Oak Patrol

Going on oak patrol is a recurring activity every spring, here in the Oakland Hills. Oak patrol means looking for oak seedlings in the yard and uprooting them (see Spring Spruce Up). Every fall the the squirrels and birds stash acorns all over the property in preparation for winter. By spring they've eaten most of them, and forgotten many. Those forgotten start to sprout in response to the winter rains. I love our mighty oak, but the little patch of land is too small to sustain a mixed oak forest! Out they come.

Oak patrol

The futility of cutting off an oak sprout

Over the years we've learned that cutting sprouts off at the soil is not enough. The oak sends down a strong root straight into the ground, and sends out new shoots every spring. The whole seedling must come out or you'll be revisiting it next year!

Interesting oak galls

This year I found a whole groups of sprouts with various shapes of oak galls. We've enjoyed seeing oak galls, or oak apples, on our rambles in the Bay Area see Summer on the Iron Horse Trail, Clear Lake Plant Diseases, and Finished Plant Diseases. Plus, oak gall is a mordant for cellulose-based fibers because of the tannin, as described in Mordants and Fixatives. I recently spotted a few more oak seedlings in another area of the land, so there is more oak patrol work to be done!

Plant Aquarium: Oak

Our big oak has received some extra attention this year - some fairly good rains, a covering of wood chips within the dripline, and a visit from our arborist. We recently had a heat spell that propelled the temperature to the high 70s during midday, followed by the oak dropping quite a few leaves overnight (all of which are dry and brown). Glenn Keator in The Life of an Oak: An Intimate Portrait describes this process of live oaks periodically dropping old leaves, typically in conjunction with a change in day length and a combination of chilly nights and warm days. The oak is also putting out new growth, and releasing yellow pollen that covers the patio furniture and cars in the night.

Quercus agrifolia new growth

Oaks are in the Quercus sub-family of the Fagacea family. Quercus is native to the Northern Hemisphere, and includes deciduous and evergreen species. Its range spans the Americas, Asia, Europe, and North Africa, and includes cool temperate and tropical latitudes. Quercus agrifolia, also known as "live oak" or "coast live oak", grows west of the Sierra Nevada mountain range from Mendocino County, California, south to northern Baja California in Mexico. Live oaks thrive in the coastal environment here in the San Francisco Bay Area.

Oak canopy

Both birds and squirrels stash acorns throughout the yard. They go to great lengths to keep their stashes hidden, sometimes digging them up to hide again. In the spring we are continually on "oak patrol" to pull up the seedlings from nuts that were not eaten during the winter.

Acorn seedling

The oak is a focal point in our landscape, and provides shade, beauty and habitat for birds, squirrels, moths and so forth. Ours is in a precarious position, located on the fenceline, and with its roots wedged between two utility boxes streetside. Still, we try to take care of it as well as we can to ensure that it thrives for years to come.

Learn more:

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

 

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.

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)

Soil Restoration Under the Oak

 The soil under the oak tree needs some help. The soil has compacted over time, and some of its roots are exposed above ground. The root zone is not a foot traffic area, but over time, gravity and natural drainage have eroded and compressed the soil. We stopped irrigating the area years ago. The lawn died, and was replaced with moss (beautiful during the rainy winter season, but less so during the dry summer months). It's good that we stopped watering, since too much water during the warm season invites disease for oaks.

Majestic oak tree trunk and limb

I scheduled a consultation with our arborist from Brende and Lamb to discuss the health of our oak tree, and get the scoop about soil restoration. Our landscaper had expressed concerns about several small cavities and cracks in the bark at the base of the tree. We've been letting the oak leaves collect under the tree in a natural duff to jump start the soil restoration process. I wondered whether we could do more, such as bring in a load of wood chip mulch (see Wood Chips Everywhere!), or aerate the soil using a soil aerator or an air spade (a.k.a, an air knife). I also wanted to discuss irrigation, since we have plans to modernize our old, broken system.

