Air Spade

Soil compaction results when soil particles are squeezed together, eliminating air space. This makes it harder for water and air to infiltrate the soil, and for roots to grow and take up water and minerals. While researching methods of restoring compacted soil in Soil Restoration Under the Oak, I came across an arborist tool called an air spade (also known as an air knife). 

The air spade is powered by an air compressor, and moves soil away from tree roots at super-sonic speed without damaging the roots. The video shows several tree care applications, including vertical mulching around marker 0:54, and soil aeration around marker 2:25. Note that this is not a product promotion, just a very informative video. You can find more examples by searching the Internet using a variation of "air knife for arborists".

In our case, our arborist did not recommend something as powerful as an air spade, since the compacted soil under the oak tree is not in a foot traffic area. The wood chips are sufficient to start.

Learn more:

• Keeping Native California Oaks Healthy, by Bruce W. Hagen, Forest Pest Specialist, Forest Pest Management Program. California Department of Forestry and Fire Protection, Tree Notes, Number 7, June 1990.
• What is a Super-Sonic Air Knife, by Conner of Root Cause Seattle (video).
• AirSpade for Arbor Applications

Horse Bedding

This fall we're working with our gardener and a landscape consultant to enrich the soil in our yard. We recently received a delivery of about 12 cubic feet of horse bedding from a nearby stable. It is comprised of the chips and straw used to line the stables, and horse manure, and is a coup for our Soil Restoration project. 

About 12 cubic feet of horse bedding

We postponed its delivery until the heat wave and forest fire smoke had subsided, and cooler weather arrived. Surprisingly the bedding has no unpleasant odor. Instead, it has a mild, earthy smell that is quite pleasant and natural. 

Horse bedding is gold for the soil

Our landscape consultant spread some of the bedding on a section of the old lawn that has lost all of its topsoil. The wood chips will protect the compacted soil, and eventually break down. The manure, which contains some of the nutrients (nitrogen, phosphorus, and potassium) that animals consumed, will also break down and become incorporated into the soil. 

Horse bedding on the old lawn

Horse bedding under camellia shrubs

He spread another batch of the horse bedding under the camellia shrubs that are in the back of the house. A nearby Japanese maple and magnolia tree will also reap the benefits. This enriched mulch will contribute to the process of process of soil restoration, especially when the winter rains start in a month or so.

Soil Restoration

 I'm afraid we've neglected our garden for too long. Between trips to Seattle, Alaska, and the desert, explorations in the regional parks, and researching and filming "plants to dye" for projects, our yard has suffered (but no regrets for all that life lived!). Add a long drought several years back, a broken sprinkler system, and a rigorous career, and things are looking a little ratty. Part of this was intentional – the first phase of converting from a water-thirsty garden from yesteryear to a modern native plant and wildlife friendly garden. The idea was to practice survival-of-the-fittest gardening for awhile, and see what survives!

Brown, compacted lawn

We'll start with the remaining bones of the original garden, and work from there to create the next phase of the garden's life. I actually like what remains - the oak tree is a major focal point. The native toyon, hawthorn, and prunus shrubs in the lower yard are holding their own, and provide a screen and sound barrier for busy traffic and a habitat for birds. The junipers and sedges are also healthy. The camellias are a little leggy and scruffy (but may be at the end of their life cycle). The pittosporum and tulip tree by the fence look pretty good (their roots may be pirating water from our neighbor). The lawns are brown most of the year, but the embedded moss typically greens up in the rainy season and looks quite beautiful. Quite a few flowers come up in the spring from spring rains.

On the negative side, the soil where the lawns once thrived is compacted and needs restoration. So does the soil under the oak tree (carefully). We're teaming up with our maintenance gardener, and a gardening consultant who has helped clients all over the Bay Area with their gardening projects. One of our first steps is to bring in mulch, organic matter, and fertilizer to enrich the soil. We're looking forward to the transformation, and will keep you posted!

