The Life of an Oak

The Life of an Oak: An Intimate Portrait is written and photographed by Glenn Keator, and illustrated by Susan Bazell (1940-2012). The book was co-published by Heyday Books and the California Oak Foundation in 1998. Keator is a freelance botanist, teacher, and author here in the San Francisco Bay Area. He has taught at Merritt College, San Francisco Botanical Garden (formerly Strybing Arboretum), Regional Parks Botanic Garden (Tilden), and California Academy of Science. Keator is especially interested in identifying and gardening with California native plants. He has written many books, including the popular Designing California Native Gardens: The Plant Community Approach to Artful, Ecological Gardens. 

The first half of The Life of an Oak covers Oak Architecture, where Keator describes the ecosystem and structure of the oak tree; and Oak Life Cycle, where he describes the journey from flowers and acorns to the long-lived oak in the landscape. I don't think I've ever read a better description of Adenosine triphosphate (ATP) and its elegant process of converting sun to energy. Bazell's botanical illustrations and charts beautifully augment the text by Keator. The second half of the book covers Oak Diversity, Relationships & Evolution and Oak Habitats. I especially enjoyed Keator's description of oaks and trees that are called oaks because of similar characteristics (such as catkins and acorns) but are not genetically related to oaks. Also interesting were the descriptions of diverse oak habitats found around the world, from the Americas, to Southeast Asia, China, Australia, and Europe.

I had the pleasure of taking Keator's Mediterranean Plants ID class at Merritt College some years back, and joining his field trip to University of California, Santa Cruz Arboretum to view exotic plants from Australia and New Zealand. I was interested to learn more from his writings about oak trees in general, and Quercus agrifolia in particular, since we have a large one in our yard. I was also intrigued to learn that the oldest oak fossil ever found is from North America, but the biggest cradle of oak diversity today occurs in Southern China and Southeast Asia. I'm sure many discoveries have been made about oak genetics and evolution in the last 25 years, but I still recommend The Life of an Oak as a wonderful introduction to the mighty oak tree.

Signs of Spring

Spring has arrived here in the San Francisco Bay Area! The temperature is still cool, hovering between 65 and 70 degrees F. We've benefited from a long run of overcast skies and rain showers for several months, but now sunny skies are forecast for the week ahead. Time to get out in the garden and look for signs of spring!

A mushroom pops through the leaf duff

Another mushroom pops through the wood chips

Camellia petals for dyeing

Muscari

Asparagus bouquet

Companions

Oak tree at dusk

Passing the time until it gets warmer!

I'm gathering supplies for several projects. Seeds are on order from Renee's Garden. BeeGreen Recycling & Supply delivered several bags of potting soil along with the woodchip order. My favorite gardening tools are assembled. I'm ready for spring!

Pulling Back the Woodchip Cover

Over the last five months we've covered the old lawns and area under the oak tree with wood chips. Our landscaping plan is not to simply cover everything with mulch and walk away. Instead, we hope to improve the infrastructure by restoring and augmenting the soil. We've had some good winter rains this year which should also help.

Wood chip cover

Section 1: moist soil and healthy root (an earthworm escaped)

Is any of this actually helping the soil? This week I pulled back the woodchip cover to see what's happening underneath. I didn't know what to expect (if anything), but it can be satisfying to monitor progress. My plan was to pull aside the chips in three different sections and see what was happening "under the covers".

Section 2: loose clay soil

Section 3: decomposing wood chips

The soil was moist, which was expected since we've had several good storms pass through the San Francisco Bay Area in the last several months. In one section, the moss was no longer green (but its root mat was still intact), an earthworm raced for cover in the soil, and a nice healthy root was visible. In a second section, the clay soil broke up easily. In a third section, some of the lower-level wood chips showed a bit of fungus (I think this means decomposers are starting to work on them to break down the wood), and a bulb was pushing up through the mulch. Finally, under the bird bath, I found a little colony of white fungus (I think). I'll check again in several months to see what happens as the weather warms and turns dry. Stay tuned!

Decomposers under the bird bath

Plant Aquarium: Juniper

The junipers are thriving with the winter rains here in the San Francisco Bay Area. They do well for long periods of drought, but the little extra water is always welcome. We have two junipers on the property, one is a "big bonsai" tree that is close to the entry, and the other is a partially pruned tree that is located in the lower yard. I brought a sprig into the kitchen to display in the plant aquarium.

Juniperus californica

Junipers are in the Cupressaceae family. The California juniper is a shrub or small tree that grows to 10-26 feet (3-8 meters), and is distributed the length of California. The bark is "shreddy" and the foliage is blueish-gray and scale-like. The fleshy seed cones are like blue, waxy berries and usually contain a single seed. Male cones shed their pollen in the early spring. The juniper is typically dioecious, but a small percentage can be monoecious.

 

"Big bonsai" juniper

The juniper is ideal in a heat and drought-tolerant garden, and prefers sun to shade. It  provides habitat for native species of birds, deer and small mammals, and is a larval host for the sequoia sphinx moth (Sphinx sequoiae). The California juniper provides soil erosion control on slopes; handles dry, rocky and alkaline soil; and is used for bonsai. 

Contorted juniper bark

The junipers thrive in our yard and provide shade and privacy. They are lovely to look at and and interesting to monitor as they go through their seasonal cycles. 

Learn more:

• Wikipedia
• Jepson Herbarium
• U.S. Department of Agriculture
• U.S. Forest Service

Wood Chips Under the Oak

More wood chips! This time we're focusing attention on the area under the big oak tree. Over the years the soil has become compacted under the tree, and some its roots are growing above ground. The area is covered with a lovely green moss during the wet winter months (but is typically brown and dry the rest of the year). Our arborist recommended that a covering of wood chips would help with soil restoration.

More wood chips from BeeGreen

I ordered seven cubic yards from BeeGreen, which is quite a pile of wood chips (my previous order was five cubic yards). Luckily I had help moving all that material to the yard under the oak tree! The wood chips will help conserve moisture in the soil, as we transition to the dry summer and fall season. The chips will also break down over time, decomposing into the soil.

New wood chips under the oak in the background (older chips in the foreground)

I'm hoping for another winter rain to "water in" the new chips (maybe next week). I'm also hoping the squirrels will be able to find their acorn stashes from last fall, now that their usual landmarks are covered. From experience, I know that the birds continue to visit the bird baths and feed on insects, even with the wood chip cover. I'm sure the squirrels will adapt as well.

Wood chips in the fore- and background (a band of mossy green remains)