for those.
Maintaining: This is a busy month in the garden. I think it's one of the best months to do a semi-annual clean up, especially in the native and no-lawn gardens that are becoming so popular. Prune, trim, hedge, chip or haul out…and get that garden looking fresher and ready for winter. All your spring-blooming shrubs like our native sage, penstemon, bush anemone, and our non-native shrubs like lilacs should be pruned early in the month if you haven't already done it. Don't wait too long or you won't get any flowers next year.
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This is also the month to dig out and divide over-crowded perennials and bulbs. How about a plant-sharing party with your gardening friends? Extra bulbs can be cleaned up and stored in a cool dark place for planting in cooler fall.
Deep water trees and shrubs through the month. Hose off cobwebs once or twice this month to discourage mites. September is also a good month to apply pre-emergent herbicide to prevent annual bluegrass and other winter weeds from taking over the garden. You must water a pre-emergent in, so be prepared to saturate the garden or wait another month and apply right before a rain event. Or perhaps it will rain this month? Although as of now, the weather forecast is calling for "abundant sunshine" all month.
If you still have a cool-season lawn, this is the month to apply fertilizer. Follow the package directions of a fertilizer meant for lawns and err on the side of too little instead of too much. You can also give your roses a treatment of ¼ cup each of Epsom salts Ironite per bush. Apply to the soil around each plant.
Conserving: While you're trimming and slashing your way through the garden, keep an eye out for wildlife you want to conserve. Lizards, spiders, toads and moths are still active and all of them have a place in the well-managed garden. Continue with ant baits to reduce these enemies of beneficials without using highly toxic broad-spectrum insecticides. Keep the bird baths full. Trim flowers off tropical non-native milkweeds. Those are the ones with yellow/orange flowers. Experts tell us this helps prevent monarchs from staying in our valley too long into winter and then not being able to migrate before the cold kills them. This year, perhaps more native milkweed (Asclepias) will be available in local nurseries and plant events? Look for names like "narrow-leaf milkweed" and "showy milkweed," and don't be afraid to ask if it's locally native. If you plant this fall, expect it to take a year or two for the Monarchs to find your plants: be patient.
Being patient is a lesson from gardening we can use in all parts of our lives. Good things take a little time. The careful work we do in September will give us satisfaction immediately but will really pay off next year with healthy plants, abundant flowers and a mini nature preserve outside our doorstep.