Indicating Past Fires

I’m chopping firewood and remembering all the old native Pacific madron trees (Arbutus menziesii) that used to grace pockets of the forest around my house. The trees rarely occur in pure stands. Some had trunks three feet or more in diameter at breast height (DBH). (I don't know who's breast.) Over the past 22 years all but a handful have died a natural death and were resurrected as firewood.

At only 80-100 years, these are so short-lived trees compared to the mixed coastal oak (Quercus agrifolia), Douglas-fir (Pseudotsuga menziesii), tanoak (Lithocarpus densiflorus), the California coast redwood (Sequoia semperviren) – with a DBH of 8-25 feet - and California bay trees (Umbellularia californica) in “my” forest. This is because the madrone, while drought resistant, is a colonizer of fire-scorched earth. They are among some of the first trees to sprout after a fire. It is said the seeds need fire to germinate. (However, most germination in nurseries is done by freezing the seed before planting in flats or tree tubes.) These trees at first grow more rapidly than the Douglas fir trees associated with a more mature forest. They help to stabilize the soil. Eventually the Douglas fir trees grow above the madrones and shade them to death.

To maintain madrone in a mixed Douglas fir, oak, and redwood forest, the tree needs fire. Not a firestorm in the tops of mature trees, but frequent fires about every five to 50 years. Pacific madrone depends, on these periodic fires to eliminate or greatly reduce the beginning of a Douglas fir overstory.

However, the forest here hasn’t burned in over 100 years. (A 1/2-acre fire last week a mere two miles from my house was quickly extinguished. What a close call and a relief!) The amount of “kindling” (dead trees and shrubs as well as the invasion of foreigners along parts of the forest’s edge like Scotch broom (Cytisus scoparius), which act like little balls of standing gasoline because they burn so easily and hot) on the ground is tremendous. When the next fire comes the burning grasses or Scotch broom will leap up the trunks of the trees to form a crown, or canopy, firestorm. Nothing, except the noble redwoods, will be left. Including my house.

This photo is of one of the few Pacific madrone trees left on the property as it snakes toward sunlight from beneath the maturing Douglas fir trees.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Splitting in the Wind

The Douglas Fir tree in the left photo didn’t commit suicide. It was just “squeezed" off by the other poorly attached branches. This phenomena is called included bark – and occurs on defective V-shaped crotches in which the bark grows inward and on itself, causing a physical weakness when the co-dominant leaders meet. [Two vertical trunks about the same height.]

Notice the fallen branch was sharing the same area of the trunk with three other branches. This tree was topped during a wind storm some 40 to 60 years ago. The loss of the single leader [tallest, vertical shoot] caused four side limbs to compete to become the new leader. In the process, the interior tissue had to share increasingly smaller amounts of tissue. This lead to a structural weakness that allowed a slight wind to cause one of the limbs to jetison. The close up shows the darkened wood where the attachment was very weak.

The photo on the right is a Liquidambar tree [also known as a Sweet Gum tree in the Midwest] that exhibits the same problem – included bark. As mentioned above this happens when two shoots share the same location of growth. The trick to preventing this, as cabling is not an option, is to buy trees without two trunks attached at the same point. Or, prune off one of the leaders when the tree is young.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Dripping My Way Through the Forest

For anyone interested in water, a rain-gauge is not only an essential tool and toy, but a great topic for cocktail party chit-chat. Did you know, for example, that one can actually overlook 30 to 60 inches of "rain"?

I live on a high ridge dividing a hotter, dryer inland plain from the more temperate, wetter Pacific Ocean climate some five miles to the west. The non-drought average rainfall on top of my cloud-scraping ridge is about 60 inches per year.

Shortly after moving here, I noticed that a foggy summer evening produced the sound of steady rain beneath the tallest trees—even though a meadow 20 feet away remained bone-dry. I soon learned that in my Mediterranean coastal zone, summer "rain," consisting of droplets of condensed fog, is a frequent occurrence

In this climate, with its summer fogs and winter rains, moist air condenses on the leaves of plants and forms droplets like the hot-weather "sweat" on a bottle of cold soda. The collective needles of the Douglas fir trees near my house offer an immense surface area for this condensation.

I set up a rain-gauge beneath the tallest (125 -foot) Douglas fir tree, and over six years I've discovered that this single tree gathers one or more inches of "rain" each summer night during heavy fogs, and half-again to twice the year-round "rain" of the adjacent open meadow. The month of August usually produces six inches of summer fog drip, or an amazing 163,000 gallons per acre of tree foliage!

To utilize nature's original "drip irrigation" and take direct advantage of this free rain, I plant beneath the dripline of the Douglas firs near my patio The difficulty is finding plants that are somewhat drought-tolerant, shade-loving and deer-resistant. So far my list includes most of the varieties of Daphne (Daphne spp.); wild ginger (Asarum caudatum); native Western ferns; foxgloves (Digitalis spp.); huckleberry (Vaccinium ovatum); Forget-me-nots (Myosotis scorpioides); salal from Northern CA, OR and WA (Gaultheria shallon); the native thimbleberry (Rubus parviflorus); Euryops pectinatus (gets leggy, must have late evening light); and various ornamental grasses. Soon to be infiltrated by Rhododendrons spp., Azaleas spp., and bear berries (Mahonia spp.)

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

Visit my web site to learn about my gardening books.

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