Foggy Tourists

Poor tourists. They read about sunny California and come for their summer vacation traveling the scenic Highway 1 only to find days of fog. Fall and late spring often have much less fog than in the height of summer.

I just returned from two wonderful days on the coast 100 miles north of San Francisco. I got lucky with glorious fog-free weather. What visitors and locals fail to notice along the coastal Highway 1 is the extra 32 to 123 inches of "rain" each year. Although actual summer rain is scarce-to-nonexistent in the Northern California Mediterranean coastal zone where I live, another type of "rain," consisting of droplets of condensed fog, is a frequent occurrence. Moist summer fog condenses on the leaves of plants, mostly tall trees.

Shortly after moving to my mountain ridge, I noticed that a foggy summer evening produced the sound of steady rain beneath the tallest trees, while the meadow 20 feet away remained dry. I became obsessed with fog drip.

I put a rain gauge beneath a 125-foot tall Douglas fir tree near my garden and another 100 feet away in open grasses. The needles of the Douglas fir have an immense surface area for condensation. The Douglas fir tree averaged up to 2-1/2 times more "rain" year-round than the open field a mere 100 feet away. I discovered over 10 years of records that this single tree can gather one or more inches of water during a single heavy fog—six inches during one very foggy August! That rare six-inch fog drip equaled 163,000 gallons of water for every acre of tree foliage! It is fog drip that helps water the edges of redwood grove just around the corner from my house and allows the redwoods to expand their growth into the adjacent fields, shrubs, and smaller trees. (The trees at the edges of the forest get much more of the fog drip than those inside the grove. The perimeter trees strip most of the fog moisture from the sky.)

Fog drip is so uncommon that it is rarely found even two miles inland from my garden. I learned that microclimates can indeed be very small, special places. A microclimate that never shows up on the evening weather report. Nature sure has extraordinary niches as part of its fabric of life.

Alas, coastal-bound tourists are not impressed at all with fog drip. It rains on their parade— especially if camping in a tent beneath coastal redwoods.

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Living With the Roots of an Oak Tree

I laugh (and cry) at the little orange fences they put around oaks during construction. They are nearly worthless. While it keeps vehicles for hitting and scaring the bark, it in no way protects the feeding roots.




As a maintenance gardener I’ve had to dig up a few oaks. And just below the ground the roots have a covering much like bark. Bark absorbs very few nutrients. In a study of 25-year-old apple tree in the UK found that the first four feet from the trunk accounted for less than 10% of all the water and nutrients absorbed.

The wobbly-orange fences are, at best placed at the edge of the foliage. A good start as it may help to keep water off the trunk’s base. But this is a far cry from protecting the majority of the root system’s feeding roots.

In the photograph to the left, the construction company dutifully surrounded the oak’s dripline. But all the machinery and the house itself cover what used to be the leaf litter, duff, and organic mater (humus) that once both fed and protected the young feeding roots.

The tiny root hairs, that live for just a day or so, tend to grow up into the fertile strata of the humus and duff zone. They, like all plants, want to be the first to capture liberated nutrients as they become avaiable. As one researcher put it—“roots grow up not down”. While a bit overstated, they fact is the youngest rootlets and their root hairs reside well beyond the canopy of the tree, where all the construction is taking place. (Learn more in my book Roots Demystified,)

(See my Blog of March 31st to see diagrams of the extent of a roots wanderings.)

At one-half to thee times, or more of the width of the dripline roots gather nutrients and moisture far from the trunk or even the canopy.

The photo (on the above right) of the chairs face south along the Big Sur coastline are a good attempt to protect to crown of the young California live oak from moisture in the summer. The gravel does allow rain in the winter to percolate down along with oxygen and harmful gases escape. The compacted gravel is a bit hard on the feeding roots, but the tree seemed health. Perhaps this is one solution to living among oak woodlands.

Please post a comment - I want to know what you think.

Visit my web site to learn about my gardening books.

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NOTE: The comments section at the bottom of the post has disappeared. Click on the "___ Comments" button or the title under the "Blog Archives". Thanks, Robert