With average January temperatures in the mid-60s, it's safe to say that winters in California are mild. The area has several macro-climates: interior valleys, coastal areas and mountains. The trick to a successful winter garden in Southern California, aside from knowing when to plant, is a well-prepared soil. According to the National Gardening Association, digging or tilling in compost or other organic fertilizer will take the winter vegetables through the season.
Peas are interesting plants in that they extract nitrogen from the air and store it in their roots. They are also very easy to grow, given sunshine, moist soil and something to climb on for support. Plant your peas early because if the temperature climbs above 70 degrees they may stop producing pods. The Gardening Coaches suggest harvesting your peas 3 weeks after flowering. If you wait too long they may get tough. The best time to plant peas if you live in the coastal areas of Southern California is from December to March. Interior area gardeners should hold off until January. Some varieties that you might like to try include Super Sugar Snap and Chinese Pod.
Spinach is another winter vegetable that won't tolerate temperatures much higher than 70 degrees F. Spinach is a fast-growing vegetable and is ready to harvest about a month after planting. The fun part about growing spinach is the snip-as-you-go aspect: Just snip off some leaves for your salad and the plant will grow more. When you plant spinach, throw some fish emulsion into the site. Try the Tyee, Melody Hybrid or Americana varieties. If you live along the coast, plant the spinach anytime from August to March; if you live inland, wait until November.
Radishes are the fastest-growing root crop. They also take up very little space in the garden, so you can plant them between other crops. If you plan on planting the more elongated varieties you will need to amend the soil a little deeper than for the standard radish; 6 inches deep is generally good. Radishes can be planted any time of year along the coast and from September to April if you live in the inland areas of Southern California. Cherry Bell, Easter Egg Hybrid and Icicle are some varieties that do well in Southern California.