Small cavities in the oak bark go back several inches

Our arborist has been monitoring and pruning our oak for years. He opined that the cracks in the bark were part of the natural growth pattern, and that the small cavities were probably fine since they did not harbor standing water. Limb attachments in a v-shape are more worrying, since they can trap moisture that can lead to rot (versus u-shaped attachments, where water rolls off more easily). He recommended that we bring in wood chip mulch to protect the soil, and encourage its restoration. He also recommended that under our big trees, a soaker hose  is a good irrigation solution (even oaks appreciate an occasional (monthly) drink of water during the hottest months).

Ridges and roots under the oak tree

Optionally we could aerate the soil. He thought the air spade would be overkill, since our oak is not in a high traffic area. But he described a method of using a deep-root irrigator to create holes in the soil, and then filling them with organic mulch to enable the exchange of oxygen in the soil. Many tree services offer the service, but it would be quite expensive for the area under our oak. Instead he recommended doing it ourselves - chipping away at it over time, especially during the rainy season when the soil is typically moist. It's a pleasure to meet with someone who knows and loves trees. We now have the information we need for the next steps!

Wood chips in the foreground, and leaf duff beyond

Dry Creek Garden

On one of our hot, summer weekends, my husband and I visited Dry Creek Garden in Union City. It is part of Dry Creek Pioneer Regional Park, and closely associated with Garin Regional Park in nearby Hayward. The Meyers sisters (Edith, Mildred, and Jeanette) donated 1200 acres from Dry Creek Ranch to the East Bay Regional Park District to create Dry Creek Pioneer Regional Park.

Nearby wheat field

Dry Creek Pioneer Regional Park

Their father, Henry H. Meyers (1867-1943) was an architect here in the Bay Area, and designed some landmark sites such as the Posey Tube, Highland Hospital, and Caldecott Tunnel. He also designed the family home in Alameda – Meyers House and Garden.

Gate post for Dry Creek Cottage

The three daughters were successful in their own right. Edith (1900-1971) became a pediatrician, and served as staff president at Children's Hospital. Mildred (1898-1982) studied architecture at U.C. Berkeley, passed the state exam in 1926, practiced with her father until his retirement in 1936, and then took over the practice. Jeanette (1905-1993) ran Dry Creek Ranch.

Fountain in the wild

Shady path through the oaks

My husband and I spent a leisurely hour in the shady Dry Creek Garden. We followed meandering paths, crossed charming bridges, explored the kitchen and rose gardens, enjoyed watching the free-range chickens forage for food, and sat on on various benches to observe nature.

Chinese lantern	Free-range chickens
Flower garden	More flowers

The two-acre garden is rather wild and tangled, with many interesting native and exotic plants and trees. Dry Creek is lined with wonderful stonework, and, unexpectedly, contained some water. Meyers Cottage is very charming and set in a shady stand of trees. It's easy to see why the Meyer family would gravitate to Dry Creek as a summer home.

Meyers Cottage surround by trees

Dry Creek (with a little water)

Follow the May Trail through shady oaks to access a 27-mile network of trails. Take the Ridge Loop Trail or the High Ridge Loop Trail for the views. Take the Dry Creek Trail for a mile to the southern tip of Jordan Pond in Garin Regional Park. Be sure to close the gate, since these hills are still used for cattle!

Cattle gate

Dublin Heritage Park and Museums

Dublin Heritage Park and Museums is a ten-acre park located in the crook of the Interstate 580 freeway as it swings around from the valley floor to make the grade through the pass heading west toward the East Bay. It is a gem of a place to spend an hour or two if you're in Dublin, California, and want to be transported back in time a hundred years or so. The location was  the original "downtown Dublin" for the surrounding homesteads. As Dublin transformed from farmland to a modern town, a few forward-looking folks sought to preserve a little of its dairy farming history.

Dublin Heritage Park and Museums

The old St. Raymond Church (built in 1859) and the Dublin Pioneer Cemetery (established in 1859) are in their original locations. The Murray Schoolhouse, Kolb House, and associated barns were moved from across the freeway as the original farms were carved up for development projects. A small stream and forest insulates Heritage Park from the freeway, and the grounds are landscaped with plants you might see in the early 1900s, like hollyhocks and rambling roses. Across the street is the Challenge Dairy headquarters, and the original Green general store building.

