Soil pH can make or break your plants' ability to absorb nutrients and thrive.
Soil pH can be tested with an over-the-counter product found at all garden supply stores. Testing the soil will tell you if your soil is neutral (7.0), alkaline (greater than 7.0) or acidic (less than 7.0).
If your soil pH is too high, limestone can be applied. If your soil pH is too low (like much of the Bay Area), sulfur can be applied. Peat moss can also help increase the acidity of your soil. Unfortunately, increasing pH takes a year or two before you will see results.
Also, it is more difficult to alter the pH of clay soils, commonly found in the Bay Area. Once you begin treating your soil, it is important to continue monitoring pH levels. In the long run, a soil pH of 6.0 - 6.5 will help your plants become healthier and more productive.
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.