September in the Garden

According to folklore, “cool August nights means a hot September.” If that is true, we should have a cool, pleasant month ahead, since August nights were not what I would call cool. Just the shorter days will force temperatures at least a little lower. And that means fall planting is around the corner. To me September is like April might be to people who live through blizzard-cold winters. A promise of a better season. A promise of weather changes. A promise of new beginnings in the garden. Let;s begin!

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.


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. Why not making a little space to try some unusual vegetables like Tatsoi, Chijimisai, Rapini, Romanesco Italia or Orach?  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.


Maintaining: Pay attention to anything you plant this month. In the vegetable garden, aphids and white fly may still be active, and earwigs will be emerging from summer siesta. Continue with ant baits in edible and ornamental beds. Newly transplanted trees and perennials need to be monitored for soil moisture if folklore fails and it’s another hot, dry month. If you haven’t already done so this summer, hose off shrubs and perennials. This isn’t to water the plants; it’s to rinse off the dust and disturb spider mites. Spiders, lace wings, lady bugs and praying mantis may be active, so avoid harming them with your water exuberance.

September is also clean up month. Remove tired, dying summer 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 fruit and nuts on trees or on the ground.

You can apply pre-emergent herbicide for cool-season weeds starting this month or wait until the rain will water it in for you. Watch for blue grass, brome and other non-native weedy grasses to emerge and use a hoe or hand pull to reduce their numbers.

Finished compost will look like rich soil.

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.


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. Another bit of folklore: if the bullfrog sings louder and longer than usual, rain will be coming soon. Bullfrogs are not native and are invasive in California. Maybe I will listen for the song of our native Sierran treefrog? And hope for lots of rain. I’ve built rain basins and swales to keep that moisture on my property. It’s not a pond; water from a rain basin should percolate in a week or less. The point is to have that water stay local, stored deep in the soil, instead of it running off into the storm drain or roadway.   Other conservation chores this month: Keep the bird baths full. Remove tropical non-native milkweeds and replace 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 and natural precipitation is the path to a true California garden. It’s a lot easier than fighting against weather, lack of water and wildlife. Happy September Gardening.

Narrowleaf Milkweed (Asclepias fascicularis) in full bloom: a must have for the pollinator garden…but we also like to plant other flowering natives and even annuals like zinnia to attract and provide food for adult Monarchs and other pollinators.

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