Yardsmart: Planting redwoods

Maureen Gilmer

The vast redwood forests of Northern California's coastline are mystical. It is dark and romantic beneath these evergreen canopies, where I wandered during my early years in horticulture. There in the gloom, shelf fungi and mushrooms festoon old-growth stumps and disintegrating trunks that add to the gradual buildup of organic matter on the forest floor.

This was where I first encountered giant woodwardia ferns and rhododendron occidentalis in bloom wherever significant light penetrated the canopy. Even in these second-growth forests that rose up in the wake of 19th-century logging, the redwood trees are awesome in their beauty. It is here that I learned firsthand what Sequoia sempervirens desires to grow just about anywhere winters are no colder than 5 degrees F.

While the north coast can experience enormous winter rainfall, it will be dry from May to November, without any summer moisture.

Coast redwood is a native tree that proves one of the most well-adapted to container culture both at the growers' and retail garden center. Many other natives are finicky about their roots and may be difficult to grow and maintain in containers over time. Despite the enormous size at maturity, redwoods lack a tap root in favor of moderately sized roots to just 10 feet deep. Their strength is, instead, due to a network of fibrous surface feeder roots that feed upon decaying organic matter at the bottom of the duff layer that builds up on the forest floor. Feeder roots are such active travelers that they invade mulch or soil stockpiles and have been known to work their way up into raised beds.

This demonstrs while still very young. The duff layer, composed of dead leaves, cones and twigs, is the equivalent of an equal amount of mulch. Provide this for a young tree and the surface feeder roots thrive, spreading out in cool, moist ground protected by dufflike surface mulch. It explains why redwoods do better in groups of three or more, closely spaced trees, than they do as an individual specimen. The canopies shade each other's roots and provide greater accumulations of litter that acidifies the soil underneath so it's ideal for feeder roots to draw from.

When planting redwood trees, add a good deal of compost to the soil backfill to lure feeder roots beyond the rootball. Select compost rich in aged forestmpost rich in aged forest byproducts for ideal PH, and to introduce important microbes found in coniferous forests everywhere. After planting, immediately mulch the soil surface with a similar compost or planting mix, which may be largely woody matter. Spread it all the way to the outer tips of the branches, a point known as the drip line. Rooting will always be greatest within the drip line, and watering the entire zone is crucial to reaching the entire root system.

Don't pack down the mulch. Leave it light and fluffy. Add more coverage each year in spring to ensure that there's enough in place to protect roots over the summer.

If you walk in the redwood forest over natural duff, you can feel how naturally springy it is. This is due to the stiffness of the redwood leaves and twigs, which are very slow to decompose. This open texture ensures that rain or irrigation water moves through quickly to reach the soil where feeder roots lie waiting. Pack your mulch too tightly and rain or irrigation may not penetrate as well, instead running off well beyond the drip line.

When your redwoods grow older, add wood chips to your mulches. With the trees having such a thick layer augmented by their own natural litter, you'll be able to walk beneath the branches and feel what it's like in those legendary redwood forests.

Maureen Gilmer is an author, horticulturist and landscape designer. Learn more at www.MoPlants.com. Contact her at mogilmer@yahoo.com or P.O. Box 891, Morongo Valley, CA 92256.