Tuesday, October 23, 2012

Tallest Trees on Earth

I don’t have a bucket list, but if I did, a visit to the Redwoods National and State Parks would be at the top of the list. Have you visited?

On the way to an American Conifer Society Western Region conference in Petaluma, Calif., Kym Pokorny, garden writer for The Oregonian, and I drove the 31-mile long Avenue of the Giants. This route in southern Humboldt County makes accessible the largest remaining stand of coast redwoods. Fog drip is critical to the moisture-loving redwoods, but the day we visited it was a clear, warm, mid-October day with few other visitors to intrude upon the quiet forest.

Redwoods are very special trees. While they once had a substantial range, they now are only found from the southwest corner of coastal Oregon to the coast line of Monterey County in California. They can create their own fog through transpiration and are more successful reproducing by sprouting from the base of mature trees—or cloning—than from seed (seed viability is less than 20%). Thick, tannin-rich bark, combined with foliage starting high above the ground provides good protection from fire and insect damage, contributing to the coast redwood's longevity. The oldest known specimen is about 2,200 years old; many others exceed 600 years. The largest coast redwood is the "Lost Monarch"; it is 320 ft tall with a diameter of 26 ft at breast height.
If you love redwoods as I do, you can add more modest sized ground-hugging varieties to your garden such as Sequoia sempervirens ‘Prostrata’ and ‘Kelly’s Prostrate’, which was named by Oregon’s own Don Howse of Porterhowse Farms nursery. Both varieties are awaiting planting in my garden this weekend.

To learn more about the remarkable trees, read on (Sources: California Department of Parks & Recreation and Wikipedia):

Redwoods blanketed much of the northern hemisphere over 100 million years ago. Ice sheets pushed the three remaining redwood species (coast redwoods, giant sequoias and dawn redwoods) into isolated patches in California and China. Only 150 years ago California’s western edge was dominated by an ancient redwood forest the size of Connecticut. Less than 3% of that original forest exists today and even that wouldn’t exist without conservations efforts begun in 1900.

Coast redwoods are dependent on a moist climate for their survival. Year round fog acts as insulation, cooling the forests in the summer months and warming them in winter. By transpiring, or “breathing out” huge amounts of moisture, coast redwoods can create their own fog. A single redwood can transpire as much as 500 gallons a day.

Although redwoods can grow from seeds, they are much more successful at asexual reproduction—layering, or sprouting from root crowns, stumps or burls. Young redwoods will sprout up from the base of a mature tree, utilizing the parent’s developed root system for more rapid growth and nutrient uptake. If a tree falls over, it will regenerate a row of new trees along the trunk so many trees naturally grow in a straight line. Sprouts originate from dormant or adventitious buds at or under the surface of the bark. The dormant sprouts are stimulated when the main adult stem gets damaged or starts to die.

The roots of a redwood are surprisingly shallow, only 4-8 feet on average with no tap root. The root systems extend out to 100 feet or more, giving stability to the surrounding ground and helping to stop erosion. Coast redwoods growing along stream channels attain the greatest size and are an important factor in keeping watersheds free from sediment.

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