September Gardening Guide for the South Bay
How to Make the Most of Late Summer and Early Fall in Your Garden
September is a transition month in Southern California gardens. The blazing days of August start to mellow, but the soil is still warm, the light is long, and conditions are perfect for both harvesting and planting. For South Bay and Greater Los Angeles gardeners, this is one of the most rewarding times of the year: you can prepare for a robust fall and winter garden while still enjoying the tail end of summer blooms and harvests.
Food Gardens: What to Plant Now
Cool-Season Crops (Time to Sow!)
September is prime time to plant cool-weather veggies that will thrive as temperatures continue to drop:
Leafy Greens: Lettuce, spinach, kale, Swiss chard, and arugula love the cooler nights. Sow seeds directly or set out seedlings.
Brassicas: Broccoli, cauliflower, Brussels sprouts, and cabbage can all be started now. These take longer to mature, so planting early in fall ensures success.
Root Vegetables: Beets, radishes, carrots, and turnips can be sown directly into the ground or raised beds. They do best in loose, well-drained soil.
Herbs: Cilantro, parsley, dill, and chives enjoy cooler weather.
Warm-Season Holdouts (Don’t Pull Yet!)
Tomatoes, peppers, and eggplants will often continue producing into October if you keep them watered and pruned. Pinch off flowers late in the month if fruit isn’t likely to mature before the first cool spell—this redirects energy into ripening existing fruit.
Basil can still be productive but will bolt as nights cool. Consider harvesting heavily and making pesto to freeze.
Ornamental Gardens: Color for Fall
Fall-Friendly Planting Ideas
California Natives: September is a good time to start planning and prepping soil for native perennials like California poppies, ceanothus, and sage. They establish best when planted in fall as seasonal rains (hopefully) begin.
Chrysanthemums and Marigolds: Both thrive in fall and add cheerful color to borders and containers.
Ornamental Grasses: Fountain grass, muhly grass, and blue fescue provide movement and drama in autumn gardens.
Succulent Refresh: Cooler temps reduce stress on succulents—making it a great month to propagate, repot, or design new succulent arrangements.
Lawn & Landscape Care
September is one of the best months to dethatch, aerate, and overseed lawns in the South Bay. Warm soil encourages germination, and fall rains help establishment.
Reduce irrigation frequency slightly as days shorten, but don’t cut back too much—new plantings need consistent moisture.
Garden Tasks & To-Dos
Soil Building: Add compost or aged manure to beds before planting fall crops. Healthy soil = healthier plants.
Mulch: Refresh mulch around ornamentals and edibles to retain moisture and regulate soil temperature.
Pest Check: Whiteflies, aphids, and spider mites can still be active. Use a strong stream of water to knock them off, or introduce beneficial insects like ladybugs.
Deadheading: Remove spent blooms from roses, zinnias, and dahlias to encourage a final flush of flowers.
Seed Saving: Collect seeds from summer annuals like sunflowers and zinnias for next year. Store in paper envelopes in a cool, dry place.
Useful Tips & Tricks
Stagger Your Planting: Plant leafy greens every two weeks to ensure a continuous harvest throughout fall.
Carrot Hack: Cover newly sown carrot rows with a lightweight board for a few days to keep soil moist and cool for germination. Remove once seedlings sprout.
Companion Planting: Plant radishes around brassicas—radishes grow fast and help distract pests like cabbage loopers from your main crops.
Pollinator Power: Add fall-blooming flowers like cosmos and alyssum near your vegetable beds to attract beneficial insects.
Citrus Care: If you have backyard citrus (common in South Bay gardens), give trees a final feeding of citrus fertilizer this month before cooler weather sets in.