August in Southern California represents a unique transitional period for gardeners. Though the weather remains intensely hot, this month marks the final opportunity to complete the summer growing season while preparing for the mild winter harvest. Successful gardening depends on balancing the immediate challenge of high temperatures with the need to establish plants that will thrive in the coming cooler months. This requires strategic planting choices to maximize remaining warmth and careful heat management for young cool-season crops.
Extending the Summer Harvest
The prolonged heat allows for one last push of warm-weather vegetables, specifically fast-maturing varieties. Planting bush beans in early August is a good strategy, as they produce a yield more quickly than pole beans, reaching harvest before the first significant cooling trend. Quick-growing zucchini varieties can also be planted now, capitalizing on high soil temperatures to rapidly establish and produce fruit.
Heat-loving greens, such as Malabar spinach or New Zealand spinach, thrive when traditional lettuce struggles. These alternatives maintain a fresh green harvest. Small pepper varieties, like jalapeños or shishitos, can be planted from existing transplants for a late-season yield. Selecting quick-to-mature options ensures a final bounty before warm-season crop productivity naturally decreases.
Starting the Cool-Season Crops
August is the definitive window for initiating the cool-season garden, requiring seeds to be started indoors or in protected areas to shield them from the current heat. Starting these plants in August gives them the necessary time to mature before the winter holidays.
- Brassicas, including broccoli, cauliflower, and cabbage, should be sown now to develop robust seedlings ready for transplanting in late September or October.
- Leafy greens, such as kale, collards, and Swiss chard, also need an August start, often benefiting from the relative shade of a covered patio or indoor grow light setup.
These young plants will be less prone to bolting once established. Root vegetables, including carrots, beets, and radishes, should be direct-sown into the garden soil, as they do not transplant well. Their germination window aligns with the moderating late-August soil temperatures.
Heat-Tolerant Herbs and Ornamentals
Many culinary herbs from the Mediterranean climate are well-suited to the dry heat of Southern California and can be planted in August. Perennial herbs like rosemary, thyme, and oregano thrive with minimal fuss. They establish themselves well in the warm soil and will provide continuous harvests.
Basil, which is sensitive to cold, should be planted from transplants now to ensure a final flush of leaves before cooler nights slow its growth. For decorative appeal, annual flowers such as zinnias and marigolds flourish in the intense sun and provide continuous color into the fall. These ornamentals can be planted from seed or transplant for an immediate impact.
Techniques for Surviving the August Heat
The primary challenge in August is managing intense solar radiation and high ambient temperatures, requiring specific watering and soil management techniques. Watering should be deep and infrequent to encourage the development of deep root systems that access cooler, consistent moisture. Watering early in the morning minimizes evaporation loss and allows plants to absorb water before the peak heat arrives.
Newly planted seeds and young transplants, especially the cool-season starts, benefit significantly from the use of shade cloth, which filters out the harshest afternoon sun. A 40% to 50% shade cloth is ideal for vegetables, reducing heat stress without limiting the light needed for photosynthesis. Amending the soil with a layer of organic mulch, such as straw or compost, helps regulate the soil temperature and locks in moisture, reducing the need for constant surface watering.