Gardening Tips for September 2026

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Things to Consider When Choosing and Planting a Tree.

• Cool-Season Annuals - The last week of September through the first two weeks in October is the optimal time to plant winter flowering annuals, such as Pansies, Iceland Poppies, and Calendula. New plantings may need protection during heatwaves. For best bloom, plan ahead so cool-season annuals are planted where they get good winter sun (preferably all day sun). Other winter annuals can be planted later in the year.
• Perennials - Frost hardy perennials, such as Lavender, Achillea (Yarrow), Columbine, Rudbeckia, Geum, Echinacea, Asters, Fuchsias.
• Trees - Bloom color can be mistakenly mislabeled. If you're looking for a specific color of Lagerstroemia indica (Crape Myrtle) buy now before blooms fade until next year. Start shopping later this month for trees that have beautiful fall color leaves.
• Winter Vegetables - Lettuce, Spinach, Swiss Chard, Broccoli, Beets, and Carrots. 
• Bulbs - Spring flowering bulbs will be arriving in local nurseries this month, shop early for best selection. Choose bulbs that are heavy for their size and free of blemishes. Here are just a few of the choices for spring bloom: Alliums, Anemone, Crocus, Daffodils, Freesia, and Sparaxis. Store in brown paper bag until planting time.
• Extras - Frost Cloth (also used as row cover to protect new veggies from insects), Dormant sprays, Mulch.

BLOG: Preparing for Winter Vegetables.

• Bulbs - Shop locally for bulbs and also online for more unusual selections (they ship when it's time to plant the bulbs in your planting zone). Mary uses Brent and Becky's Bulbs. 
• Veggies - Labor Day (first weekend in September) is a good target date to plant many of our winter veggies by seed or plant, such as Cauliflower, Swiss Chard, some Lettuce Varieties, Spinach and More. Six pack plants of winter veggies can be planted all month. Young plants may need shading on hot days.
• Pruning - Continue to prune off spent Fuchsia flowers. Clean up unwanted growth on frost hardy vines. Erigeron, Teucrium chamaedrys, Alyssum, Oregano can still be sheared if you missed doing this task in August. Frost season in Sonoma County begins at the end of October so shear plants in time for them to fill in again before frost.  
  Pest Management - Notice which frost-hardy plants have powdery mildew and spray when dormant. You can spray them now but depending on the plant the fungicide may just roll off the mildew and not get rid of the problem. Neem Oil is a preventative spray, ideally applied before signs of powdery mildew. Continue to bait for snails, slugs, earwigs and sowbugs (especially where you plan to plant new bloomers or veggies). When digging in the soil you may find immature pests that look like caterpillars (cutworms) or little, hard brown cocoon-like (pupa), discard these in hot, soapy water (chickens may like them). Check to make sure container plants that like regular water are watered well since dry rootballs stress plants and stressed plants attract pests. If ants are going in and out of a container, it’s most likely the soil is completely dry. BLOG: Watering Container Plants.
  Fertilizing - Summer annuals can continue to be fertilized once or twice a month until frost kills the plant. Roses, one last application of bloom fertilizer this month. Mary uses Maxsea fertilizers.
  Mulch - Fall is a great time to apply mulch to the garden.
  Weeding - Bermuda Grass is hitting its peak now before it starts to go dormant in winter. What an insidious weed! Herbicides only brown the top grass blades and do not kill the plant. It
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ALL PHOTOS AND CONTENT by Mary Frost (no AI).