Note: I first wrote this in midsummer and forgot to post. Apologies.
Coastal gardeners are a determined lot, particularly those who are bent on growing food. Between wind, salt and sandy soils there are challenges plenty to frustrate the best of us. But one of the biggest challenges is something we lack, namely sufficient heat from the sun.
Many of us moved here for the mild seasons. We enjoy 70ish highs in summer laden with cool breezes and late-summer fog. The persistent north winds that provide our sunny days in July and August also keep us from building up sufficient warmth for heat-loving plants.
So many of these Mediterranean-adapted plants are among our culinary favorites: tomatoes, basil, peppers, eggplant, melons, beans and cucumbers. Even more tolerant plants like beets and corn are slow to germinate or fail to thrive or ripen in the relatively cool summer days on our coast. But gardeners need not despair, it is possible to enjoy many of these tasty food plants even when you live within the "fog belt."
Certainly there are sites that simply cannot succeed in growing these plants, such as those on the "front line" of the coast: oceanfront or near-oceanfront. If you want to grow food, you would do well to consider living inland a few more blocks... or build an extremely sturdy greenhouse.
But the rest of us can achieve great results with basic building skills and inexpensive materials. Cold frames and cloches can work magic in making your crop succeed. Cloches can be as simple as heavy-gauge wire bent into hoops over raised beds, with plastic or grow-fabric attached.
Cold frames are generally more substantial, with an open-bottomed wooden frame (similar to raised beds) that supports a glazed lid. The glazing can be made from a recycled window, or new material such as fiberglass or polycarbonate. The lid can be fully removable or hinged, depending on how it will be used. We have one of each. The hinged-lid variety will be used for summer-long crops like basil and peppers that really dig the heat; the removable-lid frame is for acclimating plants as they come out of the greenhouse. The lid comes off during the day, goes on at night, until they are ready to stand the outside weather.
Finally, our vegetable garden has a large permanent cloche or mini-greenhouse for our tomato crop. The structure stands about 4' tall at the peak, and spans a 4' raised bed. It has substantial framing for year-round use, with tempered glass sides and removable polycarbonate lids for the top. In early spring and late fall we can grow greens inside, and tomatoes thrive in its shelter during summer.