Thousands of tiny green shoots peek out of small pots on SFPUC-owned land near the Sunol Water Temple in the East Bay. These native plant seedlings in many ways represent the future of habitat restoration in the Bay Area. We need to delve into the past in order to understand why.
Over 15 years ago, biologists with the SFPUC’s Natural Resources and Lands Management Division watched uneasily as coast live oaks and tan oak trees on our Peninsula Watershed lands started to die in large numbers. Tests confirmed that these trees and a whole host of other native plants were under attack by more than one type of Phytophthora plant pathogen. In an effort to protect our watershed lands from further infestations of these pathogens, the SFPUC started funding research and imposing strict new requirements on the contractors and commercial growers that provided plants for habitat restoration projects on both our Alameda and Peninsula Watersheds. Despite these efforts, many new plantings in both our watersheds turned out later to test positive for these pathogens. Is this something to worry about?
Yes. There are a more than 100 species of Phytophthora (pronounced: fie-TOF-tho-ra), a genus of plant pathogens, whose name means “plant destroyer,” that spread through natural or human-assisted movement of contaminated plants, water, or soil. Well-knowns Phytophthoras include Sudden Oak Death and the potato blight that was the cause of the Irish Potato Famine in the mid 1800’s. A few of these pathogen species are quite aggressive, and once they are introduced in a watershed they are almost impossible to eliminate, all the while steadily finding and eventually killing a wide range of native plants. In fact, from 2003 to 2012, SFPUC has documented the mortality of approximately 20% of the coast live oaks and 50% of the tan oak trees on the Peninsula Watershed.
“Oaks and madrones are important keystone species in our watersheds,“ says plant biologist Mia Ingolia with Natural Resources and Lands Management Division. “I like to say they are the framing to your house. If you remove the framing, it all falls apart. So many other species depend on them, and biodiversity is a key factor in the health of a watershed.”
In response, the Water Enterprise suspended the use of container plants on watershed lands. What is an agency to do if they can no longer use commercial container plants and it needs thousands of them for the new Sunol Corporation Yard and proposed Alameda Creek Watershed Center? Build their own state-of-the-art nursery, of course.
Constructed on a one-acre plot near the location of the future Watershed Center, the design of the temporary native plant nursery incorporates the 2016 Guidelines to Minimize Phytophthora Pathogens in Restoration Nurseries as developed by The Phytophthoras in Native Habitats Work Group. The Work Group, of which the SFPUC is a member, was established in 2015, and includes representatives from most of the large land owners in the Bay Area including Golden Gate National Recreation Area, Marin Municipal Water District, Santa Clara Valley Water District, East Bay Regional Parks District, and the Mid-Peninsula Open Space District.
The temporary Sunol Native Plant Nursery is the first of its kind for the SFPUC, and one of only a few nurseries in the Bay Area to have been designed using the practices and methods of the Work Group. The nursery includes a greenhouse, a shade house, garage, small office, soil bins, water tanks, metal tables, and equipment designed to sterilize anything that might allow the spread of the pathogens. Anyone entering the nursery must be wearing clean clothes and wash their hands and shoes. Any vehicle or equipment entering the nursery needs to be cleaned and disinfected before entry. All soil for potting is steamed, plants can be no less than three feet off the ground, and they must be spaced out in order to minimize water splash between pots.
In preparation for the Alameda Creek Watershed Center and the Sunol Corporation Yard landscaping, it took biologist Mia Ingolia over a year to collect seeds from 85 different native plant species from all over the Alameda Creek Watershed. Coaxing the seeds from these different native plants to germinate required some seeds to be rubbed with sandpaper, some to be put in cold temperatures for months, and others to be placed in hot water soaks. Mia, our newly-hired Chief Nursery Specialist Bree Candiloro, and two interns gently nudged each seed to germinate and start growing.
Which takes us back to the thousands of new shoots on the metal tables in the temporary nursery, which represent more than two year’s worth of really hard work on the part of our biologists and staff. If all goes well, these little plants will be ready to be put into the ground in March as landscaping around the new Sunol Corporation Yard, which is under construction now as part of the Sunol Yard Long Term Improvements Project. Should it prove successful to grow pathogen-free plants for the Sunol Corporation Yard and Alameda Creek Watershed Center, we will consider continuing our efforts to provide native plants for restoration and mitigation projects in the Alameda and Peninsula watersheds.