Heat waves around here usually follow a predictable pattern. When a zone of high pressure camps out over our part of the state, the first few days are typically windless or there can even be a slight off-shore breeze (from the land toward the ocean, instead of the opposite which is our usual state of affairs). What this means is that temperatures here at our farm can be nearly equal to the inland areas where daytime highs in the 90’s and above are the summertime norm. By the third day we start looking to the West for relief, and it seldom lets us down. Sometimes it simply takes the form of a breeze, cooled by its passage over the California Current. Other times it takes the much more dramatic form of an advancing wall of fog—like the seagulls arriving en mass to save the Mormons from their plague of locusts. When this happens, temperature can drop 10-20 degrees in short order—welcome relief indeed for both people and plants.
As with any weather aberration, the effects of a heatwave on a small, diverse farm like ours are mixed—some things really like the additional heat, others not so much. The crops on the “summery” end of the spectrum like squash and basil seem to double in size in just a few days while the “cool season” crops just look stressed. Hot, dry weather can also favor certain crops pests, like cabbage aphids in brassicas and two-spotted mites in strawberries. Extreme heat can burn the exposed strawberry fruit as well, and at times like these it is helpful to have big healthy plants to provide cover.
The main challenge during heatwaves is to keep everything hydrated—both crops and people. Fortunately, the new well that we had installed several years back has performed flawlessly, and provides us with plenty of water to stay on top of our increased irrigation tasks. The heavy clay soils that we farm on are also a real blessing at times like these because of their ability to retain moisture. And the use of cover crops and compost to keep the soil organic matter levels high adds even more of a buffer.
The one place where no such buffer exists is in the greenhouse where we grow our transplants and it is here that we typically suffer the most damage. Because the transplants are grown in shallow trays that dry out quickly, and the light intensity is much higher inside, and we have to water several times a day just to keep the plants cool.
Yesterday we were treated to the remnants of a “Southerly Surge”, a mix of fog and breeze that typically starts along the immediate coast down around Point Conception and works its way North. By this afternoon and tomorrow the more typical onshore pattern is expected to re-establish itself meaning we should be back in the 60’s and 70’s by the weekend.
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