I’m thinking of “resilience” as we enter September and a new season. After years of drought, this year has brought historic flooding to end winter and enter spring, heat waves but also periods of unseasonably cool summer weather, thunderstorms and wind, a tornado or two, and measurable, in some cases significant, rain in August. What will Autumn bring? Unlike us, our plants cannot go to the coast to beat the heat, evacuate when wildfire threatens, or go indoors and shut the wind and rain out. They must develop resilience against whatever comes—weather, insect pests, disease, and mechanical damage, including intentional, such as when prune and trim. September begins the busiest season for gardeners in our central valley and foothill areas. As we are planning renovations, designing new gardens, and doing annual cleaning, let’s celebrate the plants that have demonstrated resilience to all life throws at them and practice conservation and other measures to increase resilience in the whole garden.
Planting: Fall is the best season to plant almost everything in your ornamental garden. In our area we start our fall planting a week or so before the autumnal equinox on the 22nd. Trees, shrubs, perennials, and ground covers all establish and grow best when planted in the fall rather than the spring. Do as much new planting as you can beginning this month and continuing until early December. The exceptions are avocados, citrus, cactus, and other frost-tender plants unless you are prepared to protect them all winter and early spring.
In the edible garden, September is a good month to plant the seedlings of broccoli, cabbage, and cauliflower that you began last month. You can also start some more seedlings for succession planting. You can direct seed carrot, lettuce, parsley, green onions, peas, radish, chard and other greens, turnips, seed potatoes and flowers like calendula, alyssum, snapdragon and poppies. It’s a busy month, with removing the last of the heat loving plants, cleaning up the garden, adding compost, and replanting with cool season crops. Make sure you monitor irrigation for your new seedlings as we may still have plenty of warm days and no rain.
Maintaining: Pay attention to all new transplants, ornamental or edible. In the vegetable garden, aphids and white fly may still be active, and earwigs will be emerging from summer siesta. Continue with ant baits. Newly transplanted trees and perennials need to be monitored for soil moisture.
September is a good clean up month especially if you don’t trim and prune year round. Remove tired, dying summer edible garden plants. Don’t add any plants to the compost bin that have diseases or pests unless your compost will heat up to at least 165 degrees Fahrenheit. Trim and prune shrubs, evergreen trees, and perennials except late summer/fall bloomers. Trim and divide bulbs, corms and tubers if you haven’t yet. They need to be replanted by Thanksgiving. Dispose of any remaining overripe or shriveled fruit and nuts on trees or on the ground.
You can apply pre-emergent herbicide for cool-season weeds starting this month. Did anyone brilliantly apply it right before the August storm? Remember: pre-emergent herbicide must be watered in well to activate it. Watch for blue grass, brome and other non-native weedy grasses to emerge and use a hoe or hand pull to reduce their numbers.
Compost can be top-dressed in all beds. Compost is not fertilizer, but it will help keep the soil healthy and encourage organisms living in the soil that plants need.
Check soil moisture with a monitor or your hand to adjust watering as the weather changes. Heat waves may occur, so be ready to pre-irrigate as needed to keep plants stress-free. Wind is desiccating too, so pre-irrigate if windy days are forecast.
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, butterflies and moths are still active and all of them have a place in the well-managed garden. Many of our butterflies and moths are late this year so hold off trimming milkweed and other flowering plants until at least the end of the month. Consider building rain basins and swales to keep rain on your property. Water from a rain basin should percolate in a week or less. If you connect your storm gutters to the rain basin, consider where the overflow will run and make sure it’s not to your door! The point is to have as much water as possible percolate and be stored deep in the soil but in a small yard you may still need to make use of municipal storm water drain systems (aka gutters).
Other conservation chores this month: Keep the bird baths full. Remove tropical non-native milkweeds (orange/yellow flowers) and replace them with a native California species. Consider replacing a few more high-water-use ornamental plants with those that thrive on less water. Planting species that are adapted to our climate is the path to a truly resilient California garden. It’s a lot easier than fighting against weather, water unpredictability, and wildlife. Happy September Gardening!