The schoolhouse has wonderful exhibits for kids (and grownups) showing what it was like to attend school in a one-room schoolhouse, and to live and work on a dairy farm. The headstones in the cemetery provide a glimpse into pioneer life, and the church is a testament to early settlers who pitched in to build the center of spiritual and community life. I especially enjoyed our personal tour of the Kolb House, built in the Craftsman Bungalow style that was becoming popular at the turn of the twentieth century. I recommend visiting the Dublin Heritage Park and Museums, and checking out the photographs at the Online California Archive, the Dublin Heritage Museum collection.

Discriminating Squirrels

Last fall, I noticed the squirrels were leaving many acorns from our Quercus agrifolia on the ground, rather than stashing them. Typically they grab nuts as soon as they fall, scamper to a hiding place, glance around, and then quickly bury the nut. Sometimes they double-back, dig up the nut, and rebury it somewhere else. Instead, they were ignoring many nuts, and burying only a few.

Acorns from Quercus agrifolia in the Bay Area.

Naturally, this behavior change caught my attention. My folks were visiting from Alaska, so we launched an investigation. The first thing we noticed is that almost all of the ignored nuts had a bore hole in them. My dad split open a healthy nut, and several nuts with bore holes. The unhealthy nuts were filled with frass, but no inhabitants.

Acorn with a bore hole.

Two insects that target acorns in the San Francisco Bay Area, are filbert worms (Cydialatiferreana) and several species of filbert weevils (Curculio spp.). After mating in spring, the female filbert weevil drills a small hole in an immature acorn, and inserts her eggs; the female filbert worm lays her eggs on the outside of an acorn, and the larvae bore into the nut. In both cases, the larvae develops and feeds in the acorn, leaving its frass; and then bores out in the fall, moving to the soil until spring. The number of infected acorns varies by year, environmental conditions, and the individual tree. The infestation does not harm the tree, but the acorns are infertile.

Left: healthy acorn. Middle and right: infested acorns.

Interestingly, birds and squirrels can discriminate between the healthy and infected acorns. Much like humans, they separate the infested nuts, and preserve the healthy!

Learn More:

• Filbert Pests in Live Oaks (prepared and edited by John M. Harper, Richard B. Standiford, and John W. LeBlanc)
• Pests of Acorns (prepared and edited by Richard B. Standiford and Pamela Tinnin)

Spring Spruce Up

Spring is a great time to get out in the yard, and get things spruced up for summer. Here are a few things I like to do in our Bay Area yard.

Get out the pruning shears, and cut back some unruly growth. These sharp shears are especially useful on the small maples and rhododendron bushes. They are light weight and easy to use.

Pruning unruly growth

Go on “oak patrol.” The uneaten acorns stashed by squirrels in the fall start to sprout, and some of sprouts I’ve missed in previous years really start to take hold. I love the mighty oak tree in our front yard, but multiple oaks are just not sustainable in our tiny yard.

Oak patrol to remove acorn sprouts

Add organic material to the soil, replenish the raised bed with organic material, and maintain the drip system. Every year I am optimistic about planting a small vegetable garden, even though the neighborhood deer are the ones to benefit.

Add organic material and check the drip irrigation system

With the yard spruced up, it is time to fire up the charcoal grill. I have a few new grilled vegetables recipes to try, and might even try using the pizza stone (although I hear it is difficult to keep the heat up using charcoal).

SOD Blitz Partnership

I love the idea of the SOD Blitz partnership between the UC Berkeley science community, the USDA Forest Service, and “citizen scientists” to gather data on Sudden Oak Death. A similar idea has been used to gather information about migration of birds, butterflies, and fish. It also reminds me of the crowdsourcing projects run on the web, using members of the online community to solve complex problems.

Tip blight symptoms on tanoak caused by P. ramorum. Photo by Joseph
O'Brien (Creative Commons Attribution 3.0 License).