Marra Farm Community Garden

On one of our long rambles in South Park, Seattle with Mako, we passed through Marra Farm, a four-acre farm parcel that is part of Marra-Desimone Park. The original Marra Farm was operated as a truck farm by the Italian-American Marra family from the early 1900s to the 1970s, and was then sold to King County.

Marra Farm community garden in South Park, Seattle

In 1997 several citizens and nonprofit organizations restored part of the farm, and today it operates as a community garden, growing more than 13,000 pounds of organic produce a year. Seattle residents can sign up for a P-Patch lot, and are added to the waiting list.

Healthy kale and greens at Marra Farm

Greenhouse structures at Marra Farm

We walked through the raised garden beds and green houses. It was December, cold, and raining, but the kale looked fantastic! The large chicken coop was stocked with many species of chickens.

Chicken coop at Marra Farm

Another restoration project is underway nearby – Hamm Creek, a tributary of the lower Duwamish River which empties into Elliott Bay. According to Habitat Restoration along the Lower Duwamish Waterway, the restoration at Hamm Creek provides a “fish-passable” connection to the Duwamish river, enabling salmonid spawning in Hamm Creek.

Hamm Creek habitat restoration

Volunteering in the Regional Parks

Being grateful and counting your blessings is one way to make you feel better in tough times; another way is to do something for someone else. Volunteering your time is a great way to do something for others. The San Francisco Bay Area has many volunteer opportunities – serving food in a homeless shelter, working with at-risk youth, leading tours as a docent in a museum or gallery, or raising funds for scholarships or charity. Another option is to volunteer your skills and labor at a historical, botanical, or non-profit garden. With funding being cut at every level of government, organizations rely heavily on volunteers. You can help.

Non-native ice plant, brought in for freeway plantings, has "travelled" and
become invasive at Crown Beach in Alameda.

I spent a Saturday morning volunteering for the East Bay Regional Park, at Crown Beach in Alameda. I worked side-by-side with two high school students – one was an exemplary exchange student from Germany, another was a local student doing community service while reflecting on some poor choices. Together we faced the challenge of removing invasive, non-native ice plant from the beach. We worked out a system and removed 70 bags of plant material. At the end of four hours, I was exhausted, but I think we made the world a better place. Learn more: http://www.ebparks.org/getinvolved/volunteer.

Bags of ice plant removed from Crown Beach.

Trees at Mills College

My Arboriculture class from Merritt College visited Mills College to learn how to evaluate trees (mature trees can add thousands of dollars to the price of a home), and how to assess trees that present a danger. Our guide was Judy Thomas, who worked at Merritt College for many years, developed much of its landscape horticulture curriculum, and now works as a professional tree evaluator. Our class was fortunate to have the opportunity to see the historic campus, known for its botanical collection and heritage.

Rothwell College Center at Mills College

Tree-lined path that follows Richards Road into the campus

Mills College was founded in 1852 as a Young Ladies’ Seminary, originally in Benicia, California, and then moved in 1865 to its present site in the Oakland foothills with the new name Mills College. The college developed a collection of native and exotic plants. In 1919, Mill’s botany professor, Howard E. McMinn, wrote A Manual of Trees, Shrubs and Vines of Mills College Campus, which provides plant identification for its 263 species collection. The book was updated in 2011 (both edititions are available on Amazon: http://www.amazon.com/s?ie=UTF8&rh=n%3A283155%2Ck%3Amanual%20trees%5Cc%20shrubs%20vines%20Mills%20College%20Campus&page=1).

Leona Creek restored with native plants



A Eucalyptus tree that still remains

Mills College worked with Robert Sabbatini, ASLA, from 2006 to 2009 to update their landscape. They developed the Mills College Landscape Heritage Plan, which embraces current ideas in landscape architecture, and retains the College’s sense of place and botanical history. Part of this plan included restoring Leona Creek, which courses through the property, and replacing a landmark double-row of blue gum Eucalyptus trees, planted a hundred years ago, with another type of tree. To view the plan: http://www.sabbatini-loyd.com/r-Mills-Summary.pdf.