SOD Blitz participants are trained to look for symptoms, and to conduct testing on  specimens. The SOD Blitz project website provides information on training dates, symptoms, testing, and meetings.  The 2014 Spring SOD Blitz is currently being organized, so the training schedule has not yet been published. If you are interested in participating in a Blitz, check the website regularly for updates. In the meantime, there are plenty of workshops and lectures scheduled for Fall 2013.

SODMAP App

A free SODMAP application, with SOD Blitz research information, is available as a plugin to Google Earth. It can be installed on the desktop or on smart phones (Android and iPhone). The application shows you visually where SOD Blitz specimens were taken, and the test results. SODMAP categories include infected and uninfected trees, oaks, tanoaks, and water samples.



SODMAP application running on a desktop computer. Click on an icon to drill down to detailed information.

Icons on the map represent either a single record for one of these categories, or multiple records. Drill down to view detailed information, or to see multiple records and their details. Some trees are tagged, and checked every year. Others are sampled randomly from year to year.

This icon indicates a SOD infected tree - here a bay laurel (Umbellularia californica).

On smart phones with GPS, you have the added capability of the app identifying where you are, and automatically displaying details for your surroundings. This is great if you are out in the field. Currently I have SODMAP running on my desktop and iPad, and really enjoy scoping out the results of the San Francisco Bay Area SOD Blitz. 

The icon indicates a SOD infected oak or tanoak tree - in this case live oak (Quercus agrifolia).

SOD Blitz 2013

I recently attended a lecture at University of California, Berkeley (UC Berkeley, or Cal) by Dr. Matteo Garbelotto, to summarize the results of the 2013 SOD Blitz. Dr. Garbelotto is an adjunct professor at UC Berkeley. He received his B.S. and M.S. degrees in Forestry from the University of Padua, Italy, and then completed his graduate and post-graduate work in forest pathology at UC Berkeley. He has been studying SOD since its discovery in California, and is an engaging speaker, making information accessible for both scholar and community. Fittingly, the lecture was held under a mature oak tree outside Tolman Hall on the UC Berkeley campus.

SOD Blitz—or Sudden Oak Death Blitz—refers to an event where professionals and trained “citizen scientists” join forces to fan out over Northern California, look for evidence of Sudden Oak Death, and gather specimens. The specimens are tested and analyzed in the lab. In this way, a lot of field data has been gathered in the last six years to study the introduction and spread of SOD in California. Data is published online, and available via a free app for Android or iPhone. Professionals include USDA Forest Service and the UC Berkeley Forest Pathology and Mycology Laboratory. SOD Blitz also refers to community outreach to inform the community about Sudden Oak Death.

Symptoms of ramorum leaf blight on California bay laurel. Photo by Joseph
O'Brien (Creative Commons Attribution 3.0 License).

Several items interested me. In general, the overall infection rate of tanoaks and live oaks decreases after a dry year, and then spikes after a wet year. However, a comparison between 2012 and 2013 research shows some deviation - increases were observed in two colder areas, and decreases in hotter areas. This supports observations that the disease operates differently between coastal forests and inland forests. Infestation typically happens during the spring rains (March, April, May), and not the early rains in November, December, January, February), so you should avoid pruning during spring rains.

Plants such as bay laurel, Rhododendron, and Camellia are intermediate hosts for Phytophthora ramorum; removing them from the presence of a high value oak can reduce chances of its infection. Use of phosphonate to treat healthy oaks is very promising, but they are reevaluating delivery mechanisms, since plugs may cause damage to the trees. Additionally, Dr. Garbelotto observed that the disease is relatively slow moving, which is giving scientists a chance to study it. These lectures are offered periodically and well worth your time.

Clear Lake Plant Diseases

I’m afraid my Plant Diseases class from Merritt College in Oakland has despoiled me – I am always on the lookout for plant diseases! End-of-summer is a great time to spot them, as many plants have spent their reserves on reproduction, and are more vulnerable to attack. Here are some of the diseases I spotted in Clear Lake; oaks seem especially hard hit.



Sudden Oak Death –  I wasn't close enough for direct inspection, but this looks like SOD from afar; caused by the water mold, Phytophthora ramorum. 

Oak Gall – these little "nipples" are galls caused by asexual reproduction by the oak gall wasp.
When the wasp lays its eggs, hormones kick off a type of genetic engineering to create the perfect nursery (the gall).

Oak Apple Gall – this "strange fruit" indicates sexual reproduction by the oak gall wasp.

Tent Caterpillar – we found these gauzy structures all over foliage.
The residents had already moved on.

In many cases, these diseases do not cause permanent damage. An organism is simply taking advantage of a situation, and working through its own life cycle. After the class, seeing plant disease is not necessarily alarming. Plants in nature are rarely perfect; instead, they are teaming with all sorts of life forms. Learning to enjoy the whole ecosystem of a plant, both good and bad, can add to the enjoyment of nature as well as the garden. And raising your tolerance for imperfection can lower the need to combat the imperfect with pesticides.

Lake County

My husband and I had the opportunity for an end-of-summer visit to Clear Lake in Lake County, about 90 miles north of the San Francisco Bay Area. Clear Lake is the largest natural fresh water lake (43,000 acres) in California. It is located inland, and is accessible from both Interstate 5 and Highway 101. The whole area is an ancient volcanic field, with the dormant Mount Konocti (3,200 ft.) located near the southwest shore of the lake. The Geysers steam field is tapped by geothermal power plants to provide electricity. The soil is rich from ancient volcanic ash, and very productive. The climate is mild, sunny, and typically fog-free.

Clear Lake - classic golden hills dotted with oaks

Lake County region is in Climate Zone 7 - California’s Gray Pine Belt  in the Central Valley (or incense cedars to the north and south). According to Sunset, Zone 7 is characterized by hot summers and mild winters, with sharply defined seasons yet without severe winter cold or humidity. Plants that require a distinct seasonal pattern thrive, such as flower bulbs, peonies, lilacs, and flowering cherries. Deciduous fruit trees also do well, such as apples, cherries, peaches, and pears. Typical winter lows range from 35 to 26°F (2 to –3°C), with record lows averaging from 18 to -0° F (–8 to –18°C).

 

Clear Lake - shoreline wetlands

I loved the contrast of the classic golden hills dotted with oaks, the lush shoreline, and the productive farms and wineries, all in close proximity. We enjoyed learning about the geology of the area, visiting wineries, purchasing fruits and vegetables from roadside stands, and eating a delicious dinner of local ingredients in the town of Clear Lake. The area reminded of me of Napa and Sonoma, but without the crowds, congestion, and commercialization.

Clear Lake - productive farms and wineries

Hearst Castle Gardens

The Renaissance Revival style often includes lush gardens, and Hearst Castle is no exception. As we know from our exploration of garden history, structures and garden form a unified whole in the Renaissance style.

Structures and gardens complement each other in a unified design

Julia Morgan and William Randolph Hearst designed the gardens to be in bloom year round, using native and Mediterranean climate plants. Roses, Rhododendron, and Hydrangeas thrive on the sunny hilltop, as does the Bougainvillea that grows on the guest houses. You can find the fragrant “Peace climber” rose growing on several structures and trees.

Roses and hydrangeas flourish in full sun

Playful marble statue - maiden feeding an ear of corn to a lamb

Morgan and Hearst incorporated native Coastal Live Oaks (Quercus agrifolia) into the garden design – sometimes changing plans to work around an existing tree, other times moving an entire tree and its root structure to a new location.

Stately Coastal Live Oak that provides shade and habitat

Other trees found in the garden include Cryptomeria (a deciduous Redwood), Yews, Cypress, Stone Pine, Deodar Cedar, various palms, and fruit trees.

A variety of trees, flowers, and hedges

Japanese boxwood is used as a low hedge, and as a parterre to boarder planting areas.



Boxwood parterres

Terraces provide places to gather, and to enjoy the spectacular “borrowed” view of the hills, coast, and Pacific Ocean.

Formal terrace with a fabulous view

Wide rustic terrace surrounded with pines and palms

 The Esplanade is a wide walking path around the hilltop. It is lushly planted with flowers, and provides afternoon shade.

Orange trees line the Esplanade